Instrumental and Sensory Characteristics of a Baked Product Containing Barley Flour with Varying Amounts of Beta-Glucan and Sugar Substitute

by

Niti Lathia

A Thesis submitted to the

Graduate School-New Brunswick

Rutgers, The State University of New Jersey

in partial fulfillment of the requirements

for the degree of

Master of Science

Graduate Program in Food Science

written under the direction of

Dr. Henryk Daun

Dr. Paul Takhistov

and approved by

________________________

________________________

________________________

New Brunswick, New Jersey

October 2011

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ABSTRACT OF THE THESIS

Instrumental and Sensory Characteristics of Baked Product Containing Barley Flour with Varying Amounts of Beta-Glucan and Sugar Substitute

By Niti Lathia

Thesis Directors:

Dr. Henryk Daun

Dr. Paul Takhistov

The objective of this study was to determine the influence of varying levels of

beta-glucan in barley flour on selected properties of a model baked product. Another aim

was to reduce sugar levels in the product by incorporating a natural sweetener stevia and

to monitor its influence using instrumental and sensory analysis. Batter rheology was

studied using a lubricated squeezing flow technique, pasting profiles of the barley flours

were determined with a rheometer, viscoelastic properties were evaluated using dynamic

oscillatory rheology to measure G’ and G”, and firmness of the baked products was

monitored using a texture analyzer, for changes occurring due to varying β-glucan levels

in barley flour and removal of sugar. L a* b* color values of barley flour and muffins

were obtained using a colorimeter. A descriptive sensory panel was trained to observe

changes in product attributes when stevia was used to replace sugar in the high beta-

glucan product.

Water absorption index was found to be significantly higher for high β-glucan

barley flour. The color of both barley flours also had a significant difference in L*

(lightness) and b* (yellowness) values. Similarly, muffin samples prepared without

sugar, using stevia, were significantly lighter in surface color (higher L*), while the

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interior colors were darker (higher b*). Low beta-glucan dough showed a lower biaxial

extensional viscosity compared to the high beta-glucan dough, which indicates that the

level of beta-glucan present in the barley flour has an impact on the dough viscosity. The

pasting profiles of the flours were also found to be significantly different, where the high

beta-glucan barley flour resulted in a significantly higher peak viscosity but lower peak

time compared to low β-glucan barley flour. Muffin firmness was found to be

significantly higher when sugar was omitted from the formulation, but there was no

significant difference in firmness among the two beta-glucan levels in the muffins. The

sensory descriptive panel found significantly higher firmness, surface roughness, and

bitterness attributes for the high β-glucan muffins prepared with stevia. Additional

efforts will be needed to mask the undesirable attributes in the model baked product

occurring due to the removal of sugar.

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Acknowledgement

First and foremost, I would like to express my sincere gratitude towards both of

my thesis advisors, Dr. Henryk Daun, who brought the project to my attention, and

equally to Dr. Paul Takhistov whose lab I conducted my research in. Both professors

have provided guidance, support, encouragement, and have had patience in explaining

my numerous inquiries throughout the duration of my project research. Secondly, I

would like to thank Dr. Kit Yam for being on my thesis defense committee, whose input

and suggestions I value. In addition, a big thank you to my lab mates for their assistance

with learning new instrumentation as well as providing a fun learning environment.

Also, I appreciate the efforts of the undergraduate team of students that participated in the

sensory portion of this research as panelists; your help and cooperation was greatly

appreciated.

Most importantly, I would like to thank my parents and family for providing the

financial support for my graduate studies as well as love, encouragement, moral support,

providing comfort during the challenging times, and accepting my absence while I

worked towards completing my degree. I have relied on them for guidance and strength

throughout my academic career. Thank you for your confidence and unwavering support.

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TABLE OF CONTENTS

Page

ABSTRACT OF THESIS ii-iii

ACKNOWLEDGEMENTS iv

TABLE OF CONTENTS v

LIST OF ABBREVIATIONS vii

LIST OF TABLES viii

LIST OF ILLUSTRATIONS ix

LITERATURE REVIEW – CHAPTER ONE

1.0 Introduction 1

1.1 Health Benefits of Barley 4

1.2 Chemical and Physical Characteristics of Barley 10

1.3 β-Glucans and Arabinoxylans 13

1.4 Properties and Molecular Interactions among Major Food Components 17

1.5 Beta-glucan extraction 17

1.6 Water absorption capacity and effect on end-products 19

1.7 Rheological Properties Influenced by barley flour beta-glucan content 21

1.8 Stevia as a Sweetening Agent in Consumer Products 22

1.9 Conclusions from Literature Review and Objectives for Research 24

MATERIALS AND METHODS – CHAPTER TWO

2.1 Ingredients Used in Baking Procedures and Analytical Measurements 26

2.2 Water Absorption Index of Low and High β-glucan Barley Flour 27 2.3 Microbakery Model Formulations for Barley Muffins 29

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2.4 Rise and Moisture Loss of Muffins 32

2.5 Rheological properties of barley dough using lubricating squeezing flow technique 33 2.6 Pasting Properties of High β-glucan and low β-glucan barley flours 36

2.7 Dynamic Rheological Properties of Muffin Batter 39

2.8 Assessing Muffin Firmness Using a Texture Analyzer 40 2.9 Evaluation of Colors Using a Colorimeter 42

2.10 Nutritional Comparison of Muffins 44

2.11 Sensory Methodologies Used to Evaluate Muffin Products 45

RESULTS AND DISCUSSION – CHAPTER THREE

3.1 Water absorption values for barley flours 50

3.2 Increase in Muffin Heights After Baking 51

3.3 Muffin Moisture Loss After Baking 53

3.4 Rheological Properties of barley flour doughs and muffin batters 55

3.5 Pasting properties of barley flours 62

3.6 Color values for Barley Flour Varieties 64

3.7 Muffin Surface Color 66

3.8 Muffin Interior Color 71 3.9 Muffin Firmness 74 3.10 Nutrition Facts for Muffin Formulations 77

3.11 High β-glucan Muffin Sensory Quantitative Descriptive Analysis 79

3.13 Conclusions and Suggestions for Future Work 85

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LIST OF ABBREVIATIONS

United States Department of Agriculture (USDA) National School Lunch Program (NSLP) National Health and Nutrition Examination Survey (NHANES) Dietary Reference Intakes (DRI)

Recommended Daily Allowances (RDA)

Coronary Heart Disease (CHD)

Low density lipoprotein (LDL)

Food and Drug Administration (FDA)

Code of Federal Regulations (CFR)

Apparent Biaxial Extensional Viscosity (ABEV)

The International Commission on Illumination (CIE)

Rapid Visco Analyzer (RVA)

Quantitative Descriptive Analysis (QDA)

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LIST OF TABLES

Table 1: Nutritional Composition of Sustagrain Barley Table 2: Average Nutrient Comparison for Hulless Barley, Oats, and barley variety Prowashonupana (Prowash) Barley Table 3: Formulations for Muffin Batters Used to Prepare a Model Baked Product Table 4: Reference standards for selected attributes used in Spectrum Descriptive Analysis panel Table 5. Descriptors used to evaluate muffin samples in the QDA panel Table 6: Water Absorption indices of high and low β-glucan barley flour Table 7: Percentage Increase in Muffin Height (Rise) After Baking Table 8: Percentage Decrease in Muffin Weight (Moisture Loss) After Baking Table 9: Pasting profile for low and high β-glucan barley flours Table 10: Consistency index and flow behavior index for muffin batter with varying amounts of beta-glucan and sugar Table 11: Average L a*b* Values for low β-glucan and high β-glucan Barley Flour Varieties Table 12: Average L, a*, b* color values for surface color of muffins prepared with low or high β-glucan barley flour with 100% sugar Table 13: Average L, a*, b* color values for surface color of muffins prepared with low or high β-glucan barley flour with 0% sugar Table 14: The average L, a*, b* color values for interior color of muffins prepared with low or high β-glucan barley flour with 100% sugar Table 15: The average L, a*, b* color values for interior color of muffins prepared with low or high β-glucan barley flour with 0% sugar Table 16: Average maximum peak force to compress muffins as a measure of firmness Table 17: Nutrition Facts for Muffin Formulations Table 18: The mean values of each attribute measured by the QDA panel for muffins prepared with Sustagrain flour with 100% sugar and 0% sugar, sweetened with stevia

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LIST OF ILLUSTRATIONS

Figure 1: Molecular Structure of β-(1 3)- and β-(1 4)-glucan Figure 2: Structural elements present in arabinoxylans Figure 3: Extraction and purification of β-glucans from barley and oats Figure 4: Structural Components of Stevioside, Rebaudioside A, and Steviol Figure 5: Nutrition Label for Bob’s Red Mill Ground Flaxseed Meal and Bob’s Red Mill barley flour Figure 6: Example of water separated from barley flour after centrifugation Figure 7: Apparatus and set-up of TA.XT2 Texture Analyzer for Lubricated Squeezing Flow Technique Analysis of Doughs Prepared Using Barley Flours Figure 8: Typical RVA pasting profile of a normal maize starch for viscosity and temperature as a function of time Figure 9: Water absorption indices of high and low β-glucan barley flour Figure 10: Percentage Increase in Muffin Height (Rise) After Baking Figure 11: Percentage Decrease in Muffin Weight (Moisture Loss) After Baking Figure 12: Biaxial Extensional Viscosity as a Function of Biaxial Strain Rate for Sustagrain Dough and Bob’s Red Mill Barley Flour Dough Figure 13: Pasting profile for low and high β-glucan barley flours Figure 14: Strain vs. shear rate relationship of muffin batter with varying levels of beta-glucan and sugar Figure 15: Effect of % Strain on G’ of muffin batters containing varying amounts of beta-glucan Figure 16: Effect of % Strain on G” of muffin batters containing varying amounts of beta-glucan Figure 17: Average L a*b* Values for low β-glucan and high β-glucan Barley Flour Varieties Figure 18: Visual Difference in Flour Color.

x

Figure 19: Surface color values for muffins prepared with low β-glucan Bob’s Red Mill brand barley flour Figure 20: Muffins prepared with low β-glucan Barley Flour Figure 21: Surface color values for muffins prepared with high β-glucan barley flour Figure 22: Muffins prepared with high β-glucan Barley Flour Figure 23: Interior color values for muffins prepared with low β-glucan barley flour Figure 24: Interior Surface Images of Muffins Prepared with low β-glucan barley Flour. Figure 25: Interior color values for muffins prepared with high β-glucan barley flour Figure 26: Interior Surface Images of Muffins Prepared with high β-glucan barley flour Figure 27: Typical texture profile curve for high β-glucan muffins prepared with 100% sugar and 0% sugar Figure 28: The average maximum peak force to compress muffins as a measure of firmness Figure 29: The mean values of attributes measured by the QDA panel for muffins prepared with high β-glucan barley flour with 100% sugar and 0% sugar, sweetened with stevia Figure 30: Sweet steviol glycosides from leaves of Stevia rebaudiana

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CHAPTER 1

LITERATURE REVIEW 1.0 Introduction The history of barley usage dates back to approximately 8000 B.C. and is

considered one of the oldest cultivated crops as it was a mainstay of ancient civilization

and contributed to the diet of working class people up until the end of the 19th century.

Many food products such as porridges, broths, hard biscuits, and flat breads were

prepared utilizing barley. The fermentation of the grain led to the production of various

types of alcoholic beverages, beer being one of the most well-known and second highest

consumed alcoholic beverage today following wine (Jones 2009). Although barley has

lost its place as a primary staple for modern times, mainly due to the introduction and

proliferation of the wheat industry, the health benefits and functional food uses are being

discovered and it is emerging as a major ingredient in current food formulations

(Anonymous 2005).

The concept of functional foods has been gaining much attention in the recent

times. Although there is no legislative definition of a functional food, one of the well-

accepted definition is “Food similar in appearance to conventional food that is intended

to be consumed as part of a normal diet, but has been modified to subserve physiological

roles beyond the provision of simple nutrient requirements” (Siró, Kápolna et al. 2008).

Similarly, The Institute of Medicine's Food and Nutrition Board defined functional foods

as "any food or food ingredient that may provide a health benefit beyond the traditional

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nutrients it contains" (Hasler 1998). Thus, fiber rich foods can be considered as a

functional food as it provides health benefits to the consumer.

One pressing issue in the American schools has been that of childhood obesity.

Over one-third of children ages 12 to 19 years old are overweight (Ogden, Carroll et al.

2008) and the prevalence of childhood obesity has increased three-fold from 1980 to

2000 according to Center of Disease Control Health data Division of Adolescent and

School Health (2008). The health consequences and social difficulties associated with

childhood obesity make this a tremendously problematic situation. As a result, many

institutions and individuals are involved in trying to figure out the sources and solutions

to childhood obesity. National data show that children who participate in the National

School Lunch Program (NSLP) obtain over half of their daily total food energy from

school meals. Many social programs have been established at the schools, but the main

way to target the problem is by targeting food products that are consumed by the school

children. One such way is to introduce nutritionally-sound and wholesome food products

into the school lunch programs, which are consumed by children and adolescents

everyday in the public schools. It is crucial that the product shall maintain quality

through processing, storage, preparation, and serving. Most importantly, it should

provide sensory acceptability among children so that it will be fully consumed and thus

provide the intended nutritional and health benefits.

The United States Department of Agriculture (USDA) oversees a nationwide

program called National School Lunch Program (NSLP), which provides and manages all

breakfast and lunch meals being served to students in the public school system. The goal

of the program is to provide healthy, nutritious and wholesome food products to school

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children that choose to consume meals provided at the public schools. As part of the

NSLP, the USDA sets federal nutrition requirements for the schools to follow when

creating a menu plan. The nutritional values of the meals served to students are reported

to the government as a weekly average. Federal nutrition requirements are that the meals

meet one third of the Recommended Daily Allowances (RDA) for protein, calcium, iron,

vitamin A and vitamin C as appropriate for the levels for the age group served. The

meals should also be limited to 30% calories from fat and 10% calories from saturated

fat. Along with these guidelines, the schools should also try to be consistent with the

most current Dietary Guidelines of America (2005) (USDA 2009).

One prevalent issue is the lack of consumption of fiber rich foods in children’s

diets. In a study conducted by The National Health and Nutrition Examination Survey

(NHANES), it was determined that grain based dessert products account for only 5% of

the total fiber consumption in the diets of children and adolescents between the ages 2-18

(2010). In 2002, the National Academy of Sciences released the Dietary Reference

Intakes (DRI) for macronutrients and fiber, which recommended that Americans of all

ages consume 14 g total fiber per every 1,000 kcal total energy intake, based on evidence

for reduced cardiovascular disease risk at that level. In addition, fiber protects against

constipation and has also been shown to have many other health benefits, including

decreased risk of some cancers, obesity, cardiovascular disease, and diabetes. One

striking result of this study was that the main sources of fiber in children’s diets were

foods that were relatively low in fiber density (eg, low-fiber fruits) (Sibylle, Diane et al.

2005). Thus, it is necessary to develop products with high fiber content which is aimed

4

toward the school lunch program and can contribute to the total daily fiber consumption

recommendation as given in the DRI.

1.1 Health Benefits of Barley

Historically, barley has been used in many Asian, European, and African

countries in various products such as soups, flat breads, and porridges. Although the use

of barley declined through the 19th and 20th century as wheat and rice became more

prominent in the global diet, the various health benefits of barley are being discovered

and it is now known to be an excellent source of whole grain. Thus, it is becoming an

increasingly desirable product to use in formulations (Baik and Ullrich 2008). There are

numerous health benefits of barley flour, which are predominantly attributed to the fiber

present in the commodity.

1.1.1 Fiber content of barley

Dietary fiber is a major component of whole grains, which has low energy

density, and has been shown to act as a satiating ingredient. In fact, the current

recommendation for Americans for daily fiber consumption is between 25-35 g, with a

quarter of that amount required as soluble fiber (Hecker, Meier et al. 1998). One group

of dietary fibers, particularly the soluble fibers, is usually viscous or gel-forming.

Viscous dietary fibers, present in some whole grains such as oats and barley, create

gastric distention and delay gastric emptying. Subsequently, satiety-related hormones are

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produced, which signal fullness. Thus, the consumption of whole grains containing

soluble fibers has been shown to increase satiety and thus thought to reduce overall

energy intake in a meal. Compared to other grains, barley contains a relatively high

concentration of beta-glucan, a viscous and fermentable dietary fiber, and therefore may

be highly satiating. Sustagrain barley, which contains 50% of the soluble fiber as beta-

glucan, was given to human subjects to study its effect on satiety along with oatmeal and

rice products, which contain fewer grams of fiber per serving. It was found that the

barley product, which contained the highest amount of fiber, was the most satiating as it

left subjects feeling not as hungry for the next meal when compared to meals where the

rice and oatmeal products were consumed (Schroeder, Gallaher et al. 2009).

The arabinoxylans present in barley are a source of insoluble fiber. It has been

found that enzymes present in the colon can specifically hydrolyze arabinoxylans,

resulting in arabinoxylan oligosaccharides. These oligosaccharides are said to have a

prebiotic effect, meaning that they promote the growth of beneficial bacteria in the gut.

Soluble dietary fibers play a role in the reduction of blood cholesterol and postprandial

blood glucose and insulin. Soluble arabinoxylans may possess these qualities as well

(Beaver 2008).

1.1.2 Effect of Barley on Glycemic Index and Insulin Response

The concept of glycemic index (GI) was first introduced in 1981 as a means for

identifying and classifying carbohydrate-rich foods based on their ability to raise

postprandial blood glucose levels. A lower glycemic response is desirable in both

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healthy and diabetic individuals as it prevents the spiking of blood glucose levels. In a

study done with South Asian chapati flatbreads which contained varying percentages of

barley flour mixed with wheat flour, it was hypothesized that high-molecular weight

barley β-glucan added to a food product subjected to mild cooking would be effective in

lowering postprandial glycemia. As predicted, it was found that the higher levels of β-

glucan resulted in lower serum glucose levels. The fiber may affect glycemic response

by forming a physical barrier to enzymatic hydrolysis of starch (KNUCKLES, HUDSON

et al. 1997). This suggests that the addition of high level of β-glucan containing barley

would be beneficial those individuals and populations that have a prevalence of type-2

diabetes (Thondre and Henry 2009).

In another study done with human subjects at a higher risk for insulin resistance,

they were fed varying amounts of β-glucan containing Sustagrain barley. It was found

that those who consumed 10 g of β-glucan in their diet showed significantly lower spikes

in blood glucose levels, which was measured over a two hour glucose tolerance test. This

is significant for those that are at risk for developing type-2 diabetes or have insulin

resistance, which is often seen in obese individuals and nowadays even in children.

Although a rather larger dose of the barley fiber containing food would need to be

consumed, it is a reasonable amount and shows that it could be very beneficial for

individuals who are at a higher risk for developing type 2 diabetes or have insulin

resistance (Kim, Stote et al. 2009). As this study was done in at-risk women whose

average age was 51.6, it is possible that the amount of barley β-glucan necessary for a

similar effect on children or healthy individuals with normal blood glucose and regulated

insulin levels would be much lower.

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In a similar study done with 10 men who were fed bread products as a breakfast

meal prepared with three different levels (35, 50 and 75%) of the (1→3;1→4)-β-glucan

rich barley genotype Prowashonupana, 50% common barley, or 100% white wheat, and

their postprandial blood glucose and insulin responses were measured. It was found that

for the subjects that consumed the bread prepared with 50% and 75% Prowashonupana

barley had a statistically significant reduction in glucose response levels. For bread that

was prepared with a 50% common barley composition, there was not a significant

reduction in postprandial glucose levels. This is an important indication that the higher

percentage β-glucan formulated bread had a much more beneficial effect on glucose

levels (Östman, Rossi et al. 2006). There is strong evidence from numerous studies that

high fiber, particularly from β-glucan in barley, has a beneficial effect on blood glucose

levels and thus could delay or prevent the onset of insulin resistance or diabetes.

1.1.3 Effect of Barley Fiber on Lowering Cholesterol

The fiber components of barley, particularly the soluble β-glucan have been

shown to have a cholesterol-reducing effect in a study conducted using rats as a model,

where food products such as tortilla, granola bar, and pudding with added β-glucan were

fed. The soluble fraction, which contains mostly pectin, arabinoxylan, and β-glucan, has

the ability to lower blood serum cholesterol, through its tendency to increase viscosity in

the intestine, thus affecting the bile acid-cholesterol cycle. Through this mechanism, the

cholesterol-lowering effects occur by blocking the absorption of fat in the intestines

(Hecker, Meier et al. 1998). In another study conducted using human subjects who were

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fed a barley-rich diet, the low-density lipoprotein cholesterol concentration was

significantly lower at week four in the barley group than in the standard group, who were

not fed a diet containing barley (Li, Kaneko et al.).

Coronary Heart Disease (CHD) is the cause of almost 500,000 deaths annually

and the top risk factors for CHD include high total cholesterol levels and high levels of

low density lipoprotein (LDL) cholesterol. Supporting scientific evidence shows that

adding barley to one's diet can contribute to lowering serum cholesterol. As part of its

continuing initiative to provide Americans with the information they need to make

healthy nutritional choices about foods and dietary supplements, in 2005, the Food and

Drug Administration (FDA) approved that whole grain barley and barley-containing

products are allowed to carry a claim that they reduce the risk of coronary heart disease

(CHD) under the Code of Federal Regulations (CFR 101.81). Whole barley and dry

milled barley products such as flakes, grits, flour, meal, and barley meal are all products

that can use this health claim. An example of the health claim that may be used on

products is: "Soluble fiber from foods such as [name of food], as part of a diet low in

saturated fat and cholesterol, may reduce the risk of heart disease. A serving of [name of

food] supplies [x] grams of the soluble fiber necessary per day to have this effect." To

qualify for the health claim, the barley-containing foods must provide at least 0.75 grams

of soluble fiber per serving of the food, and the health claim in CFR 101.81 is based on

the consumption of total 3 grams of beta-glucan soluble fiber daily (FDA 2005; NBFC

2006). The addition of this health claim is very important as it is strongly supported by

scientific evidence and will make consumers more aware of the health benefits of

consuming barley products.

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1.1.4 Antioxidant potential from barley

Some recent studies have focused on demonstrating and studying the antioxidant

properties and compounds found in barley. Antioxidants or phenolic structured

antioxidant compounds have been detected in barley and recent studies have shown that

cereals contain more phytochemicals than previously considered. These constituents of

barley are considered to be the most important source of antioxidants in cereals and exist

in both the free as well as bound form. The majority of the free phenolics are found as

flavanol compounds, whereas the bound phenolics are mainly phenolic acids. Both of

these groups are known to have antioxidant activity and possibly contribute health

benefits. Cereals are therefore claimed to be good sources of natural antioxidants.

Preliminary results suggest that these phenolic acids are absorbed in humans and that

their antioxidant activity may reduce the risk of coronary heart diseases, cancers, and

aging processes (Holtekjølen, Kinitz et al. 2006).

In addition to the potential health benefits associated with phytochemicals, these

phenolic compounds have important functional properties. Firstly, phytochemicals in

grains contribute to product quality in terms of color, flavor, and texture. The phenolic

acids and the flavanol polymers may be perceived as sour, bitter, and astringent.

Secondly, they also influence bread quality by interfering with the dough formation. The

changes in antioxidant properties were studied after baking bread containing barley. The

most significant change was seen among the different barley varieties, but much less after

storage or baking (Holtekjølen, Bævre et al. 2008).

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1.2 Chemical and Physical Characteristics of Barley

1.2.1 Sustagrain Barley Variety

The Sustagrain barley variety is a proprietary barley variety that was developed

by ConAgra Foods through a conventional barley breeding program at Montana State

University in the late 1970s. This particular variety is generically known as

“Prowashonupana,” which is a waxy, hulless barley variety that has a unique

macronutrient composition. The variety’s name is an acronym that represents its grain

characteristics and lineage: PRO: high protein (high lysine); WA: waxy starch; SHO:

short awned; NU: nude (hulless); and PANA: derived from the parent barley Compana.

It is much higher in fiber and protein, but lower in starch compared to many other

common cereal grains. Thus, this particular variety of barley can be used to formulate

products with desirable health benefits (Arndt 2006). Sustagrain barley is available as a

fine ground flour or and quick flakes which are tannish-brown in color (ConAgra).

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Sustagrain Barley Nutritional Data (100g Basis)

Calories 390 Vitamin A 0 IU

Calories from Fat 60g Vitamin C 0 mg

Fat 6.5g Calcium 33mg

Saturated Fat 1.8g Iron 3.6mg

Cholesterol 0g Vitamin B1 (Thiamin) 0.6mg

Carbohydrates 64.3g Vitamin B2 (Riboflavin) 0.3mg

Total Dietary Fiber 30g Vitamin B3 (Niacin) 4.6mg

Soluble Fiber 12g Potassium 452mg

Protein 18g Zinc 2.8mg

Sodium 12mg

Table 1: Nutritional Composition of Sustagrain Barley (ConAgra) 1.2.2 Chemical Composition of Sustagrain Barley (Prowashonupana)

The carbohydrate distribution in Prowashonupana barley is at least 30% dietary

fiber and less than 30% starch. This unique composition of fiber to starch is about 2-3

times the amount of fiber and about half the amount of starch compared with other

common cereal grains. Approximately half the dietary fiber, 50%, consists of β-glucan.

This particular variety also provides other whole-grain nutrients including healthy lipids,

vitamins, minerals, tocotrienols, and phytonutrients (Arndt 2006).

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Table 2: Average Nutrient Comparison for Hulless Barley, Oats, and barley variety

Prowashonupana (Prowash) Barley (Arndt 2006)

Microscopic and chemical analyses were conducted to compare the structure,

macronutrient distribution, and macronutrient content of Prowashonupana barley variety

to another type of waxy, hulless (naked) barley variety: Bz 489-30. Waxy naked barleys

have previously been reported to contain 51.7–60.5% starch, 12.6–16.6% protein, 12.6–

20.5% dietary fibre, 2.6–3.3% fat and 1.5–3.5% ash, while the content of β-glucan has

been shown to vary between 6 and 11% of dry matter. In contrast, the Prowashonupana

variety has been shown to have a lower starch content (21-31%), while the contents of the

dietary fiber, protein and fat have been shown to be high (33-36%, 18-22%, and 6%,

respectively). Furthermore, the content of β-glucan has been reported to be 2-3 times as

high as in other naked waxy barleys, varying from 15-18% of dry matter. This study

closely analyzed the association between structure and chemistry in the barley grain.

Through chemical isolation methods it was found that the cellulose and arabinoxylan

content was higher in the Prowashanupana variety of barley. It was hypothesized that the

Nutrient (%) Hulless Barley Oats Prowash

Barley

Protein 13 15 20

Fat 3 6 7

Starch 60 59 21-30

Total Dietary Fiber 13 10 30

β-Glucan 5 5 15

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thicker cell wall indicates a high content of β-glucan while a large amount of starch

granules is associated with higher starch content. Fluorescence microscopy was used to

study the structural characteristics of the grains and it was observed that the

Prowashonupana barley variety had irregular endosperm cells with thicker cell walls, and

thus the higher β-glucan content is unique to the Prowashonupana variety of barley

(Andersson, Andersson et al. 1999). These studies comparing different varieties of

barley with the Prowashonupana (Sustagrain) barley variety show that there is a definite

advantage to use the latter in product formulations that are geared towards providing a

nutritional and functional advantage.

1.3 β-Glucans and Arabinoxylans

Arabinoxylans and mixed linkage (1→3)(1→4)- β -D-glucans, commonly

referred to as beta-glucans, are the major non-starch polysaccharides present in various

tissues of barley. Depending on the genotypic or cellular origin, both polymers exhibit

variations in their molecular structures. The molecular features of β-glucans and

arabinoxylans are important in determining their physical properties, such as water

solubility, viscosity, and gelation properties as well as of their physiological functions in

the gastro-intestinal tract, which most notably provides the health benefits mentioned

previously. The potential application of β-glucans as food hydrocolloids has been also

proposed based on their rheological characteristics. In addition to enhancing solution

viscosity, β-glucans have been shown to gel under certain conditions. Arabinoxylans

have been shown to significantly affect cereal based processes such as milling, brewing,

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and breadmaking. Furthermore, arabinoxylans offer nutritional benefits of soluble and

insoluble fiber, and because of the presence of phenolic moieties in their molecular

structures, they may also have some antioxidant properties (Izydorczyk and Dexter

2008).

β-Glucan is a trivial name for the glucose polymer found in the endosperm cell

walls of barley and oats. The β-bond is not digestible by enzymes in human

gastrointestinal tract, resulting in the classification of β-glucan as a soluble dietary fiber

(Burkus and Temelli 2005). β-glucans consist of linear unbranched polysaccharides of

linked β-(1 3)- and β-(1 4)-D-glucopyranose units in a non-repeating but non-

random order, as seen below:

Figure 1: Molecular Structure of β-(1 3)- and β-(1 4)-glucan (Chaplin 2009)

β-glucans form 'worm'-like cylindrical molecules containing up to about 250,000

glucose residues that may produce cross-links between regular areas containing

consecutive cellotriose units. They form thermoreversible infinite network gels. 90% of

the β-(1 4)- links are in cellotriosyl and cellotetraosyl units joined by single β-(1 3)-

links with no single β-(1 4) or double β-(1 3)-links. The main use of β-glucans is in

texturizing by functioning as a fat substitute, which is made possible by the increase in

15

viscosity. One such product, Nutrim, is prepared by subjecting an aqueous suspension of

barley flour to a high temperature mechanical shearing in the presence of thermostable α-

amylase, followed by centrifugations and drying of the supernatant. In addition to β-

glucans (5–15%, depending on the β-glucan content in barley used for extraction), a

Nutrim preparation contains also starch, amylodextrin, and proteins and has been used to

make low fat cheddar cheese (Izydorczyk and Dexter 2008). In a study done using a β-

glucan fat substitute product called Trimchoice, it was found that a 35% substitution with

fat resulted in shortbread cookies that were comparable in terms of texture, color, and

taste with the full-fat control (Sanchez, Klopfenstein et al. 1995). High molecular weight

β-glucans are viscous due to labile cooperative associations whereas lower molecular

weight β-glucans can form soft gels as the chains are easier to rearrange to maximize

linkages. Barley β-glucan is highly viscous and pseudoplastic, both properties decreasing

with increasing temperature. Although these properties cause difficulty in the brewing

industry by negatively affecting fermentation and filtration, β-glucans have important

functionality in foods as well as physiologically (Chaplin 2009).

Arabinoxylans are non-starch polysaccharides found in the cell walls of plants.

They are generally classified as hemicelluloses, or more specifically pentosans, a series

of 5 carbon sugars. Their general structure is comprised of β-(1,4) linked D-

xylopyranosyl backbone with α-L-arabinofuranose units attached as side residues via α-

(1,3) and/or α-(1,2) linkages (Beaver 2008). They are present in Prowashonupana barley

at 12% dry weight basis (Andersson, Andersson et al. 1999)

16

Figure 2: Structural elements present in arabinoxylans (Izydorczyk and Dexter 2008)

The arabinoxylan structure affects its physiochemical properties. Arabinoxylans

have the ability to bind water which may alter the dough rheology, processing and

finished product attributes of many baked products. The high water holding capacity of

arabinoxylans delays starch gelatinization most likely by restricting the amount of water

available for starch gelatinization. The arabinoxylans also protect the starch from α-

amylase enzymatic degradation which results in increased bread volume, better crumb

elasticity and increased shelf life (Beaver 2008).

17

1.4 Properties and Molecular Interactions among Major Food Components

Along with the many physiological benefits of barley β-glucans, these compounds

exhibit certain rheological and physical properties in the food matrix that make it a

suitable for various food applications. Such beneficial health effects have been attributed

to the solubility of β-glucans in water and their capacity to form highly viscous solutions.

Cereal β-glucans exhibit considerable diversity in their structures, including the ratio of

tri- to tetramers, the amount of longer cellulosic oligomers and the ratio of β-(1-4):β-(1-3)

linkages. These structural features appear to be important determinants of their physical

properties, such as water solubility, viscosity, and gelation. The potential use of β-

glucans as hydrocolloids in the food industry is based mainly on their rheological

characteristics, i.e. their gelling capacity and ability to increase the viscosity of aqueous

solutions. Thus, β-glucans can be utilized as thickening agents to modify the texture and

appearance of food formulations or may be used as fat mimetics in the development of

calorie-reduced foods. β-Glucan-rich fractions from cereals or purified β-glucans have in

fact been successfully incorporated into products such as breakfast cereals, pasta, noodles

and baked goods (bread, muffins), as well as dairy and meat products (Lazaridou and

Biliaderis 2007).

1.5 Beta-glucan extraction

Extraction of β-glucans can be done to verify the amount present in the barley

varieties. Subsequently, the properties of β-glucans alone can be studied to model how

18

they behave when subjected to thermal, chemical, and physical changes. Extraction and

isolation of pure β-glucans from oat and barley are conducted using the procedure

outlined in Figure 3. Pure β-glucan has been added to several baked products with

successful applications (Thondre and Henry 2009). It is to be noted that this procedure is

widely accepted and used to confirm the amount of β-glucans present in a commodity.

Figure 3: Extraction and purification of β-glucans from barley and oats (Biliaderis and

Izydorczyk 2007).

19

1.6 Water absorption capacity and effect on end-products

The addition of β-glucans to wheat flour used for bread-baking barley has been

shown to result in a higher water absorption capacity. The addition of β-glucans to a

dough formulation also increases the development time, the stability, the resistance to

deformation and the extensibility of poor breadmaking quality doughs, as well as the

specific volumes of the respective breads, exceeding even that of the good breadmaking

cultivar. Traditionally, barley has not been used in bakery products because it lacks

substantial gluten proteins and the end-products have poor sensory qualities (Bhatty,

1999). Furthermore, studies showed that addition of fibrous materials to wheat flour

weakens the crumb cell structure, due to the dilution and weakening of the wheat gluten

protein network. Similarly, Dubois (1978) emphasized that especially utilization of the

water-insoluble fractions impair the gas retention of the dough and thereby change the

texture and appearance of the baked product. More recent studies have demonstrated that

β-glucan-enriched barley fractions, blended with wheat flour, can produce bread with

acceptable sensory properties (Skendi, Biliaderis et al. 2010).

In a study done by Sharma and Gujral (2010), where several barley varieties were

used to determine differences in their water absorption, water solubility index, and oil

holding capacity, it was found that there was some difference among the different

varieties of barley. It was determined that the water solubility index ranged from 9.23%

to 11.77% in different cultivars. DWR-28 and RD-2552 varieties had highest and lowest

water solubility index respectively, however only DWR-28 showed significant difference

in water solubility index as compared to all other cultivars. The oil holding capacity

20

significantly varied among the cultivars and ranged from 1.5 to 1.68 g/g, DWR-28 and

RD-2052 had highest and lowest oil holding capacity among the cultivars. Water

absorption capacity ranged from 1.38 to 1.63 g/g, the highest exhibited by PL-172 and

RD-2052 and lowest exhibited by RD- 2503. Bhatty (1993) reported similar value for

water holding capacity and oil absorption capacity for barley flour. The water absorption

capacity could be attributed to β-glucan content in barley flour because there was positive

correlation (R = 0.843) between β-glucan content and its water absorption capacity.

It is known that the flow behavior and gelling properties of β-glucans can largely

vary with the concentration and the molecular size of the polysaccharide concentration.

Thus, understanding the effects of barley β-glucans with different molecular weights on

the rheological properties of wheat flour doughs with different breadmaking quality is

essential for determining both the dough handling properties during processing and the

quality of the end products. In a recent paper published by (Skendi, Papageorgiou et al.

2009), the effect of adding low (105 Da) or high (2.03 x 105 Da) molecular weight barley

β-glucans in two wheat flours of different breadmaking quality were studied. Mechanical

spectra and creep-recovery analysis data within (low stress) and out (high stress) of the

linear viscoelastic region were obtained and revealed that the rheological behavior of β-

glucan-enriched doughs depend on concentration and molecular weight of the

polysaccharide as well as on the flour type used. Addition of β-glucan increased the G’

values of the good breadmaking quality flour doughs, whereas decreased the G’ of the

poor quality wheat cultivar. Supplementation with β-glucans increased the resistance to

deformation, flowability and elasticity of the doughs under low stress. Significant

correlations between frequency sweep and creep–recovery parameters of optimally

21

developed doughs from both flours were found. The addition of β-glucan in the dough

recipe of the poor breadmaking wheat flour may result in similar rheological responses to

those obtained from non-fortified good breadmaking quality wheat flour.

Many authors have reported that due to the β-glucans ability to absorb high

quantities of water, doughs fortified with β-glucans display a significant increase in the

farinograph water absorption values. It is generally recognized that water plays the most

important role on the viscoelastic properties of the dough during mixing; i.e. the

distribution of the dough materials, their hydration, and the gluten protein network

development strongly depend on the quantity of added water (Skendi, Papageorgiou et al.

2010). Small deformation dynamic rheological tests and creep-recovery measurements

are often employed for dough characterization and the derived rheological data are

explored as predictors of breadmaking performance.

1.7 Rheological Properties Influenced by barley flour beta-glucan content

Rheology is concerned with how all materials respond to applied forces and

deformations. Basic concepts of stress (force per area) and strain (deformation per

length) are key to all rheological evaluations (Tabilo-Munizaga and Barbosa-Cánovas

2005). Shear-thinning behavior in foods may be conceptualized by the breakdown of

structural units in a food due to the hydrodynamic forces generated during shear. Most

non-Newtonian foods exhibit shear-thinning behavior, including many salad dressings

and some concentrated fruit juices. In fact, most foods fall into this non-Newtonian

category (Rao 1999). Beta-glucans are one such material that have been shown to exhibit

22

such behavior and have demonstrated viscoelastic properties (Papageorgiou, Lakhdara et

al. 2005). Data reported on the consistency and viscoelastic properties of batter are

important in the development of new products (Kalinga and Mishra 2009).

Characterizing the mechanical behavior of food materials is complicated by the

fact that many food materials are viscoelastic, so their mechanical properties lie between

that of a purely elastic solid and that of a viscous liquid. Using oscillatory rheology, it is

possible to quantify both the viscous-like and the elastic-like properties of a material at

different time scales; it is thus a valuable tool for understanding the structural and

dynamic properties of food systems (Wyss, Larsen et al. 2007).

1.8 Stevia as a Sweetening Agent in Consumer Products

Stevia is a generic name for the sweetness-providing compounds, particularly the

steviol glycosides, extracted from the herb Stevia rebaudiana (Bertoni). It is generally

available as a mixture of steviol compounds, with the predominant sweetness compound

being Rebaudioside A (Carakostas, Curry et al. 2008). Stevia has negligible caloric value

for use in food products and beverages since it is used at a very low concentration. Stevia

leaf extracts exhibit a sweetening level of 15-30 times sweeter than sucrose, dependent on

the extract quality and raw material (SM Savita 2004). In 2008, stevia gained approval

for mainstream food usage from a dietary supplement status. Therefore, products

containing stevia launched thereafter, and have been gaining popularity among food

manufacturers because of its natural label and low-calorie benefits (Lord and Sant'Angelo

2010). Although stevia has been gaining acceptance and has increasing use in the food

industry in the past few years, there are technical issues with the product due to the

23

presence of bitter compounds that are also incorporated into the sweetener during the

extraction process. There is also a lingering licorice aftertaste and sweetness at a higher

use concentration, which has been the cause for the limited acceptance of the product.

However, there are benefits of using stevia extracts, especially in baked products

where thermal processing occurs. Rebaudioside A has been shown to have thermal

stability in two specific studies. One was the use in pasteurized dairy product and the

other was in a laboratory baking study with temperatures up to 390° F. Due to its thermal

stability, stevia is suitable for baking applications. However, stevia is not the perfect

substitute for sugar in bakery applications. The sole function of stevia would be in

providing sweetness. Stevia lacks the ability to add texture, caramelize, feed the

fermentation of yeast or help tenderize a batter, all properties that sugar possesses. Also,

cakes made with stevia may not rise as well, and achieving a soft, chewy cookie may

require additional ingredients (Jones 2006).

Figure 4: Structural Components of Stevioside, Rebaudioside A, and Steviol

(Carakostas, Curry et al. 2008)

24

1.9 Conclusions from Literature Review and Objectives for Research

Appealing to the heightened awareness of health issues such as childhood obesity,

prevalence of diabetes, and lack of fiber in the diet, more nutritious products need to be

made available to school children. As manufacturers make the changes to their products

to improve the nutritional value, the food quality should not diminish. Thus far, barley

flour has limited approaches in modern-day food products despite its known health

benefits. This may be attributed to the presence of a bitter taste and a strong whole-grain

character as well as the requirement of high sugar content in baked products to mask this

taste. However, the addition of sugar increases the caloric value of the product. To

address this issue, a natural sweetener called stevia will be studied by incorporating it

into a model baked product prepared with barley flour. The essential food quality

properties of color, taste, texture, and nutritional value will be used to assess the food

characterization of a barley flour containing product.

The specific objectives in this research include identifying key parameters

responsible for processing and to monitor the effect of water absorption with varying

levels of β-glucans in barley flour, specifically noting how this difference affects some of

the rheological properties. Another aim is to reduce sugar levels in the product by

incorporating a natural sweetener called Stevia and to monitor its influence through

instrumental and sensory analysis. Finally, the instrumental findings of the research will

be compared with the sensory aspects of the model baked product to determine whether

there exists a detectable difference though a human response.

25

CHAPTER TWO

Materials and Methods

A muffin type of baked product will be used as a model to assess the color,

texture, and sensory properties as an effect of the β-glucan content and reduced sugar

levels on the final product. Most importantly, the interactions among the primary

components of the product need to be well-understood. Thus a model system of barley

flour, natural sweetener, water, and other minor components will be used to study the key

processing effects through instrumental and sensory analyses. The aim is to incorporate a

natural sweetener while keeping the low-calorie and low glycemic index aim in focus. At

the same time, the functional changes occurring due to the reduction in sugar levels and

increased beta-glucan content will also be monitored.

Similarly, the type of fat used in the product formulation is intended to provide

some health benefit to the consumer in addition to its role in the baked product

formulation. Thus, flaxseed meal will be added to the product as it provides a source of

beneficial omega-3 fatty acids and adds fiber. In a study done by (Fiscus, Harris et al.

1999), it was found that flaxseed substituted into whole wheat flour at 25% and 50%

levels showed similar sensory results to the control which used 100% wheat flour in the

preparation of peanut butter cookies and banana bread. Important food quality

characteristics such as flavor, texture, and mouthfeel were found to have no significant

difference between that of the control and the formulation with the flaxseed added.

Minor ingredients such as flavorings and leavening agents will present in the final

product, but not studied in depth in the analytical parts of the project. The main objective

26

is to determine and examine the behavioral differences among the different barley flours,

considering Sustagrain barley flour as the high β-glucan and a commercially available

brand of barley flour as the low β-glucan counterpart.

2.1 Ingredients Used in Baking Procedures and Analytical Measurements

Two varieties of barley flour will be used to study the functional changes caused

by the varying amounts of beta-glucan present in the two brands of barley flour. One is

barley flour manufactured by Bob’s Red Mill, a commercially available brand, which will

be considered as the low beta-glucan barley flour. The other is Sustagrain, which as

previously mentioned, is a high beta-glucan (15%) containing barley flour sold under the

ConAgra Mills brand. The main objective is to identify the key behavioral differences

with other food components and compare how the beta-glucan levels affect the water

absorption capacity, rheological properties of the batter, textural properties in a model

baked product, and the final product color.

Ground flaxseed meal supplied by the company Bob’s Red Mill will be used in

the muffin formulations to obtain color and textural measurements. The company

website states the following on the product page, “In a 2 Tablespoon serving size (13

grams) the fiber content is 1.33 grams of Soluble Fiber and 2.67 grams of Insoluble Fiber.

Ground Flaxseeds are a good source of Omega 3 Fatty Acids. In a 2 Tablespoon serving,

there is 2400 mg of Omega 3 (2010).”

27

Figure 5: Nutrition Label for Bob’s Red Mill Ground Flaxseed Meal (left) and Bob’s Red

Mill barley flour

2.2 Water Absorption Index of Low and High β-glucan Barley Flours

The amount of water used for a baked product has a great effect on the outcome

of the final volume and texture (Osorio, Gahona et al. 2003). Therefore, it is necessary to

determine how much water would be absorbed into the flour prior to developing product

formulations. The water absorption index can be determined by simple methods using

barley flour and water. Water absorption capacity of flour was measured by the ratios

28

f

wf

mmmWAI

+=

and centrifugation methods (Sharma and Gujral 2010) (Ding, Ainsworth et al. 2006).

0.12 g Sustagrain barley flour and Bob’s Red Mill Barley flour were dispersed in 1 mL of

distilled water and placed in pre-weighed centrifuge tubes. The dispersion was stirred

using a stir-plate for 10 min followed by centrifugation for 25 minutes at 3000 rpm. The

supernatant was drained off by allowing the tubes to stand inverted for 10 minutes. The

water absorption index was calculated by dividing the weight of the flour and water

mixture obtained after draining off the supernatant by the original weight of the flour.

The averages of triplicate measurements are recorded. It was predicted that the higher β-

glucan Sustagrain flour will have a higher water absorption index since increasing

amounts of β-glucans have been shown to absorb more water (Sudha, Vetrimani et al.

2007).

Water absorption index was calculated by:

where mf = mass flour and mw= mass water.

Figure 6: Example of water separated from barley flour after centrifugation

29

2.3 Microbakery Model Formulations for Barley Muffins

A dessert type baked muffin product was used as a model to characterize the

instrumental changes occurring in the system as a result of β-glucan levels in the barley

flour as well as study the changes occurring due to the removal of sugar from the

formulation. Muffins were prepared using the following formulations, with process

variations occurring in the type of barley flour utilized (high or low β-glucan) and the

reduction in sugar levels, while using stevia to maintain sweetness levels. The recipe

ingredients were adapted from (Idzorek 2010) and modified based on preliminary baking

experiments and the quantities were reformulated and adjusted to accommodate small-

scale baking experiments. Ingredients such as eggs, banana, sugar, baking soda, vanilla

extract, and salt were sourced from local supermarkets. Banana puree was used since

fruit purees demonstrate humectant properties, promote tenderness and retain moistness,

increase shelf life, and can replace some of the sugar and/or fat in muffins and cakes (Hui

2006). The banana puree would also be helpful in providing some of the necessary

moisture to hydrate the barley flour in the formulation. Stevia leaves extract was

obtained from Spectrum Chemical.

Each set of muffins were prepared with the use of 1) Bob’s Red Mill Barley

Flour as the low β-glucan type or 2) Sustagrain Barley Flour as the high β-glucan flour.

Each formulation was prepared with the same ingredients, with the process variation

occurring in the sugar:stevia use levels, as well as the addition of ground flaxseed meal in

the 0% sugar formulations. Stevia has been shown to have a potency level perceived as

200-300 times sweeter than sucrose (1.0). However, the sweetness potency, or the

sweetness perception, in a product is highly dependent on the sucrose equivalency level.

30

The stevia to sugar equivalency use level has been reported as 4-8%, with 6% level being

a reasonable average value (Prakash, DuBois et al. 2008). Initially, stevia sweetener

levels in the product formulations were based on the previously mentioned levels. Thus,

the amount of sucrose (9.88 grams) used in the full sugar control product required 0.59

grams of stevia (6.0%) to have a similar sweetness equivalency.

Preliminary baking experiments were done to test this level of sweetness using

stevia in the formulation and it was found to be too high of a sweetness level, which also

resulted in a strong bitter aftertaste. Stevia use level was thus reduced to 0.15 grams in

the formulations, or approximately 0.24% of the total formulation. This stevia use level

was employed for baking done for instrumental measurements as well as preparation of

samples used in sensory panels.

Table 3: Formulations for Muffin Batters Used to Prepare a Model Baked Product

Ingredient (g) 100% Sugar

0% Sugar

0% Sugar + Flaxseed Meal

Barley Flour 16.5 16.5 16.5

Salt 0.05 0.05 0.05

Baking Soda 0.44 0.44 0.44

Vegetable Oil 5 5 5

Water 105° F 10 10 10

Banana Puree 25 25 25

Eggs 5.5 5.5 5.5

Sugar 9.88 0 0

Vanilla 0.3 0.3 0.3

Flaxseed Meal 0 0 2.25

Stevia 0 0.15 0.15

Total 72.67 62.94 65.19

31

Although the total weight of the batter formulations differs, the process control

was applied by weighing out muffin batters equally into mini-muffin tins. Equal amounts

of batter were utilized in all baking processes for instrumental experiments and sensory

analysis.

Procedure for preparing muffins:

A Frigidaire Gallery consumer electric convection oven was used for the baking

experiments. The oven was preheated to 325°F and the temperature was maintained

throughout the preparation of the batter and baking process. A ripe banana was pureed in

a food processor (Hamilton Beach) until it reached a smooth consistency and did not

contain any visible chunks. In a mixing bowl, the dry ingredients consisting of barley

flour, salt, flaxseed meal and baking soda were combined and set aside. In another

separate mixing bowl, oil, eggs, vegetable oil, and sweeteners were mixed and beaten

with a hand-held electric mixer (Sears) on speed 3 until thoroughly blended, for

approximately 15 seconds. Then the banana puree, vanilla, water and dry ingredients

were added to the mixture and beat with the mixer on speed 2 for 15 additional seconds

until all ingredients are blended and uniform in appearance. The batter was then weighed

out to 12 ± 1 grams in a paper muffin mold placed into a mini-muffin pan and baked for

ten minutes. The pan was then rotated 180° and baked an additional two minutes.

Muffins were then removed from the oven and allowed to cool in the pan at room

temperature for two minutes. Then, the muffins were transferred to a cooling rack for an

additional 30 minutes at room temperature. Muffins were stored in a sealed plastic zip-

top bag at room temperature (25°C) for further analysis. Texture, color measurements,

and photographs of the surface and interior were obtained within 12 hours of preparation.

32

2.4 Rise and Moisture Loss of Muffins

The variation for this experiment included the use of high and low β-glucan

barley flours in the model baked product as well as the complete removal of sugar. When

sugar was omitted from the formulation, stevia was used to maintain sweetness levels.

The heights of the muffins were evaluated by obtaining the height of the batter prior to

baking and calculating the percentage of rise, or increase in height, after muffins were

prepared. A toothpick was inserted into the center of the batter and the toothpick was

marked at the level of the batter. The toothpick was then removed. The initial height of

the batter was recorded by measuring the distance between the mark made on the

toothpick to the end of the toothpick with a ruler, in centimeters. Final heights were

obtained in the same manner after allowing the muffins to be cooled for 30 minutes. The

percentage rise, or increase in muffin height, was calculated by:

% increase in muffin height = hf – hi x 100%, hi where hf is the final height and hi is the initial height of the muffins. The initial weight, 12 ± 1 grams, of the muffin batter was recorded by placing the

batter in mini-muffin tin foil cups and weighing them on a scale. After baking, the

muffins were allowed to cool for 30 minutes and final weights were recorded. The

percentage change in weight, considered as moisture loss, was calculated by:

% decrease in muffin weight = mi – mf x 100%, mi where mf is the final mass and mi is the initial mass of the muffins.

33

Average values of four replicates are reported for both the muffin rise and moisture loss

measurements.

2.5 Rheological properties of barley dough using lubricating squeezing flow

technique

The rheological properties of a dough are a great indicator of their behavior

during baking and determining the final product texture, rise, spread, and overall quality.

Cookie spread rate is governed by dough viscosity as doughs with lower viscosity had a

higher spread rate compared to doughs with a higher viscosity (HadiNezhad and Butler

2009).

Traditional determinations of rheological properties of wheat flour dough have

been carried out using tests and instruments such as the farinograph and alveograph,

which provide important information on rheological characteristics for the development

of baking products. However, it has been seen that these tests do not allow detecting

differences of composition of the flour and addition of ingredients, nor do they provide

detailed information on physical and characteristic properties of flow behavior (Osorio,

Gahona et al. 2003). Thus, a technique called lubricated squeezing flow viscometry has

been used to quantify changes in the behavior of doughs and can be used with high

viscosity materials. This technique can detect differences among the samples that cannot

be observed under shear conditions. It also solves two major problems that occur in food

viscometry: 1) the slip condition in the surface and 2) the inadvertent rupture of the

structure of the sample when introducing it in the reduced space of the conventional

34

rheometer. This technique has been previously applied to several high viscosity products

such as peanut butter, cheese, cooked cornmeal dough, mayonnaise, tomato paste, tortilla

dough, wheat dough, yogurt, dulce de leche (milk sweet), refried beans paste and

mustard. The lubricated squeezing flow viscometry technique is one of the basic types of

biaxial extensional flow, which is the type of flow behavior that occurs during the baking

process.

Both low and high β-glucan barley dough were subjected to this type of

compression analysis to look at the flow properties of the doughs and how they affect the

final product texture. Dough samples were prepared using the previously determined

water absorption index values. Water was added to the barley flours and mixed

continuously for 3 minutes to allow the formation of a cohesive textured dough (Sudha,

Vetrimani et al. 2007). A TA.XT2 Texture Analyzer was used for the lubricated

squeezing flow technique. The TA-4, 38 mm cylinder probe was attached to a 25 kg load

cell. The platform as well as the surface of the probe were well lubricated with

commercially available food grade, edible vegetable oil to minimize any effects of

friction (Osorio, Gahona et al. 2003) and (Stojceska, Butler et al. 2007). Pre-test and

post-test speeds were set at 1.0 mm/sec and the test speed, or deformation rate, or

crosshead velocity, was set to 0.1 mm/sec. Dough discs measuring 1 cm in height and 2

cm radius were formed and placed on the platform. They were allowed to rest for 5

minutes prior to testing in order to stabilize internal tensions. The dough was compressed

to 60% of its original height, or 6.0 mm. The force, time, and distance parameters were

recorded automatically through the Texture Expert software. Samples were prepared and

run in triplicates with average values used for calculations of biaxial stress, biaxial strain,

35

and biaxial viscosities. Calculations to obtain biaxial viscosity vs. biaxial strain rate

curves were obtained following detailed methodology in (Osorio, Gahona et al. 2003).

Apparent biaxial extensional viscosity (ABEV) was calculated by the following formula:

ABEV = 2Ftht/ΠR2v

where Ft is the compression force (N) at time of t; ht is the height of the dough sample

(m) at time t; R is the initial radius (m) of the dough sample; v is the crosshead speed

(m/s). Data points were obtained at each second time interval and plotted to obtain a

curve of the biaxial extensional viscosity versus biaxial strain rate.

Figure 7: Apparatus and set-up of TA.XT2 Texture Analyzer for Lubricated Squeezing

Flow Technique Analysis of Doughs Prepared Using Barley Flours

36

2.6 Pasting Properties of High ββββ-glucan and low ββββ-glucan barley flours

Rheological properties of starch pasting are traditionally studied by an instrument

called the Rapid Visco Analyzer. The working principle of this type of equipment is that

the rheology is directly related to the microstructure of starch and is influenced by many

factors such as the amylose/amylopectin ratio, the chain length of amylose and

amylopectin molecules, the concentration of starch, shear and strain, and temperature.

The sample is heated over a range of temperatures and the viscosity is recorded over a

period of time. Starch granules are generally insoluble in water below 50°C, so the

viscosity of the starch mixture is low below this temperature. When the starch granules

are heated, the granules absorb a large amount of water and swell to many times of their

original size.

As the instrument generates shear conditions, the viscosity increases when the

swollen starch granules squeeze past each other. The temperature at which the rise in

viscosity is seen is known as the pasting temperature, which indicates the minimum

temperature required to cook a sample. As a sufficient amount of starch granules are

heated, there is period of time where there is a rapid increase in viscosity as the

temperature increases. The peak viscosity occurs at the equilibrium point where starch

granules are completely swollen and just as they begin the retrogradation process. The

peak viscosity and temperature indicates the water binding capacity of the starch. As the

temperature is held constant over a period of time, the starch granules begin to rupture

and polymer realignment occurs, which is evident by the decrease in apparent viscosity of

the paste and is known as the breakdown viscosity, which occurs at the beginning of the

37

cooling phase. The viscosity at this stage of heating also gives an indication of paste

stability. As the sample is cooled down back to the starting temperature, re-association

between the starch molecules, especially amylose, occurs to varying degrees, which

results in an increase in viscosity once again as a gel begins to form. This phase of the

pasting curve is referred to as the setback region, and occurs due to the retrogradation of

the starch molecules. The final viscosity gives an indication of the stability of the cooled,

cooked paste under low shear conditions (Cui and Liu 2005) and (Brabender 2005).

Below is a typical pasting curve used to illustrate the specific points in the pasting profile

determined during the duration of the run.

Figure 8: Typical RVA pasting profile of a normal maize starch for viscosity ( - ) and

temperature (---) as a function of time (Cui and Liu 2005)

38

The pasting properties of high and low β-glucan barley flours were studied using

a rheometer and a controlled temperature circulating water bath to emulate the Rapid

Visco Analyzer instrument. A Brookfield Digital Rheometer Model DV-III was used in

conjunction with a with a K10 model water bath circulator system controlled by a

Thermo Scientific Haake DC30 temperature control system, with an accuracy of ± 0.1°C.

The pasting properties of the low and high β-glucan barley flours was studied, as well as

with the addition of sugar with the same ratio to that in the muffin formulation. The

sample was prepared as a 5% wt/wt basis of barley flour in water suspension. Sugar was

present in the muffin formulations at 13.6% of the total formulation, therefore of sugar

was added was added to the 5% barley flour and water suspension at the same ratio. All

samples were mixed prior to transferring into the rheometer holding cell and allowed to

equilibrate for 3 minutes to reach an initial temperature of 50°C. The shear rate was set

to 200 rpm or 68 1/s for the duration of the run and an SC4-31 spindle was used based on

manufacturers given maximum viscosity parameters. The temperature profile was set to

begin at 50° C, then increase to 95° C, hold at 95° C for 5 minutes, and then cool to 50° C

(Stojceska, Butler et al. 2007; Sharma and Gujral 2010; Sharma, Gujral et al. 2010; Sai

Manohar, Urmila Devi et al. 2011). Time (min), temperature (°C), and viscosity (mPas)

were recorded by the Rheocalc Version 3.2 software. Peak viscosity (mPa s), breakdown

viscosity (mPa s), final viscosity (mPa s), setback viscosity (mPa s), peak time (minutes),

and pasting temperature (°C) were obtained from the graph plotted through the duration

of the sample run. Averages of triplicate values are reported.

39

2.7 Dynamic Rheological Properties of Muffin Batters

An oscillating rheometer was used to directly study the rheological properties of

batters to characterize the behavior of β-glucan concentration on the rheological

properties of the batter and resulting changes occurring during processing.

Apparent Viscosity

Muffin batters were prepared according to the same formulations used in baking

experiments and were run through a Rheometric Scientific ARES Rheometer to measure

the viscosity between strain rate of 1 to 398 s-1. The sample was loaded between two

parallel plate geometry probes and the gap was adjusted to 1.0 mm. All measurements

were made at 25°C using 25 mm diameter parallel plates. Stress and strain rates were

recorded and plotted to obtain a stress vs. strain rate curve to fit a Power-law model to

obtain the flow behavior index (K) and the consistency index (n) from the slope of the

line. The flow behavior was described by power law model, where shear stress (Pa) was

related to the shear rate (1/s) and the consistency coefficient (K in Pasn), and flow

behavior index (n) were obtained by linear regression.

Dynamic Oscillating Rheology

Oscillatory rheology is a standard experimental tool for studying behavior of

foods which exhibit viscoelastic properties, essentially those foods that are between

solids and liquids in their behavior (Wyss, Larsen et al. 2007). A Rheometric Scientific

ARES Rheometer was used to determine the oscillating rheology properties of the muffin

40

batter. Initial experiments using barley flour solutions, based on approximate moisture

content in the muffin batter, were used to determine the frequency parameters at which

muffin batter samples would be tested. The frequency chosen for the duration of the

measurements was 20 s-1. The dynamic oscillatory-shear storage and loss moduli (G′ and

G″) were measured and recorded as a function of % strain between 1 to 100%. All

measurements were made at 25°C using 25 mm diameter parallel plate geometry with a

1.0 mm gap between the plates. Values reported are based on an average of 3 replicates.

2.8 Assessing Muffin Firmness Using a Texture Analyzer

As a measurement of food quality, texture is important for observing both

defective and acceptable food products. Texture can be defined as a group of physical

characteristics that arise from the structural elements of the food and are sensed primarily

by the feeling of touch, are related to the deformation, disintegration and flow of the food

when a force is applied (Taub and Singh 1998). A group of properties based on physical

structure, sense of touch, and functions of mass, distance, and time compose the

definition of texture (Bourne 2002). The classifications of this testing are puncture,

compression-extrusion, cutting-shear, compression, tensile, torsion, bending and

snapping and deformation. A comprehensive definition of food texture analysis and

methods for evaluation can be found at Bourne (2002), (Rosenthal 1999), and Texture

Technologies (2009).

The various methods for food texture analysis depend on the properties of the

food. A common texture instrument or universal testing machine measures force as a

41

function of time and distance. A simple test of measuring the force to push a probe into a

food surface is used to measure texture known as a puncture test. The force to deform the

sample is similar to the way molar teeth bite and chew. However, the puncture test

assumes a semi-infinite geometry because of the small surface area measured. A

compression test will measure the larger surface area of the food sample by forcing it to

flow or fracture and deform dependent on its composition. This type of a compression

test is widely used in the industry as a measure of food quality during shelf-life studies

and to observe changes occurring due to ingredient modifications. When the direction of

the force applied to the sample is parallel to the direction it is sliding this is known as

shear. A food product can also be measured for the force to be divided into two sections,

bent or pulled apart (Tabilo-Munizaga and Barbosa-Cánovas 2005). Using any test, the

most accurate data depends on a consistent sample temperature, size, shape, speed,

distance and direction.

Instrumental techniques do not completely indicate textural quality of a product

since they lack the uniqueness of consumers’ perception. A sensory texture analysis is

needed to measure the quality of a food dependent on its acceptability. However, human

experience of a trained expert can be compared to physical properties results for insight

on the reaction of texture differences. Using the human senses to manipulate the food

product by eating allows for many different variables to be identified. For example, in

study of apple firmness a difference of five Newtons using instrumentation is detectable

by human perception (Harker, Gunson et al. 2006). The process of eating can measure

the actions of biting, chewing, swallowing, etc. and determine which sensations are

42

perceived at any given point. Since texture has a high affect on liking of the product, the

quality of a food can depend on the description of its meeting chosen standards.

Muffins that were prepared using the previously described formulations with low

and high β-glucan flour with varying amounts of sugar:stevia ratios and the addition of

flaxseed meal were evaluated using the TA.XT2 Texture Analyzer. A compression test

was conducted on all the muffin varieties to determine the firmness and how it is affected

by each variation in the muffins and between the two types of flours. A TA-11, 1-inch

diameter cylinder was used with a pre-test, test, and post-test speed of 2.0 mm/sec.

Muffin samples placed on the testing platform and were compressed to 10 mm of their

original height. An output of peak force (g) vs. time was obtained for each variety of

muffin in triplicate measurements, with average values reported (Texture Technologies,

Corp.). Differences between averages were determined by comparing muffin treatments

according to a t-test with a significance level of 5% (p = 0.05) using the Microsoft Excel

2003 Data Analysis ToolPak.

2.9 Evaluation of Colors Using a Colorimeter

Surface color is one of the important characteristics of baked products and is

considered as a critical index for judging baking quality. Baked products develop color

in the later stages of baking, simultaneously with crust formation and occur through

chemical processes including the Maillard reaction and sugar caramelization. The

Maillard reaction is responsible for color development at surface temperatures below

150°C, while caramelization reactions occur when the product surface temperature

43

exceeds 150°C (Onishi M 2011). It will be important to monitor these color changes

differences that occur due to the removal of sugar from the product, which may affect the

caramelization reactions occurring at the higher temperature stage of the baking process.

A Minolta CM-2500d Spectrophotometer with Spectra Match software was

used to measure surface and interior color of the low and high β-glucan barley flour

muffin varieties in L a*b* color space. The International Commission on Illumination

(CIE) (1976) color space measures L for the luminance or lightness component with a

range 0 to 100 (dark to light), and a* (from green to red) and b* (from blue to yellow).

After preparing muffin samples as described above, measurements were taken for surface

color on top of the muffin and the interior crumb surface color from muffins that were cut

longitudinally from top to bottom. Measurements were taken as an average of three

locations across the surface of the same muffin. Differences between average L, a*, and

b* values were determined by comparing muffin treatments according to a t-test with a

significance level of 5% (p = 0.05) using the Microsoft Excel 2003 Data Analysis

ToolPak. It was predicted that the omission of sugar from the formulation will have a

significant impact on the surface and interior crumb browning, thus resulting in color

differences. The generation of brown pigments during a caramelization and Maillard

browning reactions will be lacking when stevia is used in the muffin formulation.

The colors for the two barley flours were also obtained by taking three

measurements across different locations on a Petri dish containing the flours. Visual color

differences of the barley flours and muffin surface and interiors were observed and

recorded with digital photographs using a Sony DSC-H50 digital camera with automatic

camera shutter speed settings and compared with L a* b* color values obtained from the

44

colorimeter to determine whether there were differences in the raw material and how they

would translate to changes occurring in the final product color.

2.10 Nutritional Comparison of Muffins

Nutritional values of barley muffin prototypes were evaluated using a software

called Recipe Calc, version 4.0 (Muller). Most ingredients’ nutrition facts were available

in the software database and were used as a basis for calculation of the finished product

nutrition facts. Ingredients that were not present in the database, such as specific

products including the Sustagrain barley flour, Bob’s Red Mill barley flour, and Bob’s

Red Mill Flaxseed Meal, were added into the software using the nutrition label provided

on the package or supplied by the manufacturer. All ingredients were added and the

nutrition labels were prepared based on the quantities used in the product formulations

and calculated automatically in the software. According to the Food and Drug

Administration, it is best to determine the values for nutrition labeling by conducting

laboratory analyses on its products, but a manufacturer can use average values calculated

from ingredient composition databases as long as it is confident that the values are

accurate and accurately represent the characteristics of the product (Mermelstein 2009).

Although the generated nutrition facts may not be an adequate tool for in labeling for

manufactured products, they provide a clear method of comparison among the different

formulations and varieties of the muffins for research purposes, particularly to identify

changes in carbohydrate levels, to denote differences in sugar and fiber levels.

45

2.11 Sensory Methodologies Used to Evaluate Muffin Products

Sensory evaluation is a scientific discipline used to evoke, measure, analyze, and

interpret reactions to those characteristics of foods and materials as they are perceived by

the senses of sight, smell, taste, touch, and hearing (Hui 2006). Sensory evaluation is a

technique that food scientists use the human body and its perception of the five basic

senses as a tool to measure differences and intensities of food characteristics. The

objective of the sensory panels pertaining to this research included looking at key

differences occurring due to the removal of sugar from the muffin formulations.

2.11.1 Quantitative Descriptive Analysis (QDA) Using Spectrum Method

Descriptive analysis methods involve the detection and the description of both the

qualitative and quantitative sensory aspects of a product by trained panels (Meilgaard,

Civille et al. 1999). Quantitative Descriptive Analysis (QDA) is the most sophisticated

sensory methodology. The results of QDA are a complete sensory description of the test

treatments (determined by the sensory panel), that provide a basis for relating specific

ingredients to specific changes in sensory characteristics of a product. QDA, particularly

the Spectrum Descriptive Analysis Method was chosen as the analysis tool for the study

since it yields quantitative data from panelist scores based on perceived intensities with

reference to pre-learned “absolute” intensity scales. The sensory findings may be used as

a comparison tool between the instrumental findings of the research and the human

response. Quantitative Descriptive Analysis does not provide information regarding

46

preference or liking of the product, but it is a tool to measure perceived intensities for

chosen attribute for a product.

2.11.2 Training Panel Members

Eight people with a general sensory background who regularly consumed baked

dessert products were recruited from an undergraduate course in the food science

department and voluntarily participated in the training process and sensory panel. A

semi-trained panel was formed and utilized for the sensory study. Each member of the

sensory panel underwent training sessions to familiarize with the terminology used to

evaluate the muffins. Training was conducted in a conference room setting with minimal

noise. At the training sessions: 1. panel members verbalized and discussed their

perceptions of a typical muffin by using descriptive words for the product; 2. descriptive

terminology was developed and agreed upon that best identified the observed perception

of the product being tested; 3. scales for recording intensities, as well as word/product

anchors for each scale category were determined and explained to panel members by the

panel leader. Attributes were chosen for the product in the following categories: 1)

appearance, 2) texture, 3) flavor/taste and 4) aroma. Once the panelists had agreed on the

meaning of the terms they had chosen to describe the muffin, a period of training

followed where panelists were given the definition of the chosen terminology and

reference samples were provided for each chosen attribute to demonstrate intensity levels

ranging from weak to strong. After training, the panelists were able to quantify the

degree to which the attribute was perceived in the product they were testing.

47

Three reference samples were chosen for each attribute to train panelists

according to Spectrum intensity scale values given in (Meilgaard, Civille et al. 1999).

Commercially available products were utilized and solutions for sweetness and bitterness

attributes were prepared using varying levels of sugar and caffeine in a water solution.

Reference samples were provided to panelists to be observed visually, smelled, and

consumed for training purposes.

Table 4: Reference standards for selected attributes used in Spectrum Descriptive

Analysis panel (Meilgaard, Civille et al. 1999; Gómez 2002)

Attributes Low Medium High

Sweetness Sucrose (2.0%) Sucrose (7.5%) Sucrose (16%)

Bitterness Caffeine (0.05%) Caffeine (0.1%) Caffeine (0.2%)

Firmness Cream cheese Processed American Cheese Raw Carrot

Springiness Cream cheese Marshmallow (mini)

Gelatin dessert

Surface Roughness Gelatin dessert Orange peel Granola bar

Color Intensity White bread Whole Wheat Bread

Pumpernickel Bread

Whole-Grain Complex Cream of Wheat Cooked whole

wheat spaghetti Triscuit Crackers

Banana Aroma 25% banana puree in water

50% banana puree in water Banana puree

48

Definitions for each selected attribute were provided to the panelists by the panel leader,

as described in Table 5 and agreed upon by all panel members.

Term Definition Sweetness The taste stimulated by sucrose and other sugars or sweet

substances. Bitterness The taste stimulated by substances such as quinine, caffeine, and

hop bitters. Firmness The force required to compress between tongue and palate. Springiness Degree to which sample returns to original shape after a certain

time period Surface Roughness

Degree to which surface is uneven.

Color Intensity The intensity or strength of the color from light to dark Whole-Grain Complex

Baked toasted barley flour: the aromatics of a grain which has been sufficiently heated to caramelize some of the starches and sugars.

Banana Aroma Odor associated with ripe banana

Table 5. Descriptors used to evaluate muffin samples in the Quantitative Descriptive

Analysis panel

2.11.3 Testing Procedure

To obtain quantitative measurements, a 15-cm horizontal line scale was utilized

with word bipolar word anchors previously determined by the sensory panel, always

moving from left to right with increasing intensity. The task of the panelist was to mark a

vertical line across the horizontal line scale at the point that best reflects the relative

intensity of the particular term. The mark is converted to a numerical value by measuring

the distance from the left end of the line. Panelists were provided paper ballots to record

their responses along with water, napkin, and spit cup. The sample was presented in a

plastic soufflé cup with a 3-digit random number code. In the first evaluation session,

49

muffin samples formulated with 100% sugar and prepared with high β-glucan Sustagrain

barley flour were evaluated by the panelists. In the second session, muffins prepared

with stevia and high β-glucan Sustagrain were evaluated by panel members. The same

formulation used for instrumental analysis was used the preparation of samples for the

sensory panels. Panelists were not aware whether they were evaluating a full sugar or no

sugar muffin.

50

1.1

1.12

1.14

1.16

1.18

1.2

1.22

1.24

1.26

Low b-Glucan High b-Glucan

Water Absorption Index (WAI)

CHAPTER 3

Results and Discussion

3.1 Water absorption values for barley flours

Water absorption values for low β-glucan Bob’s Red Mill brand barley flour and

high β-glucan Sustagrain barley flour were 1.16 and 1.25, respectively and were found to

have statistically significant difference (p<0.05).

Figure 9: Water absorption indices of high and low β-glucan barley flour

51

Table 6: Water Absorption indices of high and low β-glucan barley flour

As predicted, the water absorption index of the high β-glucan barley flour was

found to be significantly higher. This is due to the high water retention capacity of the β-

glucan present in the flour, where higher amounts of β-glucan have been shown to

demonstrate in increased amount of water absorption (KNUCKLES, HUDSON et al.

1997; Holtekjølen, Olsen et al. 2008; Sharma, Gujral et al. 2010). This difference in

water absorption of the low and high β-glucan barley flours was predicted to have an

effect on dough rheology where the high β-glucan barley flour will form a more viscous

or thicker batter due to its ability to retain more water into its molecular structure.

3.2 Increase in Muffin Height After Baking

There was no statistically significant difference (p<0.05) found among any of the

muffin sample variations, but there was a general trend observed between the muffins

prepared with 100% sugar having a higher % increase in muffin height, or rise. Also, a

trend was observed, although not statistically significant, where the muffins formulated

with low β-glucan barley flour had a higher % increase in muffin height,. This may be

explained by the role of batter viscosity where the lower viscosity batters generally tend

Water Absorption Index

Standard Error

Low β-Glucan 1.16 0.003

High β-Glucan 1.25 0.009

52

% Increase in Muffin Heights After Baking

0

10

20

30

40

50

60

70

100% Sugar No Sugar

% Increase in Height

Sustagrain

low B-glucan

to have a greater rise during the initial stages of the baking process. The batter prepared

with lower β-glucan was expected to have a lower viscosity since the water absorption

was found to be much lower. Also, sugar has a functional component in the system as it

provides structure to the air cell matrix, giving it structural support to incorporate air into

the product. When sugar was removed from the formulation, the lack of air cell structure

formation results in a decreased loaf volume thus resulting in decreased final height.

Muffin Variation % Increase in Height

Standard Error

High β-glucan 100% Sugar 53.77 8.88

High β-glucan 0% Sugar 46.42 3.10

Low β-glucan 100% Sugar 61.80 2.31

Low β-glucan 0% Sugar 51.46 6.62

Table 7: Percentage Increase in Muffin Height (Rise) After Baking

Figure 10: Percentage Increase in Muffin Height (Rise) After Baking

53

During baking there is considerable movement of the batter by convection

currents occurring in the oven. Development of these currents is dependent on the

temperature, batter type, and pan shape. Muffin batter can be considered as a high

viscosity batter, similar to cake batters utilized for traditional pound cakes. These kinds

of batters exhibit much less movement during baking compared to low viscosity batters,

which are used to produce high-ratio cakes. As the batter is heated, its viscosity

decreases during the initial stages of baking, as would be expected. However, the higher

temperature also triggers the leavening system and produces gas. As the bubbles increase

in size, the batter becomes a foam, which results in a higher apparent viscosity of the

system. As the temperature of the system increases, the starch gelatinizes, and much of

the free water becomes bound. This sets the baked product into a rigid system that does

not collapse as it cools. The top center of the muffin is the last to bake. If the muffin has

too little or too much water, a dip forms at the center, affecting the final height of the

product. Using the correct amount of water is important to produce a smooth contoured

crown which is desirable for a muffin-type of product (Hui 2007). Thus, water has an

important role in affecting how the product will rise and in turn, affect the textural

attributes of the product such as firmness.

3.3 Muffin Moisture Loss after Baking

Although there was no statistically significant difference (p>0.05) found in

percentage of moisture loss that occurred during baking, muffin samples showed a

general trend where formulations prepared with 100% sugar retained overall 2.5% more

54

moisture in the product after baking in contrast with muffins prepared with no sugar.

High and low β-glucan preparations also showed no statistically significant difference

(p<0.05) in the amount of moisture loss occurring in the muffins. Although there was no

statistical difference found in the sample means, there was an evident effect of sugar

content on the moisture retention in the samples more prominently as a functional

property of sugar rather than the amount of β-glucan present in the muffins. Higher β-

glucan content was thought to result in moisture retention in the product, due to the

ability of β-glucan to retain moisture and bind water in its structure. However, this trend

was not observed, as the moisture loss in both muffins prepared with the different barley

flours was very similar. It was found that β-glucan concentration had no effect on the

moisture retention in this baked product, but it was reaffirmed that sugar plays an

important functional role in retaining moisture following the baking process.

Table 8: Percentage Decrease in Muffin Weight (Moisture Loss) After Baking

Muffin Variation % Decrease in Weight

Standard Error

High β-glucan 100% Sugar 10.07 1.84

High β-glucan 0% Sugar 12.69 2.46

Low β-glucan 100% Sugar 10.27 1.24

Low β-glucan 0% Sugar 12.64 3.07

55

% Decrease in Muffin Weight After Baking

0

2

4

6

8

10

12

14

16

100% Sugar 0% Sugar

% Weight Loss

high B-glucan

low B-glucan

Figure 11: Percentage Decrease in Muffin Weight (Moisture Loss) After Baking

3.4 Rheological Properties barley flour doughs and muffin batters

Barley dough rheology was studied using the lubricated squeezing flow technique

to observe the role of water and its interaction with low and high β-glucan barley flours.

It was found that the viscosity of the high β-glucan barley flour had a significantly higher

biaxial viscosity at the maximum strain rate compared to low β-glucan barley flour

dough. This was expected due to the amount of β-glucans present in the dough and their

ability to absorb water which has been shown to increase dough viscosity due to its

ability to bind and hold water into the β-glucan structure. In several studies, it was found

that an increase in β-glucan concentration added to a wheat dough demonstrated the

formation of a more resistant dough, increased mixing stability, and increased work input

which may lead to resistance in proofing and ultimately loaf height and volume

56

(Izydorczyk, Hussain et al. 2001; Skendi, Papageorgiou et al. 2009). Wheat dough has

been reported to show viscosities ranging from 104 to 105 Pa s, dependent greatly on the

water absorption values (Osorio, Gahona et al. 2003; HadiNezhad and Butler 2009).

The low β-glucan dough showed a steady increase in viscosity as a function of

increasing strain rate, whereas the high β-glucan barley flour dough demonstrated an

initial rapid rise in viscosity, and then leveled off to a constant viscosity as the strain rate

was increased. The rheological properties of the flours may be related to the trend

observed in the muffin heights, where the low β-glucan muffins had an overall higher

percentage rise. This may have been due to the lower water absorption in the batter, thus

causing a lower viscosity batter, resulting in overall more water available during the

baking process. Viscosity has been explained to be the most important factor

contributing to overall volume of a baked product, where a higher viscosity batter results

in lower rise due to resistance to the oven’s convective currents occurring during the

baking process (Şumnu and Sahin 2008). From these results, it is evident that the

concentration of β-glucan in a dough or batter system has a great impact on the

rheological properties and will thus impact the way the model product behaves when it is

subjected to processing conditions such as batter mixing and baking.

57

1.E+04

1.E+05

1.E+06

0.005 0.006 0.007 0.008 0.009 0.01 0.011 0.012

Biaxial Strain Rate (s-1)

Biaxial Visco

sity (Pa s)

high b-glucan

low b-glucan

Figure 12: Biaxial Extensional Viscosity as a Function of Biaxial Strain Rate for

Sustagrain Dough and Bob’s Red Mill Barley Flour Dough

The consistency of the muffin batter is an important parameter which influences

the overall quality of the baked product by controlling the final volume. Higher viscosity

of the batter helps incorporating and supporting air into the food matrix, thus resulting in

higher volume and crumb structure. Consistency of batters containing at different levels

of β-glucan substitutions and sugar were compared. A non-Newtonian behavior was

noted for all batters, as consistency was determined to be dependent on shear rate. The

shear stress (σ) and strain (γ) data were fitted to the Power Law model (σ = K [γ]n) to

determine K (consistency index) and n (flow behavior index) values. The n and K values

of the different batter compositions with or without sugar are summarized below:

58

100

1000

10000

1 10 100 1000Shear Rate (1-s)

Strain (Pa)

LBG 100%

LBG 0%

HBG 100%

HBG 0%

Figure 14: Strain vs. shear rate relationship of muffin batter with varying levels of beta-

glucan and sugar

Batter Variation K (Pa sn) n

LBG 100% 166.86a 0.476a

LBG 0% 456.1b 0.3949b

HBG 100% 685.9c 0.383b

HBG 0% 1367.5d 0.2935c

Table 10: Consistency index and flow behavior index for muffin batter with varying

amounts of beta-glucan and sugar

All batter formulations indicated a non-Newtonian behavior, or shear thinning, as

the n-value was < 1.0 (Rao 1999; Kalinga and Mishra 2009). In agreement with the

findings of (Kalinga and Mishra 2009), who added β-glucan to a cake batter at levels up

to 40%, the flow behavior index and consistency significantly increased for batter

59

systems with increased levels of β-glucan. In the same manner, muffin batter consistency

increased with increasing level of β-glucans, reducing the ability of batter to flow as

indicated by higher K values. More so, the sugar also played a role where batters

prepared without sugar exhibited higher consistency, resulting in higher water uptake by

the β-glucan structure in the barley flour in the absence of sugar from the batter resulting

in less air being incorporated into the batter. Practically, this means that during the

mixing of the batter, a higher shear rate may be required to ensure that the batter is

combined thoroughly to ensure that the barley flour is properly hydrated.

Batter viscosity is a function of several variables including materials (especially

their protein, starch, and polysaccharide contents), particle size, the amount of water

present (solids concentration), and temperature. Free water might play a critical role in

the viscosity value of higher β-glucan barley flour batters because starch granules are not

soluble in cold water, where as β-glucans are and readily absorb water. Generally a

higher viscosity is caused by lower water content (Xue and Ngadi 2006). Thus, the

higher beta-glucan barley flour batter absorbed more water than the lower beta-glucan

flour, binding more water into its molecular structure and exhibited a higher overall

viscosity compared to that of the low beta-glucan batters as expected.

All barley flour muffin batters exhibited strain-dependent G’ (storage modulus)

and G” (loss modulus) behavior as those values are decreasing with increasing strain rate.

At shear rates where G’ is higher than G”, this indicates that the storage modulus (G’)

dominates, meaning that the material shows solid-like behavior and the deformations will

be essentially elastic or recoverable. However, if G” is much greater than G’, the energy

used to deform the material is dissipated viscously and the material's behavior is liquid-

60

like (Rao 1999). Likewise, when the loss modulus is higher at a given shear rate, the

material shows viscous-like behavior (Wyss, Larsen et al. 2007).

Overall, G’ and G” values were higher for batters prepared with the high β-glucan

barley flour. As seen in Figure 15 and Figure 16, batters prepared with low β-glucan

barley flour with sugar and without sugar, as well as high beta-glucan batter with sugar

demonstrated a more solid-like behavior at strain rates below 15%. At strain rates higher

than 15%, G” dominated, indicating that the batter properties were more liquid-like.

However, the high β-glucan batter without sugar had a higher overall G’ at strain rates

below 25%, which may indicate that the higher β-glucan content caused a more elastic

behavior at lower strain rates. At higher strain rates, G” was greater than G’ thus the

batter demonstrated a more viscous flow behavior rather than elastic. This may be due to

the water-binding and gel-forming abilities of β-glucan which are similar to gums in that

their viscoelastic properties are dependent on moisture content of the batter. In frequency

dependent sweep tests, increasing levels of β-glucan added to wheat dough up to 40%

also resulted in higher G’ values when measured at a 0.1% strain rate through the

duration of the run (Kalinga and Mishra 2009). Similarly, in a study where β-glucan was

added to wheat dough and measured for changes in G’ and G” behavior over a strain rate

of 0.5%, it was found that both the G’ (elastic modulus) and G” were increased

(Izydorczyk, Hussain et al. 2001).

61

100.00

1000.00

10000.00

0 20 40 60 80 100% Strain (1-s)

G' (Pa)

LBG 100%

LBG 0%

HBG 100%

HBG 0%

100

1000

10000

0 10 20 30 40 50 60 70 80 90 100% strain (1-s)

G" (Pa)

LBG 100%

LBG 0%

HBG 100%

HBG 0%

Figure 15: Effect of % Strain on G’ of muffin batters containing varying amounts of beta-

glucan

Figure 16: Effect of % Strain on G” of muffin batters containing varying amounts of

beta-glucan

62

3.5 Pasting properties of barley flours

The swollen granules and partially solubilized starch act as essential structural

elements of bread and other baked products. Starches have a functional role in providing

the crumb structure as well as crust formation along with proteins, particularly the

glutens. Low and high β-glucan barley flour slurries exhibited significantly different

pasting profiles due to the fact that the overall viscosity was significantly lower for the

low β-glucan barley flour slurry compared to the high β-glucan flour slurry. This may be

attributed to the amount of β-glucan present in the barley flour itself, which has been

shown to cause an increase solution viscosity with a high correlation (Sharma, Gujral et

al. 2010). Non-starch polysaccharides such as β-glucan have been explained to affect the

viscosity in the pasting profile. The peak time and pasting temperature were significantly

higher for the low β-glucan paste compared to the high β-glucan indicating that the lower

β-glucan barley flour had an inhibitory effect on gelatinization of the starches by

delaying the onset. This may be due to the fact that the low β-glucan barley flour itself

has a higher starch content. These results are consistent with the findings in a study

where 1 to 2% β-glucan was added to dispersions of 40% wheat and maize starch and

showed that the addition of β-glucan delayed the onset of gelatinization, but had no effect

on the pasting temperature (Symons and Brennan 2004).

63

Peak viscosity (mPa s)

Breakdown viscosity (mPa s)

Final viscosity (mPa s)

Setback viscosity (mPa s)

Peak time (min)

Pasting temperature

(°C) Low ββββ-glucan 6.15a 3.60a 6.75a 3.15a 20.50a 94.20a

High ββββ-glucan 25.04b 15.15b 27.14b 11.99b 18.50b 89.95b

High ββββ-glucan + sugar

31.64c 12.45c 28.04b 15.59c 18.00b 91.48b

Table 9: Pasting profile for low and high β-glucan barley flours

Change in letter within the column indicates a statistically significant difference within

the column

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0 5 10 15 20 25 30 35 40 45Time (min)

Viscosity (mPa s)

50.00

60.00

70.00

80.00

90.00

Low b-glucan

High b-glucan

HBG + Sugar

Temperature

Figure 13: Pasting profile for low and high β-glucan barley flours

The rheological properties of starch dispersions are greatly influenced by the

amount of starch present in the barley flour and their ability to swell while being heated.

Starch granules swell rapidly during the first stage of swelling when the water diffuses

into the center of the granules. At this point in the heating stage, the degree of leaching

of amylose out of the granules is low. As the starch granules continue to heat, it starts to

64

deform and lose its original shape. Different granule structures in the starch greatly

influences the pasting profile. For example, if starch granules tend to hydrate with ease,

swell rapidly, and rupture to a great extent, the starch paste will lose viscosity relatively

easily during the cooling phase of the pasting curve. It was seen that the addition of

sugar in the high β-glucan barley flour resulted in rapid increase in viscosity during the

heating phase and also a more rapid loss in viscosity during the constant temperature

phase of the pasting curve compared to the low and high β-glucan barley flour slurries.

3.6 Color values for Barley Flour Varieties

The colors of the two barley flours showed significant color differences in the

instrumental values obtained with a colorimeter, consistent with their visual appearance.

The L* value was significantly higher (p<0.05) for the low β-glucan Bob’s Red Mill

brand barley flour, indicating that it is visually lighter in color. Similarly, the b* value

for the Sustagrain high β-glucan barley flour was significantly higher (p<0.05), indicating

a more yellow color. The a* values for both flours indicated that there was no statistical

difference in the redness values. The difference in flour colors was predicted to affect the

surface and interior colors of the baked muffin product and may be caused by the use of a

different barley strain or milling process.

65

0

10

20

30

40

50

60

70

80

90

100

L a b

Low b-glucanBob's Red Mill

High b-glucanSustagrain

L Standard

Error a

Standard

Error b

Standard

Error

Low β-glucan 91.02 0.63 1.13 0.19 10.31 0.60

High β-glucan 88.3a 0.24 1.43 0.06 16.26a 0.17

Table 11: Average L a*b* Values for low β-glucan and high β-glucan Barley Flour

Varieties

A change in letter within the columns indicates a statistically significant difference

(p<0.05)

Figure 17: Average L a*b* Values for low β-glucan and high β-glucan Barley Flour

Varieties

66

Figure 18: Visual Difference in Flour Color. Left: Bob’s Red Mill low β-glucan Barley

Flour. Right: Sustagrain high β-glucan Barley Flour

3.7 Muffin Surface Color

Muffin surface colors were evaluated visually and with a colorimeter to determine

changes occurring due to the removal of sugar from the formulation and also as an effect

of flaxseed meal addition. The effect on color from using low and high β-glucan flours

in the muffins was also compared. It was predicted that when sugar was removed from

the formulation, there will be difference in the color values as a function of the Maillard

browning and caramelization reactions occurring during the processing.

It was found that the L, a*, and b* values were significantly different for muffins

prepared with low β-glucan 100% sugar muffins compared to the 0% sugar. The L value

(lightness) was significantly lower (p < 0.05) for the muffins prepared with 100% sugar,

compared to the 0% sugar as well as the 0% with flaxseed meal. There was no

67

0

5

10

15

20

25

30

35

40

45

100% sugar 0% sugar 0% w/ flaxseed

L

a*

b*

significant difference found in the a* and b* values between the 100% sugar and 0% with

flaxseed muffins.

The difference in surface colors may be explained by sugar’s role in the

caramelization and browning reactions. When sugar was omitted from the formulation,

the muffins had significantly higher L values, indicating that they are lighter in surface

color. Although flaxseed itself has a darker appearance and was thought to contribute to

the darker surface color, the muffins prepared with 100% sugar indicated a darker color.

Figure 19: Surface color values for muffins prepared with low β-glucan Bob’s Red Mill

brand barley flour

68

Figure 20: Muffins prepared with low β-glucan Barley Flour. Left: 100% Sugar, Middle:

0% Sugar, Right: 0% Sugar + Flaxseed Meal

Muffins prepared with high β-glucan barley flour showed a significant difference

(p<0.05) in the a* surface color value, or redness component, where the 0% sugar

muffins showed a higher value compared to that of the 100% sugar. There was also a

significant difference when comparing the L value for the 100% sugar with the 0% sugar

with flaxseed meal, where the muffin surface for the 100% sugar had a significantly

lower L* value, indicating a darker surface color. This may have been caused by the

additional caramelization browning reaction occurring due to the presence of sugar.

Although there was no significant difference in the a* (redness) value between the 100%

sugar muffin compared to the 0% sugar, there was a significant difference in the a* value

for the muffin with 0% sugar + flaxseed meal, which had a higher a* value. This may be

attributed to the flaxseed meal contributing to the redness of the surface color. The b*

value, or the yellowness component, did not indicate any difference among the variations.

69

0

5

10

15

20

25

30

35

40

45

100% sugar 0% sugar 0% w/ flaxseed

L

a

b

Figure 21: Surface color values for muffins prepared with high β-glucan barley flour

Figure 22: Muffins prepared with high β-glucan Barley Flour. Left: 100% Sugar, Middle:

0% Sugar, Right: 0% Sugar + Flaxseed Meal

70

Muffin surface color values prepared with 100% sugar using the different low and

high β-glucan barley flours were significantly different in their L, a*, and b* values

(p<0.05). High β-glucan barley muffins had higher L and b* values, whereas the low β-

glucan muffins had higher a* value for surface colors. This may be due to the difference

in original barley flour colors between the two brands. However, the surface colors for

no sugar varieties only showed a significant difference in the L value, where the low β-

glucan barley flour had a higher lightness value compared with the muffin surface

prepared with high β-glucan barley flour.

L Standard Error a* Standard

Error b* Standard Error

Low β-glucan 100% Sugar

27.72a 1.38 14.89a 0.97 38.91a 1.72

High β-glucan 100% Sugar

37.70 1.09 13.30 0.12 40.41 0.93

Table 12: Average L, a*, b* color values for surface color of muffins prepared with low

or high β-glucan barley flour with 100% sugar

Change in letter indicates significance at (p < 0.05) within the columns.

L Standard Error a* Standard

Error b* Standard Error

Low β-glucan 0% Sugar

40.77 0.76 10.89a 0.97 33.66a 0.89

High β-glucan 0% Sugar

38.36 1.40 13.93 0.16 40.68 0.68

Table 13: Average L, a*, b* color values for surface color of muffins prepared with low

or high β-glucan barley flour with 0% sugar

Change in letter indicates significance at (p < 0.05) within the columns.

71

Comparison of the low β-glucan and high β-glucan muffins with 0% sugar

indicated that there was a significant difference in the a* and b* values of the surface

color of the muffins, where the high β-glucan muffins prepared with Sustagrain barley

flour had higher a* and b* color values. This color difference may be due to the variation

in original barley flour colors between the two brands. Similarly, differences were seen

in the 100% sugar muffins as well.

Crust color formation is an important factor contributing to appearance as well as

flavor, aroma, and taste. The main component responsible for this critical reaction is

sucrose, which undergoes caramelization through a series of dehydration and

polymerization or condensation reactions. Another reaction that is also responsible for

crust color formation is the Maillard reaction, which occurs due to a reaction between the

aldehyde or ketone group in reducing sugars and the amino acids present in proteins from

the eggs and flour. During the baking process, as temperatures reach and exceed 100°C,

the water activity is lowered, which makes ideal conditions for these browning reactions

to occur (Hui 2006).

3.8 Muffin Interior Color

Muffins prepared with low β-glucan Bob’s Red Mill brand barley flour showed

no statistically significant difference (p>0.05) in the interior crumb color L, a*, or b*

values between the 100% sugar and the 0% sugar formulations. However, there was a

significant difference (p<0.05) when comparing the 100% sugar control to the muffin

prepared with flaxseed meal, where the a* and b* values were lower in the flaxseed

72

0

5

10

15

20

25

30

35

40

45

50

100% sugar 0% sugar 0% + flaxseed

L

a

b

formulation. Although not significant, there was a trend where the muffins prepared

without sugar had a higher interior L or lightness value. This may be due to the lack of

browning reactions taking place caused by the removal of sugar from the product and is

consistent with the outer surface lightness values for the low β-glucan muffins.

As seen in Figure 22, muffins prepared with high β-glucan barley flour with 0%

sugar and the addition of flaxseed meal showed a significantly lower L value and higher

a* and b* values compared to the 100% sugar control, possibly due to the darker color of

the flaxseed meal itself, resulting in a darker crumb color.

Figure 23: Interior color values for muffins prepared with low β-glucan barley flour

73

0

10

20

30

40

50

60

100% sugar 0% sugar 0% w/ flaxseed

L

a

b

Figure 24: Interior Surface Images of Muffins Prepared with low β-glucan barley Flour.

Left: 100% Sugar, Middle: 0% Sugar (Stevia), Right: 0% Sugar + Flaxseed Meal

Figure 25: Interior color values for muffins prepared with high β-glucan barley flour

Table 14: The average L, a*, b* color values for interior color of muffins prepared with

low or high β-glucan barley flour with 100% sugar

L Standard Error a* Standard

Error b* Standard Error

Low β-glucan 100%

29.00a 2.65 16.53 1.34 40.55 0.56

High β-glucan 100%

46.46 1.75 10.23 0.57 34.58 1.68

74

Table 15: The average L, a*, b* color values for interior color of muffins prepared with

low or high β-glucan barley flour with 0% sugar

Figure 26: Interior Surface Images of Muffins Prepared with high β-glucan barley flour.

Left: 100% Sugar, Middle: 0% Sugar (Stevia), Right: 0% Sugar + Flaxseed Meal

3.9 Muffin Firmness Muffins showed a general trend where firmness was found to be higher for

formulations prepared without sugar, as predicted. Firmness values ranged from 640-

1120 g peak force, which are comparable values found in literature for high-fiber

muffins (Grigelmo-Miguel, Carreras-Boladeras et al. 1999) and (Baixauli, Sanz et al.

2008). There was a significant difference (p<0.05) in peak force, or firmness, between

the high β-glucan muffins prepared with 100% sugar when compared to that with 0%

L Standard Error a* Standard

Error b* Standard Error

Low β-glucan 0% Sugar

34.13 4.17 16.46 2.26 37.96 2.24

High β-glucan 0% Sugar

41.44 0.45 11.49 0.57 33.96 1.29

75

sugar (stevia) and 0% sugar with flaxseed meal. This indicates that there is a significant

textural difference when sugar is omitted from the formulation, resulting in higher muffin

firmness. However, there was no difference in muffins among the muffins prepared with

varying β-glucan levels even though it was predicted that the higher β-glucan barley flour

would result in greater firmness due to the increased water absorption and more viscous

batter. This indicates that there is a greater effect of sugar’s role in a baked product

rather than the functionality of β-glucan resulting in higher firmness.

An important observation was that the muffin formulated using high β-glucan

barley flour with 100% sugar and 0% sugar + flaxseed meal were also significantly

different in firmness values similar to the low β-glucan barley flour muffins where the

0% sugar + flaxseed meal muffins showed a higher peak force, or firmness, compared to

the 100% sugar variety. Flaxseed has been shown to result in a higher water absorption,

thus increasing firmness due to a significant increase in batter viscosity when flaxseed

meal was added at 5% of the batter formulation (Shearer and Davies 2005). The

similarity in firmness between the 0% sugar muffin and the muffin prepared with

flaxseed meal may be explained by the fact that the addition of flaxseed meal provided

the necessary bulk in the product when sugar was omitted from the formulation.

Structurally, the addition of the flaxseed meal may result in similar muffin volume and

cell structure of the full-sugar variety. In fact, flaxseed mucilage in bread has been

shown to cause a softening effect, and the rate of firming was reduced compared with a

control bread (Shearer and Davies 2005).

76

-100

100

300

500

700

900

1100

0 1.5 3 4.5 6Time (s)

Force (g)

100% Sugar HBG

0% Sugar HBG

Figure 27: Typical texture profile curve for high β-glucan muffins prepared with 100%

sugar and 0% sugar

Peak Force (g) Standard Error

Low β-glucan 100% sugar 825.30a 45.79

Low β-glucan 0% sugar 920.87a 97.75

Low β-glucan 0% sugar + flaxseed meal 1125.20a 107.08

High β-glucan 100% sugar 643.80a 26.07

High β-glucan 0% sugar 1004.97abc 41.24

High β-glucan 0% sugar + flaxseed meal 1008.90abc 6.52

Table 16: Average maximum peak force to compress muffins as a measure of firmness

77

0

200

400

600

800

1000

1200

low b-glucan100%

Low b-glucan0%

low b-glucan0% flax

high b-glucan100%

high b-glucan0%

high b-glucan0% flax

Muffin Variation

Peak Force (g)

Figure 28: The average maximum peak force to compress muffins as a measure of firmness

The functional role of sugar was found to be very important for the textural

attributes of the muffins. Sugar affects the texture by causing the grain and crumb

structure to become smoother, softer, and whiter. This is attributed to the action of sugars

in delaying the gelatinization of starch and the denaturation of protein. Sugar is also

responsible for a tenderizing effect in a baked product (Pyler 1973).

3.10 Nutrition Facts for Muffin Formulations

An important nutritional difference was seen in the calorie content and

carbohydrate levels when sugar was omitted from the formulation. A 33% and 35%

reduction in carbohydrates was seen when stevia was used as a sweetener in the low β-

glucan muffins and high β-glucan muffins, respectively. A 19% and 18% reduction in

calories was seen when stevia was used as a sweetener in the low β-glucan muffins and

78

high β-glucan muffins, respectively. Furthermore, the high β-glucan muffins provide

nearly 6 grams of fiber, which can be considered as 20% of the daily recommended value

of fiber intake (based on an average 30 grams) (Sibylle, Diane et al. 2005). The variation

in the fat content of the muffins was due to the type of barley flour used, where high β-

glucan Sustagrain barley flour contained more fat in the raw material as well as the

addition of flaxseed meal into the muffin formulation.

Serving Size: 4 mini muffins

100% Sugar LBG

0% Sugar LBG

100% Sugar HBG

0% Sugar HBG

0% Sugar LBG + Flax

0% Sugar HBG + Flax

Calories (kcal) 172 139 182 149 151 160

Calories from Fat (g) 59 59 69 69 66 76

Total Fat (g) 6.6 6.6 7.7 7.7 7.3 8.4

Saturated Fat (g) 1 1 1.3 1.3 1 1.3

Cholesterol (mg) 32 32 32 32 32 32

Sodium (mg) 169 169 169 169 169 169

Total Carbohydrates (g) 25.5 17.2 23.9 15.6 17.9 16.3

Dietary Fiber (g) 3.2 3.2 5.7 5.7 3.9 6.4

Protein (g) 2.8 2.8 4.3 4.3 3.3 4.8

Table 17: Nutrition Facts for Muffin Formulations (LBG = low β-glucan, HBG = high β-

glucan)

Each serving of the above formulations prepared with flaxseed meal provides 400

mg of omega-3 fats, calculated based on the Bob’s Red Mill brand flaxseed meal

nutrition facts of 2400 mg per 2 Tbsp serving. This amount of omega-3 fatty acids is a

significant contribution to the daily intake.

79

3.11 High ββββ-glucan Muffin Sensory Quantitative Descriptive Analysis

The objective of a sensory descriptive analysis panel was to determine the key

differences in products when the functional ingredient sugar is removed from the product

formulation as well as to look at the key attributes of a baked product using barley flour.

Many studies have been previously reported with baked products prepared with a certain

percentage of a high-fiber flour or fruit dietary fiber component added into the

formulation. However, there have been limited applications where only a high-fiber

containing flour was used exclusively in the formulation. This presents many challenges

from a technical aspect such as determining processing parameters as well as from a

sensory point of view, where the high fiber components adversely affect the product

texture in terms of springiness, firmness, as well as color resulting in diminished sensory

appeal (Alpers and Sawyer-Morse 1996; Grigelmo-Miguel, Carreras-Boladeras et al.

1999; Baixauli, Salvador et al. 2008; Baixauli, Sanz et al. 2008). It is important that

when sugar is removed from a conventional product, that there is a significant health

benefit while maintaining the integrity and quality of a conventional product. As

mentioned, a significant nutritional difference was seen in the carbohydrate content of the

muffins when sugar was omitted from the formulation. However, there is also a concern

of product acceptability. If the product will be rejected by the consumer due to negative

attributes resulting from the removal of a functional ingredient, there would be no benefit

from the product. The sensory panel helps to serve as a tool to monitor some of the

changes that can be detected during consumption as a result of change in product

80

formulation. It is a key tool that may be used in product optimization as the sensory

profile of a product is the most important factor governing consumption.

Muffins prepared with high β-glucan barley flour containing 100% sugar and 0%

sugar, sweetened with stevia, were evaluated with an eight member descriptive panel for

chosen attributes to compare the effect of the removal of sugar from the formulation. It

was found that the panel rated the surface roughness, firmness, and bitterness attributes as

significantly higher for the muffins sweetened with stevia. These results are in agreement

with the instrumental findings for the muffin firmness values as well as visual surface

roughness caused by the formation of tunnels and cracks in the no sugar muffins. Tunnel

formation in muffins is explained by the buildup of gases inside the crumb structure of

the muffin. Because barley flour may be considered as hard flour due to its higher fiber

content, steam becomes trapped inside the matrix during the baking process. When

enough pressure builds up, the gas escapes from the top, leaving a path from which it

escaped, known as a tunnel, which is an undesirable attribute in a muffin. Since sugar

has the capability of retaining moisture by binding water and acting as a humectant, when

it is removed from the muffin formulations, there is also unbound water present, which

may lead to previously described tunnel formation or cracks on the tops of the muffins

(Figoni 2010). Stevia has been described to have a lingering bitterness and licorice

aftertaste (Elkins 1997). This is consistent with the findings of this sensory panel, where

panelists indicated a significantly increased bitterness attribute intensity of the muffins

prepared with stevia in the formulation.

81

0.00

2.00

4.00

6.00

8.00

10.00Surface Rougness

Color Intensity

Springiness

Firmness

Sweetness

Bitterness

Whole-Grain

Banana Aroma

100% Sugar

0% Sugar

Figure 29: The mean values of attributes measured by the QDA panel for muffins

prepared with high β-glucan barley flour with 100% sugar and 0% sugar, sweetened with

stevia

Attribute 100% Sugar Standard Error Stevia Standard Error

Surface Rougness 4.68 1.65 9.26 3.27

Color Intensity 8.91 3.15 8.75 3.09

Springiness 7.86 2.78 8.39 2.97

Firmness 5.89 2.08 8.10 2.86

Sweetness 4.63 1.64 3.31 1.17

Bitterness 1.21 0.43 6.64 2.35

Whole-Grain 5.88 2.08 7.81 2.76

Banana Aroma 7.70 2.72 4.39 1.55

Table 18: The mean values of each attribute measured by the QDA panel for muffins

prepared with Sustagrain flour with 100% sugar and 0% sugar, sweetened with stevia

82

Another important observation from the results of the descriptive panel findings

was that some of the flavor and aroma attributes were found to be different in the muffins

prepared with stevia. The only variation in the formulation was the removal of sugar and

the other ingredients were kept constant. So, although no statistical significant difference

was found for the sweetness, whole-grain, or banana aroma attributes, it is important to

note that these attributes were rated lower for muffins prepared with stevia. Panelists

indicated in their comments that the lingering taste of stevia may have caused a masking

effect of the banana aroma in the product. Similarly, the whole-grain complex flavor

may have been accentuated by the bitterness of the stevia, leading to a higher score for

the muffins prepared with stevia. Also, the color intensity and springiness attributes were

found to be rated very similarly for both muffin varieties. This may be an important

factor to consider because although there may be instrumental differences in surface and

interior crumb color, there is an undetectable difference in the visual sensory perception

of the two variations.

Bitterness may be considered as a negative aspect of product and may lead to

rejection of the food and prevent consumption. Thus, additional processing and

formulation changes would be necessary to mask the bitterness of stevia. There are

several ways to overcome this obstacle. One way would be to do a blend of sugar and

stevia to find a balance between the functional properties of sugar and the health benefits

associated with using stevia. This would also be helpful in preventing the delayed onset

of sweetness caused by the use of stevia, while maintaining sweetness levels.

Additionally, by using lower stevia-extract levels, the product has significantly less

bitterness and licorice off-notes coming from the stevia (Horn 2010). Few panelists also

83

noted that the bitterness caused by stevia masked the banana flavor in the muffin. This

was seen as a trend in the muffins prepared with stevia where the banana aroma rating

was lower, although not significant.

There are two approaches to improving the overall sweetness taste functionality

of stevia. The first is by modifying the structural components of the stevioside

compounds that are responsible for imparting a sweet taste perception and using a pure

extract with a maximum Rebaudioside A content, which has been reported to have a

clean and minimal bitter aftertaste. Generally, the quality and magnitude of sweetness

reaches a maximum with three to four monosaccharide units at the C-13 position of

steviol and one to two monosaccharide units at the C-19 position (Kinghorn 2002).

Figure 30: Sweet steviol glycosides from leaves of Stevia rebaudiana.(Kinghorn 2002)

Another approach to mask the bitterness characteristics of stevia is by using

specific novel bitterness blockers in the formulation, which are currently manufactured

by flavor companies, fragrance houses, and ingredient companies. These types of

84

compounds work by blocking the specific bitterness receptors on the tongue where the

bitterness flavor sensation is perceived. By using a combination of aroma chemicals,

plant extracts, bitter blockers, and mouthfeel enhancers, food products with stevia

extracts can have a sweetness profile that is more similar to that of sugar. Besides

improving the sweetness profile, these ingredients can be used to enable the use of less

expensive stevia extracts without compromising the taste. In fact, companies specializing

in extraction technologies offer bitter blockers that have the consumer-friendly label of

natural flavors.

One such compound is called thaumatin, which is a sweet protein derived from

the African serendipity berry, Thaumatococcus daniellii and it has been successful for

use in products at low concentrations to mask the bitterness caused by stevia (Suami,

Hough et al. 1997). This natural label helps maintain the healthful consumer perception

of the product. The mechanism by which these ingredients function is by binding to the

bitter taste receptors on the taste buds, thereby decreasing the perceived bitterness of the

lower stevia extracts (Horn 2010) and (Tallon 2009). In fact a 0.2% thaumatin solution

has been shown to result in approximately a 40% decrease in bitter response of stevia.

However, this study has been done only using a solution rather than actual products.

Also, to date, there has been limited scientific research on the chemical components of

such novel bitterness blockers. Much of the research has been patented by flavor and

ingredient companies as proprietary products that are used mainly for beverage

applications. Further in-depth analysis is required to study the mode of action of such

bitterness blockers or masking agents in baked products.

85

3.13 Conclusions and Suggestions for Future Work

Relating back to the project objectives, several key observations were seen as the

beta-glucan and sugar levels varied. First were the significantly different viscosity, flow

behaviors, and pasting profiles of the barley flours as well as the affect of sugar in these

processes. One of the key components affecting these properties was water, which

resulted in a higher viscosity for the high β-glucan barley flour batters. In this case,

processing parameters such as mixing speed and time may need to be adjusted to ensure

that the batter is properly mixed, allowing for the flour to be well-hydrated. Second was

the impact of sugar and how it affected the product texture when it was removed from the

formulation. There were significant changes seen in texture, muffin rise, as well as

differences in some of the color characteristics. More importantly, these changes were

more prominent as a result of sugar removal from the system rather than as an influence

of the β-glucan content as predicted.

It is also important to note that some of the key sensory attributes selected in this

study may be comparable to the instrumental findings. For example, the muffin firmness

was rated similarly by the descriptive panel with the same observation seen in the

instrumental texture profile where muffins prepared without sugar had a significantly

higher firmness. However, the color was rated very similarly by the panelists for both the

varying sugar levels. This may be an indicator that although there may be some

statistically significant differences found instrumentally, it may not be detected by human

perception. Future work may include correlating some of the instrumental measurements

with sensory attributes as rated by a trained panel.

86

Water uptake by the high β-glucan barley flour was also found to be much higher,

which affected the rheological properties, and in turn the product texture and height. This

provides an area for further study, where the water level may need to be optimized to

obtain a product that has a similar texture to a conventional baked product. Also, there is

an opportunity for improving and overcoming some of the challenges caused by using

stevia in a baked formulation. The use of bitterness blockers and sweetness enhancers

has been very limited in baked products and may prove to be helpful in reducing some

the negative attributes.

87

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