IMPROVEMENT OF PHYSICO-CHEMICAL PROPERTIES OF
PALM OLEIN BLENDED WITH RICE BRAN OIL
By
Surin Watanapoon
A Master’s Report Submitted in Partial Fulfillment of the Requirements for the Degree
MASTER OF SCIENCE
Department of Food Technology
Graduate School
SILPAKORN UNIVERSITY
2004
ISBN 974 – 464 – 509 - 1
การปรับปรงุคณุลักษณะทางกายภาพ และ ทางเคมีของน้าํมันปาลมโอเลอีน ผสมกับน้ํามนัรําขาว
โดย นายสุรินทร วฒันพูล
สารนิพนธนี้เปนสวนหนึง่ของการศึกษาตามหลักสูตรปริญญาวิทยาศาสตรมหาบัณฑิต สาขาวิชาเทคโนโลยีอาหาร ภาควชิาเทคโนโลยีอาหาร
บัณฑิตวิทยาลัย มหาวิทยาลัยศิลปากร ปการศึกษา 2547
ISBN 974 – 464 – 509 – 1 ลิขสิทธ์ิของบณัฑิตวิทยาลัย มหาวิทยาลัยศิลปากร
The graduate school, Silpakorn University accepted master’s report entitled
“IMPROVEMENT OF PHYSICO-CHEMICAL PROPERTIES OF PALM OLEIN
BLENDED WITH RICE BRAN OIL” by Surin Watanapoon in partial fulfillment of
the requirements for the degree of master of science, program of food technology.
……………………………………. (Asso. Prof. Chirawan kongklai, Ph.D.)
Dean of graduate school
……./……./…….
Master’s Report advisor
Bhundit Innawong, Ph.D.
Master’s Report committee
…………………………………. Chairman
(Arunsri Leejeerajumnean, Ph.D.)
………/……../………
…………………………………. Member
(Bhundit Innawong, Ph.D.)
………/……../………
…………………………………. Member
(Sopark Sornwai, Ph.D.)
………/……../………
IV
K 44403357 : สาขาวิชาเทคโนโลยีอาหาร คําสําคัญ : น้ํามันปาลมโอเลอีน / น้ํามันรําขาว / ความคงตัวตอความเย็น / ความคงตัวตอความรอน สุรินทร วัฒนพูล : การปรับปรุงคุณลักษณะทางกายภาพและทางเคมีของน้ํามันปาลมโอเลอีนผสมกับน้ํามันรําขาว (IMPROVEMENT OF PHYSICO-CHEMICAL PROPERTIES OF PALM OLEIN BLENDED WITH RICE BRAN OIL) อาจารยผูควบคุมสารนิพนธ : อ. ดร. บัณฑิต อินณวงศ. 104 หนา. ISBN 974-464-509-1
น้ํามันปาลมโอเลอีน เปนน้ํามันที่ใชมากในอุตสาหกรรมการทอด อยางไรก็ตาม น้ํามันปาลมโอเลอีนก็มี
ขอจํากัด คือการงายตอการตกผลึกที่ดานลางของภาชนะบรรจุหรือเมื่อเก็บไวเปนเวลานาน การศึกษาวิจัยนี้ไดคนหาการตานทานการตกผลึกของน้ํามันปาลมโอเลอีนโดยผสมกับน้ํามันรําขาวในอัตราสวนตาง ๆ กัน รวมถึงการประเมินคุณภาพของน้ํามันดาน ความคงตัวตอความรอนของน้ํามันปาลมโอเลอีนที่ผสมกับน้ํามันรําขาวอีกดวย
จากการศึกษาการตานทานการตกผลึกของน้ํามันปาลมโอเลอีนเมื่อผสมกับน้ํามันรําขาวในอัตราสวนตางกัน โดยศึกษาถึงการเปลี่ยนแปลงดาน การทดสอบที่อุณหภูมิตํ่า จุดขุนมัว และ ความคงตัวตอความรอน โดยการที่จะใหความรอนที่อุณหภูมิ 180 องศาเซลเซียส และ โดยไมมีการกวน ทําการทดสอบสมรรถนะการทอดดวยการทอดดวยมันฝรั่งสด ซึ่งจะประเมินคุณลักษณะทางกายภาพและทางเคมีของน้ํามันดวย การเปลี่ยนแปลงของสีทั้งหมด ความหนืด จุดการเกิดควัน ปริมาณกรดไขมันอิสระ และ คาเปอรออกไซด
การใชน้ํามันรําขาวในปริมาณที่สูง จะชวยชะลอการเกิดผลึกสีขาวในน้ํามันปาลมโอเลอีน โดยมีการลดลงของจุดขุนมัว เมื่อเทียบกับน้ํามันปาลมโอเลอีน 100 เปอรเซ็นต โดยน้ํามันรําขาวจะแสดงผลลบตอการทดสอบที่อุณหภูมิตํ่า จึงไมเหมาะตอการนําไปทําน้ําสลัด น้ํามันรําขาวสามารถปรับปรุงคุณลักษณะทางกายภาพและทางเคมีของน้ํามันผสม โดยทําใหน้ํามันผสมมีความคงตัวตอความรอนสูงขึ้นเมื่อเทียบกับน้ํามันปาลมโอเลอีน 100 เปอรเซ็นต การผสมน้ํามันปาลมโอเลอีนกับน้ํามันรําขาว 50 เปอรเซ็นต จะใหผลตอการเปลี่ยนแปลงปริมาณกรดไขมันอิสระ คาเปอรออกไซด และความหนืด เล็กนอย เพราะฉะนั้น น้ํามันรําขาวนอกจากสามารถปรับปรุงการตานทานการตกผลึกแลว แตยังชวยปรับปรุงความสามารถในการตานทานความรอนใหกับน้ํามันผสม เมื่อเทียบกับน้ํามันปาลมโอเลอีนอีกดวย ภาควิชาเทคโนโลยอีาหาร บัณฑิตวิทยาลัย มหาวิทยาลัยศิลปากร ปการศึกษา 2547
ลายมื่อช่ือนักศึกษา …………………………………
ลายมือช่ืออาจารยผูควบคุมสารนิพนธ …………………………………….
V
K 44403357: MAJOR: FOOD TECHNOLOGY
KEY WORD: PALM OLEIN / RICE BRAN OIL / COLD STABILITY / THERMAL
STABILITY
SURIN WATANAPOON : IMPROVEMENT OF PHYSICO-CHEMICAL OF
PALM OLEIN BLENDED WITH RICE BRAN OIL. MASTER’S REPORT
ADVISOR: BHUTDIT INNAWONG, Ph.D. 104 pp. ISBN 974-464-509-1
Palm olein (PO) was widely used in frying industry. However, it proned to
form a fat crystals at the bottom of the container or after long periods of storage. This
study was investigated to determine the resistance on crystallization of the blended oil
between palm olein and rice bran oil (RBO) at various proportions. Their thermal and
cold stabilities of the blended oils were also evaluated.
The resistance to crystallization of PO blended with RBO at various
proportions was determined by means of monitoring the changes in cold test and
measuring the cloud point. The thermal stability was conducted by continuous heating
without agitation and frying at 180oC. The changes in physico-chemical properties of
oils were detected by several physical and chemical indexes consisting of overall color
difference, viscosity, smoke point, free fatty acid content (FFA), and peroxide value
(PV).
The blended oils with high RBO were able to retard the formation of white
crystals and resulted in the reduction of the cloud point as compared with the control
(100% PO). The additional RBO in blended oil represented the negative responses in
cold test, and these oils could not used for the salad oil manufacturing. RBO improved
the physico-chemical properties of the blended oils and exhibited high thermal stability
as compare with the control. Blending PO with 50% RBO strongly was recommended
as the minimum changes in FFA, PV, and viscosity. Therefore, the blending of RBO
in PO was the potential technique to improve not only the resistance from
crystallization but also elevated thermal stability of blended oil.
Department of Food Technology Graduate School, Silpakorn University Academic Year 2004
Student’s signature ………………………………
Master’s Report Advisor’s signature …………….………………..
VI
ACKNOWLEDGEMENTS
I wish to express my sincere thanks to my advisor Dr. Bhundit Innawong for
his kindness, ideas, and knowledgeable advice everywhere my Mater’s program. I
gratefully thanks for the time to make suggestions and help me for the master report
preparations.
I gratefully thank for my committee Dr. Arunsri Leejeerajumnean and Dr.
Soprak Sornwai. I would like to thank all graduate school and my friends that assisted
in this research. I many thank all staffs and faculty in Food Technology department
for the good things during I spent time at the department.
I sincerely thank Pamola Company Limited that time and resource support
during this research. I would like to thank all works staffs who to work together and to
share happiness and trouble throughout my job.
Many thanks all of my parents, my wife’s parents, and relations for their love,
opportunity, spirit, and financial support that they are given me throughout my
program. Finally, I lovely thank my wife who to share happiness and trouble and spirit
that she has given me every times.
VII
TABLE OF CONTENTS
Page
Thai Abstract ……..........................................................…................………….........IV
English Abstract …….………….……………………………………………………..V
Acknowledgements ……….........................................................................................VI
List of tables ……….................................................….............................................VIII
List of figures ………..................................................................................................IX
Chapter
1 Introduction ………............................................................................................1
2 Literature review …………................................................................................3
2.1 Palm oil ………................................................................................3
2.2 Rice bran oil ...................................................................................17
2.3 Blended oil .....................................................................................22
2.4 Crystallization of fats and oils .......................................................23
References ………................................................................................25
3 Resistant to crystallization of palm olein blended with rice bran oil ………..29
4 Thermal stability of palm olein blended with rice bran oil ….…………........41
5 Summary …………………...….......................................................................64
Appendix
Appendix A ...............………..........................................................................65
Appendix B ......…...........................................................................................76
Vita ..............................…..........................................................................................104
.
VIII
LIST OF TABLES
Table Page
2.1 Fatty acid composition of palm oil. ........................................…........................4
2.2 Triglyceride composition of crude palm oil. .............….....................................7
2.3 Major physical properties of palm oil. ..................…..........................................8
2.4 Refining crude palm oil: unit process. ......................................…....................12
2.5 Fatty acid composition and physical characteristic of palm oil product .........13
2.6 Triglyceride compositions of palm oil products.........…...................................13
2.7 Typical fatty acids composition of rice bran oil. ...........................…...............18
2.8 Characteristic of refined rice bran oil .............................…..............................21
3.1 Changes in cloud point and cold test of palm olein blended with
rice bran oil. ………………………………………………………….37
4.1 Changes in color value of palm olein blended with rice bran oil
by heating method. …………………………………………………...52
4.2 Changes in color value of palm olein blended with rice bran oil
by frying method. …………………………………………………….53
IX
LIST OF FIGURES
Figure Page
2.1 Extraction of crude palm oil. ..............................…............................................5
2.2 Refining of palm oil. ......................................……............................................6
2.3 Dry fractionation process. ........................................……..................................9
2.4 Detergent fractionation process. .......................................…............................10
2.5 Solvent fractionation process. ..................…….................................................11
2.6 Palm oil utilization chart. .......................……...................................................16
2.7 Rice bran oil extraction process. .................................……..............................19
2.8 Rice bran oil refining process. ..........................……........................................20
3.1 Physical characteristic of palm olein blended with rice bran oil stored
on day 5 and day 10 ……………………………………..…………...38
3.2 Physical characteristic of palm olein blended with rice bran oil stored
on day 15 and day 20 …………………...……………………………39
3.3 Physical characteristic of palm olein blended with rice bran oil stored
on day 25 and day 30 …………………………...……………………40
4.1 Changes in overall color difference of palm olein blended with rice bran oil
in heating method. …………………………………………………...54
4.2 Changes in overall color difference of palm olein blended with rice bran oil
in frying method. …………………………………………………….55
4.3 Changes in viscosity of palm olein blended with rice bran oil in heating
method. ………………………………………………………………56
4.4 Changes in viscosity of palm olein blended with rice bran oil in frying
method. ……….……………………………………………….……..57
4.5 Changes in smoke point of palm olein blended with rice bran oil in heating
method. ………………………………………………………………58
4.6 Changes in smoke point of palm olein blended with rice bran oil in frying
method. ………………………………………………………………59
X
Figure Page
4.7 Changes in free fatty acid of palm olein blended with rice bran oil in heating
method. ………………………………………………………………60
4.8 Changes in free fatty acid of palm olein blended with rice bran oil in frying
method. ………………………………………………………………61
4.9 Changes in peroxide value of palm olein blended with rice bran oil in heating
method. ………………………………………………………………62
4.10 Changes in peroxide value of palm olein blended with rice bran oil in frying
method. ………………………………………………………………63
1
CHAPTER 1
INTRODUCTION
Frying oil is considered as the major raw material used in the frying
manufactures and its quality intimately relates to the fried product properties. Because
fat becomes an integral part of the product during the frying process, it is important to
make certainly that the fat can deliver the correct characteristics such as flavor, texture,
appearance, health, and content claims (Saguy and Dana, 2003). Thus, the frying fat
and oil commonly selected to fill into the fryers must be more able to resist the
oxidative deterioration. The oils with high saturated or monounsaturated fatty acid
contents such palm olein, peanut oil, and coconut oil can compatibly meet this
requirement. However, these oils still have a little problem in the appearance due to
the clouding formation during shelf storage. In addition, the consumers always
assumed the clouding appearance representing low quality attributes of oil although
the clouding did not detrimentally influenced the oil quality (Siew and Ng, 1996; Swe
et al., 1994).
Palm olein (PO) was the liquid fraction from palm oil in the fractionation
process. Normally, it contained about 46% saturated fatty acid and it was widely used
in frying industry due to its excellent frying performance and oxidative stability (Anon,
1991; Basiron, 1996). However, the palm olein tended to form cloud appearance and
results in the visible suspension of fat crystals normally seen in the container at the low
temperature or after long period of storage at room temperature. The fat crystals
forming in the container were normally in the β-form of saturated fatty acids and
diglycerides. The β-form of fat crystal expressed the highest melting points when
compared to others (Siew and Ng, 1996; Swe et al., 1994; Swe et al., 1995).
The several procedures were conducted to reduce the clouding problem, for
example, the application of double fractionation process, the use of crystal inhibitor,
and the oil blending technique. Double fractionation was the process applying the
Chapter 1: Introduction 2
second crystallization of palm olein to elevate iodine value above 60 (Basiron, 1996).
The crystal inhibitor was a fat-soluble products comprising of general molecule
structure similar to triglyceride but differ in some specific ways. The chemical
compounds potentially retarding the crystal growth, as the fat crystal inhibitors, for
instance, lecithin, oxystearin, and polyglycerol (Weiss, 1983). The blending of the
high unsaturated fatty acid oil, for instance, soybean oil (SBO), sunflower seed oil
(SFO), rice bran oil (RBO), and safflower seed oil (SAF) together with palm olein to
reduce the crystallization of triglyceride at low temperature was introduced by many
researchers. Mostafa et al. (1996) reported that palm olein blended with cottonseed
oils could decrease the cloud point. Teah and Ahmad (1991) investigated the mixing
oil consisting of sunflower seed oil, single fractionated palm olein, and double
fractionated palm olein was capable to inhibit the formation of fat crystals at temperate
climate.
Rice bran oil, also called rice oil was obtained from the rice milling process,
and used extensively in Asian countries (Orthoefer, 1996b). RBO normally contained
approximately 40% polyunsaturated, 40% monounsaturated, and 20% saturated fatty
acid (Orthoefer, 1996a). In addition, rice bran oil also comprised the nutritious
substance, known as a γ- oryzanol, preventing the oxidation during frying and it
contains 400 mg/kg oil of total tocotrienol (Sonntag, 1979). This substance could
retard the rate of oxidation equal to palm oil (Rossell, 2001).
Then, rice oil could be the potential oil using to blend with palm olein for
preventing fat crystals formation during oil storage. However, the blends between
palm olein and rice bran oil would change the physical and chemical characteristic
such as an increase in viscosity and color, and the reduction of the degree of
unsaturation during heating and frying similar to PO application (Moreira et al., 1988;
Orthoefer et al., 1996 White, 1991).
The objective of this study was to investigate the changes in physico-chemical
properties of the blended oil between palm olein and rice bran oil. The effect of
different blending ratio was investigated to figure out the blended oil preventing higher
thermal stability, better frying performance and appearance.
3
CHAPTER 2
LITERATURE REVIEW
2.1 Palm oil
Palm oil is derived from the mesocarp of the palm fruit, species Elaeis
guineesis. Presently, palm oil is now the second largest vegetable oil in the world
production and the leader in the world exports (Pantzaris, 1995). In generally, palm oil
had reddish brown in color due to it was high content of carotenoid, α and β carotene
about 500-700 ppm. During refining process, the β-carotene was gradually decreased.
Palm oil has a semi-solid consistency at ambient temperature, due to containing about
50% of saturated fatty acids and about 50% unsaturated fatty acids. The chain lengths
of fatty acids presented in the triglyceride comprising of a very narrow range from 12
to 20 carbon atoms (Basiron, 1996).
Sambanthamurthi et al. (2000) reported that over 95% of palm oil consisted of
the mix triglycerides containing glycerol molecules as the backbone and each of
molecule esterified with the three fatty acid. The major fatty acids in palm oil were
myristic, palmitic, stearic, oleic, and linoleic (Table 2.1). Goh (1991) reported that
two major components of triglycerides in palm oil were unsaturated-dipalmitin (C50)
and palmitounsaturated (C52) (Table 2.2). Normally C50 included palmitic-oleic-
palmitic (POP) and palmitic-palmitic-oleic (PPO), and C52 was palmitic-oleic-oleic
(POO) (Basiron, 1996). However, the triglycerides in palm oil partially exhibited the
physical characteristics of the palm oil such as melting point and crystallization
behavior (Sambanthamurthi et al., 2000).
Sambanthamurthi et al. (2000) reported that the minor constituents of palm oil
could be divided into two groups. The first group consisted of fatty acid derivatives,
such as partial glycerides (mono-and diglycerides), phosphatides, ester and sterols.
The second group included classes of compounds not related chemically to fatty acid,
such as hydrocarbons, aliphatic alcohols, free sterols, tocopherol, pigments, and trace
Chapter 2: Literature review 4
metals. Most of the minor components found in the unsaponnifiables fraction of palm
oil were sterols, higher aliphatic alcohol, pigments, and hydrocarbons. In addition,
palm oil contained mainly three types of diglyceride, C32 (dipalmitoylglycerol or PP),
C34 (palmitoyloleoylglycerol or PO), and C36 (dioleoylglycerol or OO). The
diglycerides in palm oil affected its physical property such as crystallization (Table
2.3).
Basiron (1996) reported that the extraction processes of palm oil usually began
with the fruit reception, sterilization, stripping, digestion, oil extraction, clarification,
and oil storage, respectively (Figure 2.1). Crude palm oil was extracted commercially
from the fresh fruit bunches variable amount of undesirable components and
impurities, such as mesocarp fibers, moisture and insoluble, free fatty acid,
phosphatides, trace metals, and oxidation products. As the result, palm oil was
normally refined to bland, stable product before used for consumption or formulation
of edible product (Figure 2.2).
Table 2.1 Fatty acid composition of palm oil
Weight (%)
Fatty acid Symbol Mean Range
Saturated Acids
Lauric C12:0 0.2 0.1 – 0.3
Myristic C14:0 1.1 1.0 – 1.3
Palmitic C16:0 44.7 43.9 – 46.0
Stearic C18:0 4.2 3.9 – 4.4
Arachidic C20:0 0.4 0.3 – 0.7
Mono-unsaturated Acids
Palmitoleic C16:0 0.1 0 – 0.1
Oleic C18:0 39.2 38.0 – 40.6
Poly-unsaturated Acids
Linoleic C18:2 10.0 9.2 – 10.5
Linolenic C18:3 0.3 0.3 – 0.6 Source: (Goh, 1991)
Chapter 2: Literature review 5
FRUIT RECEPTION
Fresh fruit bunches
STERILIZATION
STRIPPING
DIGESTION
OIL EXTRACTION
CLARIFICATION
CRUDE PALM OIL
STORAGE
Figure 2.1 Extraction of crude palm oil Source: (NorAini et al., 1992)
By steam in 3 horizontal sterilizers Peak pressure: 40-45 psi Time: 75-90 min
In rotary drum stripper Speed: 21-23 rpm
In steam-jacketed Cylindrical vessels with vertical Rotary shaft Temperature: 90-95oC
By screw press
At 85-95oC In settling tank
Chapter 2: Literature review 6
CRUDE PALM OIL
DEGUMMING
BLEACHING
FILTRATION
FFA DISTILLATION & DEODORIZATION
COOLING
POLISHING
REFINED, BLEACHED & DEODORIZED PALM OIL STORAGE
Figure 2.2 Refining of palm oil Source: (NorAini et al., 1992)
Phosphoric acid 0.1% Temperature: 80oC Time: 15 min /Under vacuum
Bleaching earth 1% Temperature: 95oC Time: 30 min
Temperature: 260oC Time: 1 ½-2 hr
Under vacuum
Pass through filter
Chapter 2: Literature review 7
Table 2.2 Triglyceride composition of crude palm oil
Weight (%)
Triglycerides Mean Range
C46 0.8 0.4 – 1.2
C48 7.4 4.7 – 10.8
C50 42.6 40.0 – 45.2 (POP, PPO)
C52 40.5 38.2 – 43.8 (POO)
C54 8.0 6.4 – 11.4 Source: (Goh, 1991)
Basiron (1996) reported that two methods of refining, namely physical and
chemical refinings, were available to refinie crude palm oil (Table 2.4). However,
physical refining has become the major processing route because of cost effective,
high efficiency, and simple effluent treatment. However, both processes were able to
produce refined, bleached, and deodorized (RBD) palm oil of desirable quality and
stability for edible purposes.
Chapter 2: Literature review 8
Table 2.3 Major physical properties of palm oil
Property Mean Range
Apparent density at 50oC g/ml 0.889 0.888 – 0.889
Refractive index at 50oC 1.455 1.455 – 1.456
Solid fat content (%)
At 5oC 60.5 50.7 – 68.0
At 10oC 49.6 40.0 – 55.2
At 15oC 34.7 27.2 – 39.7
At 20oC 22.5 14.7 – 27.9
At 25oC 13.5 6.5 – 18.5
At 30oC 9.2 4.5 – 14.1
At 35oC 6.6 1.8 – 11.7
At 40oC 4.0 0.0 – 7.5
At 45oC 0.7 -
Slip point (oC) 34.2 31.1 – 37.6 Source: (Sambanthamurthi et al., 2000)
The triglycerides in palm oil usually consisted of a combination of fatty acids
with different chain lengths as well as degrees of unsaturation. This resulted in the
presence of substantial quantity of both low and high melting triglycerides.
Fractionation, the crystallization of the oil under controlled cooling followed by
separation was applied to yield a low melting liquid phase (olein) and a high melting
solid phase (stearin) (Basiron, 1996).
Gunstone and Norris (1983) reported that fractionation process could be
classified to three methods, such as dry fractionation, detergent fractionation, and
solvent fractionation (Figure 2.3, 2.4, and 2.5, respectively). However, the dry
fractionation was the most widely used process. It was fully reversible modification
process, as it involved no chemical change in composition (Kellens, 1993).
Chapter 2: Literature review 9
PALM OIL
MELTING
CRYSTALLIZATION
FILTRATION
PALM OLEIN PALM STEARIN
Figure 2.3 Dry fractionation process Source: (Bernardini, 1983)
Chapter 2: Literature review 10
CRYSTALLIZATION
MIXER
FIRST CENTRIFUGATION
DETERGENT
SUSPENSION
STEARIN-DETERGENT
MELTING
OLEIN SECOND CENTRIFUGATION
STEARIN DETERGENT
Figure 2.4 Detergent fractionation process Source: (Bernardini 1983)
Chapter 2: Literature review 11
Palm oil Solvent
1st Crystallization
1st Filtration
1st Solid phase Liquid phase
2nd Crystallization
2nd Filtration
2nd Solid phase Olein phase
Distillation Distillation Distillation
Solvent
Stearin Stearin Olein
Figure 2.5 Solvent fractionation process Source: (Bernardini 1983)
Chapter 2: Literature review 12
Table 2.4 Refining crude palm oil: unit process
Stage Principal impurities reduced or removed
Degumming Phospholipids, trace metals, pigments
Neutralization Fatty acids, phospholipids, pigments, oil insoluble, water
soluble
Washing Soap
Drying Water
Bleaching Pigments, oxidation products, trace metal, traces of soap
Filtration Spent bleaching earth
Deodorization Fatty acids, mono-and diglyceride, oxidation products, pigment
Physical refining Fatty acids, mono-and diglyceride, oxidation products, pigment
Polishing Removal of trace oil insoluble Source: (Basiron, 1996)
Palm olein, was the liquid fraction obtained from fractionation of palm oil after
crystallization under controlled temperature. The physical characteristics of palm
olein differed significantly from those of palm oil. It was fully liquid in ambient
temperature (Pantzaris, 1995). However, the difference in fatty acid compositions was
also worthy, for instance, oleic and linoleic acid contents increased and the saturated
fatty acid content was lowered (Anon, 1991). Two major grades of palm olein were
produced in Malaysia, standard olein and double fractionated (or super) olein, which
has lower cloud point (Pantzaris, 1995).
PO application extended from daily usage in the kitchen toward the industrial
uses. It contained the excellent physical properties and oxidative stability for deep-
frying involving temperature over 180oC, due to vary low content of linolenic fatty
acid and combined with the naturally occurring vitamin E. Furthermore, foods fried in
palm oil and palm olein gradually absorbed less fat and tended to be less soggy than in
the case with other vegetable oils as shown in Table 2.5 and 2.6 (Anon, 1991).
Palm stearin, the solid fraction of palm oil, was characterized by a higher
melting point and a lower iodine value than those of the unfractionated oil. However,
Chapter 2: Literature review 13
during crystallization at controlled temperature, it was a co-product of palm olein.
Palm stearin was very useful source for the fully natural hard fat component used to
produce such as shortening, pastry margarine, vanaspati, etc. (Anon, 1991; Pantzaris,
1995).
Table 2.5 Fatty acids composition and physical characteristics of palm oil products
Fatty acids Palm oil Palm olein Palm stearin
C12:0 0 – 0.4 0.1 – 1.1 0.1 – 0.6
C14:0 0.6 – 1.7 0.9 – 1.4 1.1 – 1.9
C16:0 41.1 – 47.0 37.9 – 41.7 47.2 – 73.8
C16:1 0 – 0.6 0.1 – 0.4 0.05 – 0.2
C18:0 3.7 – 5.6 4.0 – 4.8 4.4 – 5.6
C18:1 38.2 – 43.5 40.7 – 43.9 15.6 – 37.0
C18:2 6.6 – 11.9 10.4 – 13.4 3.2 – 9.8
C18:3 0 – 0.5 0.1 – 0.6 0.1 – 0.6
C20:0 0 – 0.8 0.2 – 0.5 0.1 – 0.6
Iodine value 50.6 – 55.1 56.1 – 60.6 21.6 – 49.4
Slip point (oC) 32 – 39 19.4 – 23.5 44.5 – 56.2
Cloud point (oC) - 6.6 – 11.5 - Source: (Pantzaris, 1995; Tan and Flingoh, 1981)
Table 2.6 Triglyceride compositions of palm oil products
Carbon number Palm oil Palm olein Palm stearin
C46 0.4 – 1 - 0.5 – 3
C48 5 – 11 1.3 – 4.0 13 – 56
C50 40 – 45 37.7 – 45.4 34 – 50
C52 38 – 44 43.3 – 51.3 5 –37
C54 6 – 11 7.0 – 12.6 Tr – 8 Source: (Pantzaris, 1995; Tan and Flingoh, 1981)
Basiron (1996) found that the ranges of palm oil application in foods were
shortening, margarine, vanaspati, deep-frying fat, and specialty fats (Figure 2.6).
Chapter 2: Literature review 14
The contribution of palm oil to world food supplies has increased steadily in
the last 20 years and its position as a major commodity in the world trade was expected
to continue. However, consumers’ awareness of palm oil use in human nutrition was
rather low. The Malaysia Palm Oil Promotion Council has therefore invited a group of
professional scientists from a range of appropriate disciplines, to carry out an objective
review, based on an evaluation of the published information in the scientific literature
(Anon, 2000). This review is here presented as 15 facts are:
Fact 1
Palm oil is one of the sixteen edible oils processing on FAO/WHO Food
Standard under the Codex Alimentarius Commission Programme.
Fact 2
Palm oil has had a long history of food use dating back over 5,000 years.
Fact 3
Presently it is consumed worldwide as a cooking oil, in margarine and
shortening and is also incorporated into fat blends and a wide variety of food products.
Fact 4
Palm oil contains an equal proportion of saturated and unsaturated fatty acids.
Fact 5
Palm oil is prepared from the fresh palm fruit by cooking and processing only.
It should be clearly distinguished from palm kernel oil and coconut oil, because it has a
lower level of saturated components, with no significant content of capric, lauric, and
myristic acids.
Fact 6
Current food labeling regulations were classified palm oil like all other
vegetable oils, as cholesterol free.
Fact 7
For most food uses palm oil does not require hydrogenation, thus avoiding the
formation of Trans-fatty acids, and uncommon cis-fatty acids found in hydrogenated
oils.
Chapter 2: Literature review 15
Fact 8
Refined palm oil, as used in foods, is rich source of tocopherols and
tocotrienols having vitamin E activity. Unrefined palm oil is also a rich source of
carotenoids.
Fact 9
Like other common edible fats and oils, palm oil is readily digested, absorbed
and utilized as a source of energy.
Fact 10
A number of recent controlled human effect studies in Europe, USA, and Asia
have confirmed that there is no significant rise in serum total cholesterol when palm
oil, providing most of the dietary fat, is used as an alternative to other fats in the
habitual diet.
Fact 11
In the above-mentioned studies the level of HDL cholesterol, regarded as
beneficial, was unaltered or significantly enhanced.
Fact 12
The content of lipoprotein in blood plasma, a potent risk indicator of coronary
heart disease, was significantly reduced when palm oil provided most of the dietary
fat.
Fact 13
Not all saturated have the same effect on plasma cholesterol concentration.
Fact 14
Dietary palm oil performs comparably with other more unsaturated oils when
studied in a rat model of arterial thrombosis.
Fact 15
As compared with a number of other edible oils, dietary palm oil reduces the
number of chemically induced tumors in rats.
Chapter 2: Literature review 16
Figure 2.6 Palm oil utilization chart Source: (Basiron 1996)
Fresh fruit bunches
Mill process
Kernel Crude palm oil Fruit residues
Refining
Fractionation and refining Splitting
Fatty acids GlycerolRBD PO
RBD Olein RBD Stearin
Fatty alcohols, amines, amides
EmulsifiersHumectant Explosives
MargarinesShorteningsVanaspati Frying fatsIce cream
ShorteningsMargarinesVanaspati
Palm midfraction
Blending
Cocoa butter equivalent
Confectioneries
Soap
Splitting
Fatty acids
Soap Food emulsifiers
Frying Cooking
Shortenings Margarines
Chapter 2: Literature review 17
2.2 Rice bran oil Rice bran oil, also called rice oil, the by-product from rice milling. The oil has
been used extensively in Asian countries such as Japan, Korea, China, Taiwan,
Thailand, and Pakistan (Orthoefer, 1996a). Rice bran oil is generally considered to be
one of the highest quality vegetable oil available in term of its cooling qualities, shelf
life, and fatty acid composition (Hargrove, 1994).
Orthoefer (1996b) reported that the bran and polish, the source of rice bran oil
was derived from the outer layers of the rice caryopsis during milling. Rice bran oil
usually contains palmitic, oleic and linoleic fatty acids constituting more than 90% of
the fatty acid portion of the glycerides (Table 2.7). However, the major molecular
species of rice bran oil triglycerides were palmitic-linoleic-oleic, oleic-linoleic-
palmitic, palmitic-linoleic-linoleic, linoleic-linoleic-palmitic, and finally triolein.
Rice bran contains several enzymes. Lipase has been the major type enzyme
and affected the keeping quality, and the subsequent industrial usage of the rice bran.
Lipase predominately promoted hydrolysis of the oil in bran into glycerol and free
fatty acid (FFA). The rate of FFA development was quite high and directly depended
on environmental condition. FFA developed about 5-7% per day and up to 70% FFA
for a single month during storage (Orthoefer, 1996b).
Hargrove (1994) reported that there were many potentially suitable methods to
stabilize or inactivate the lipase in rice bran. Most commercial systems currently
utilized in the united state employed the moisture added or dry extrusion methods.
The bran temperature maintained at 90-100oC, after extrusion for 2-3 minutes prior to
cooling. After the extrusion stabilization, bran could be produced that would remain
stable under normal warehouse storage for maximum six months but refrigerated
storage was able to extend the shelf life significantly.
Chapter 2: Literature review 18
Table 2.7 Typical fatty acids composition of rice bran oil
Fatty Acids Weight (%)
C14:0 Tr
C16:0 16
C18:0 2
C18:1 42
C18:2 38
C18:3 1.4
C20:0 0.6 Source: (Hargrove, 1994)
Nicolosi et al. (1994) and Orthoefer (1996b) found that oil easily removed from
the bran using hydraulic pressing and/or solvent extraction (Figure 2.7). Extraction of
the oil may be carried out with a variety of solvents, although hexane is generally used.
Rice bran for solvent extraction may be steamed for stabilization and to facilitate pellet
or collate formation for higher solvent per collation rate leading to shorter extraction
time. The extraction usually may be divides into a batch type or continuous extractor.
The solvent plus oil, referred to as micella, is filtered prior to distillation of solvent.
The wet defatted bran is desolvented, dried, and cooled. The solvent is recovered
throughout the process. However, crude rice bran oil is dark greenish brown to light
yellow, depending on the condition of the bran, extraction method, and composition of
the bran.
The products of extraction may consist of defatted bran, crude rice bran oil,
wax, and soap of fatty acid. In refining process (Figure 2.8), the processes used to
preparation of food oils consist of dewaxing, the simplest technique to remove the wax
from crude rice bran oil is to use settling tanks in which the crude oil is gradually
cooled, followed by filtering or centrifuging (Orthoefer, 1996b).
Chapter 2: Literature review 19
Rice bran mill
Stabilization
Drying
Storage
Hexane extraction
Meal desolventizing Hexane distillation
Defatted meal Crude rice bran oil
Figure 2.7 Rice bran oil extraction process
Source: (Nicolosi et al., 1994)
Chapter 2: Literature review 20
Crude rice bran oil
Phosphoric acid
Water
Deguming Phospholipids
NaOH
Neutralization Fatty acid soap
Acid activated
Bleaching earth
Bleached oil
Deodorization Vegetable oil
Distillated
Rice bran oil
Figure 2.8 Rice bran oil refining process
Source: (Nicolosi et al., 1994)
Chapter 2: Literature review 21
Nicolosi et al. (1994) presented that the degumming process generally used of
degumming agents such as phosphoric or citric acid to hydrolyze at 60-80oC. The wet
gum was separated from the oil by centrifugation. Acid degumming was usually
combined with neutralization with sodium hydroxide, at temperature less than 65oC.
Free fatty acids presently were converted to sodium soaps, being hydratable and
removable by centrifugation. Bleaching of the oils was carried out to remove
pigments, oxidized lipids, and polar component from the oil. Acid activated bleaching
clay was removed by filtration. Finally, to removed of odors, flavors, and fatty acid by
steam distillation or deodorization at 220-225oC, 4-8 mmHg. The volatile compounds
including aldehydes, ketones, and peroxide could be removed from oils. After
deodorization, the rice bran oil was cooled to 10-14oC prior to storage (Table 2.8).
Table 2.8 Characteristic of refined rice bran oil
Characteristic Quality
Iodine value 99-108
Saponification value 180-190
Smoke point 213oC
Fire point 352oC
Cloud index 17oC
Refractive index 25oC 1.470 – 1.473
Specific gravity 25/25oC 0.916 – 0.921
Unsaponifiable matter 3-5%
Total tocopherol 200 mg/kg (0.02%) Source: (Hargrove, 1994)
Winterization was performed to remove the high melting triglyceride from the
fractions, the oil remained liquid at refrigeration temperature. The oils was winterized
by slowly cooling the oil to 5oC and holding for up to several days. The saturated
glyceride crystallize could be removed by filtration producing a stearin (high melting
fraction and rice oil (low melting fraction) (Nicolosi et al., 1994). The composition of
rice bran oil suggested that it could be used as a salad oil and for cooking. Therefore,
Chapter 2: Literature review 22
it had excellent oxidation stability, because it contained the natural tocopherol
(Sonntag, 1979).
Diack and Saska (1994) and Roger et al. (1993) found that fully processed rice
bran oil contained a high amount of unsaponifiable component compared to most other
vegetable oils. Two groups of components found in the unsaponifiable fraction of rice
bran have been investigated for possible health benefit, such as the tocotrienol and the
γ-oryzanol. Although, their concentrations substantially depended on the origin of the
rice bran.
Rice bran oil was used for both edible and industrial application. As only high
quality rice bran oil was used for foods. The oxidative stability of rice bran oil was
equivalent to or better than soybean, corn, canola, cottonseed, and safflower oils in
deep frying condition. Winterized rice bran oil was suitable for making mayonnaise
and salad dressing. The stearin separated during winterization could be used in
margarine and shortening application (Orthoefer, 1996b).
2.3 Blended oil The blending, mixing two or more straight or modified oils and fats, could be
the correct balance of properties such as melting point, plastic range, color, texture,
iodine value, etc (Berger, 1982). Consequently, blending was the simplest method
used to modify oils and fats for some specific applications (NorAini et al., 2001).
In tropical countries, palm olein were sold in supermarket or retail shops for
general household cooking and frying which might have a preference for a particular
flavor and taste. Palm olein could easily be blended with other oils such as groundnut
oil and sesame oil that had proved to be very popular in China as household frying
oils. The blends of palm olein with soybean oil provided oil with a balance ratio of
polyunsaturated, monounsaturated, and saturated fatty acids as recommended by some
health organizations. The new cooking oil was recently introduced in the local market
under the brand name of DAISY. This cooking was the blend of palm olein with
sunflower seed oil and canola oil (Razali and NorAini, 1994).
In Egypt, cottonseed oil was the major vegetable oil; it comprised 79.6% of the
total oil production. Recently, palm olein has been intensively used in Egypt as a
frying medias due to high oxidative stability and low price as compared to other
Chapter 2: Literature review 23
similar frying media. Blending of cottonseed oil with palm olein also improved the
frying performance (Mostafa et al., 1996). However, the palm olein was blended with
high polyunsaturated fatty acid such as SBO and SFO to increase the cold stability and
frying performance (Basoglu et al., 1996; Chu, 1991).
In 1992, Uniliver in Italy using palm olein as the main component blended with
sunflower seed oil and groundnut oil. The product was sold in Italian supermarkets
under the brand name of FRIOL. Blending of palm olein with other polyunsaturated
oil it was a good practice because the final blended oil had a better frying performance
when compared with the polyunsaturated oil alone (Razali and NorAini, 1994)
2.4 Crystallization of fats and oils Crystallization, it was necessary to increase the concentration of the solute to
be crystallized above the saturated solution concentration at a given temperature,
called supersaturated. A crystal nucleus was the smallest crystal that could exist in a
solution of a certain concentration and temperature. Aggregates of molecules smaller
than nucleus were called embryos and would redissolve if formed. When molecules
came together to form a crystal, there were two opposing forces. Firstly, energy was
evolved due to the heat of crystallization, which flavour the process. Secondly, the
surface of the crystal increased as the molecules aggregated together, called nucleation.
A crystal nucleus had formed; it would start growing by the incorporation of other
molecules, called crystal growth (Timms, 1995).
The most common types of fat crystals were the three systems such as, the
triclinic system, called beta (β). It was the most stable polymorphic form, the common
orthorhombic system, called beta prime (β′). It had intermediate stability, and the
hexagonal system, called alpha (α), the least stable polymorphism form (Newar,
1996).
Palm oil consisted of 50% saturated and 50% unsaturated fatty acids. The
major triglycerides, according to equivalent carbon number were C50 (42.58%) and
C52 (40.46%) (Cheman, 1999). The major diglyceride is C34 (54.4%), C36 (33.0%),
and C32 (12.6%). The diglyceride in palm oil affected the physical properties such as
crystallization and melting point. Also, slow down transformation of the crystals form
Chapter 2: Literature review 24
the α form to β′ form and subsequently, to the β form (Sambanthamurthi et al., 2000;
Siew and Ng, 1995; Siew and Ng, 1996a).
The major triglycerides of the olein fraction were C50 (42.04%) and C52
(45.66%). The stearin fraction consisted of C48 (22.3%), C50 (40%), and C52 (29%)
(Cheman, 1999). Palm olein tended to crystallize at low temperature. This
crystallization caused the cloud formation, sometimes observed as white sediments at
the bottom of the containing. The visual observation of these crystals was often seen
as a defect to consumers and there was no deterioration in oil quality (Siew and Ng,
1996).
Clouding was obtained after storing palm olein at 12.5oC for 12 to 24 hours and
easily separated by centrifugation. Palmitic-oleic-palmitic or POP and palmitic-oleic-
stearic or POS levels were high in the cloud material (Swe et al., 1994). The
composition of purified palm olein crystal formed at room temperature (25oC) was
identified. In addition, the major 1,3-dipalmito-glycerol was the high melting
glycerides (Swe et al., 1995). GC and HPLC analyzed the composition of the crystal
obtained during the storage of palm olein between 28oC and 10oC. The crystals were
the beta form, and consisted of high and low melting component. Although, the high
melting component mainly 1,3-dipalmitin. The mainly low melting components were
tripalmitin and dipalmitin (Siew and Ng, 1996).
Some vegetable oils form sediment or a cloudy haze during storage at room
temperature such as palm olein, canola oil, and sunflower seed oil. Among the
component implicated in turbidity formation were saturated triglyceride, waxes, free
fatty acid, hydrocarbon, sterol and their ester, and fatty alcohol (Przybylski et al.,
1993; Rivarola et al., 1985).
The higher cloud point of palm olein, compared to any other liquid oil, has
been a problem over years and partially overcome by blending, adding additives or
using a double fractionation method, but the problem still resists (Swe et al., 1994).
Chapter 2: Literature review 25
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Selangor. Palm oil Institute of Malaysia (PORIM). p 15-18.
Anon. 2000. Nutritional aspects of palm oil. In: Malaysia Palm Oil Promotion
Council, editors. An endorsement on health, nutrition, and palm Oil. Selangor.
Malaysian Palm Oil Promotion Council (MPOPC). p 33.
Basiron Y. 1996. Palm oil. In: Hui YH, editor. Bailey’s Industrial Oil and Fat
Products. Vol. 2. New York: John Wiley and Sons. p 271-375.
Basoglu FN, Wetherilt H, Pala M, Yildiz M, Biringen G, Unal M. 1996.
Improved quality of cooking and frying oils by blending palm olein. In:
World conference and exhibition on oilseed and edible oils processing. Vol 1.
Istanbul. p 159-168.
Berger KG. 1982. A LAYMAN’S glossary of oils and fats. Selangor. Palm Oil
Research Institute of Malaysia. 62 p.
Bernardini E. 1983. Vegetable oils and fats processing. Vol 2. Rome: Interstampa.
616 p.
CheMan YB, Haryaki T, Ghazali HM, Abbi BA. 1999. Composition and thermal
profile of crude palm oil and its products. J Am Oil Chem Soc 76(2):237-242.
Chu TH. 1991. A comperative study of analytical methods for evaluation of
soybean oil quality. J Am Oil Chem Soc. 68(6):379-384.
Diach A, Sasha M. 1994. Separation of vitamin E and gamma-oryzanols from
rice bran by normal phase chromatography. J Am Oil Chem Soc. 71(11):
1211-1217.
Goh EM. 1991. Palm oil compositions and quality. In: Proceeding 1991 PORIM
International Palm Oil Conference (chemistry and technology). Malaysia. p
268-278.
Gunstone FD, Norris FA. 1986. Lipids in foods: chemistry, biochemistry
and technology. Oxford: Pergamon. p 170.
Hargrove KL. 1994. Processing and utilization of rice bran in the United
States. In: Marshall WE, Wadwurth JI, editor. Rice Science and Technology.
New York: Marcel Dekker. p 381-400.
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Kellen M. 1993. New developments in the fractionation of palm oil. In: Proceeding
of the 1993 PORIM International Palm Oil Congress (chemistry and
technology). Malaysia. p 128-140.
Moreira RG, Castell-Perea ME, Barrufet MA. 1988. Deep-fat frying: fundamentals
and applications. Maryland: Aspen. 350 p.
Mostafa MM, Rady AH, Faried A, El-Egieul A. 1999. Blending of palm
olein with cottonseed oil. In: Proceeding of the 1996 PORIM International
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Nawar WW. 1996. Lipids in food chemistry. In: Fennema. OR, editor. Food
chemistry. 3rd. New York: Marcel Dekker. p 225-319.
Nicolosi RJ, Rogers EJ, Ausman LM, Orthoefer FT. 1994. Rice bran
oil and its health benefits. In: Marshall WE, Wadwurth JI, editors. Rice
Science and Technology. New York: Marcel Dekker. p 381-400.
NorAini I, Abdullahs A, Halim AH. 1992. Evaluation of palm oil quality: correlating
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NorAini I, Razzali I, Habi N, Miskandar MD, Miskadar MS, Radauan J.
2001. FTN2: Blending of palm products with other commercial oil and fats
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Orthoefer FT, Gurkin S, Koshun L. 1996. Dynamics of frying. In: Perkin EG,
Erickson MD, editors. Deep frying: chemistry, nutrition, and practical
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characterization of canola oil sediment. J Am Oil Chem Soc 70(10):1009-
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Programme. Selangor. Palm Oil Research Institute of Malaysia. p 106-117.
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29
CHAPTER 3
Resistance to Crystallization of Palm Olein Blended with
Rice Bran Oil
Abstract
The resistance to crystallization of palm olein (PO) blended with rice bran oil
(RBO) in various proportions was investigated via monitoring the changes in cold test
and cloud point during the storage. All blended oils were continuously kept at 3
different temperatures (15oC, 20oC, and room temperature; RT about 32oC).
Regarding to the cold stability test, the blends of 40% to 60% RBO kept at 20oC and
RT except at 15oC still remained visually clear after 30 days. All blends of both oils
did not pass the cold test. The cloud points of the blends significantly (p<0.05)
decreased to 5.4oC with increasing the ratio of RBO. It was observed that the addition
of RBO intensively retarded the fat crystallization and the optimum blends of both oils
(PO: RBO) was recommended as 40:60.
Keywords: crystallization, palm olein, rice bran oil, cold stability, cloud point
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 30
Introduction
Palm olein (PO) is the liquid fraction usually received from the fractionation
step in the palm oil production (Pantzaris, 1995). It is widely recommended for
cooking and frying processes in both food service institutions and industry due to its
heat stability (Anon, 1991; Basiron, 1996). As a result of containing about 46% of the
saturated fatty acid, palm olein has the tendency to crystallize at low temperature or
during long storage period at room temperature (Basiron, 1996). The changes in oil
appearance could be sometimes observed as the white crystals at the bottom of the
bottle (Siew and Ng, 1996). Swe et.al. (1994) reported that the POP and the POS
triglycerides were the major constituents in the cloud materials occurring within PO
after stored for 15-16 hours at 12.5oC. The visual observation of the fat crystals was
often notified as an important defect and misjudged by consumer (Basiron, 1996).
However, the fat crystals formation or the cloud materials of PO absolutely did not
conduct the deterioration and affected the oil quality (Siew and Ng, 1996a).
Few available procedures were explored to retard the white crystal formation at
the oil bottles, for instance, the application of double fractionation, the addition of the
crystal inhibitors, and the blending with different vegetable oils (Basiron, 1996;
Mostafa et al., 1996). The oil blending was the simplest method to modify the oil
properties for the specific application. PO was occasionally blended with other oils
containing high unsaturated fatty acid such as soybean oil, sunflower seed oil, and etc.
(Basoglu et al., 1996; NorAini et al., 2001).
In an earlier study, Teah and Ahmad (1991) reported that the blends of
sunflower seed oil (SFO) with 50% to 70% single fractionated PO would improve the
crystallization temperature down to at 10oC. In addition, they also found that a blend
of 30% double fractionated PO with 70% SFO would be suitable for climate
temperature. NorAini et al. (1992) determined the resistance to crystallization of PO
with soybean oil (SBO) at different temperatures. They reported that PO of iodine
value (IV) 65 had more ability to form fat crystals than PO IV60 or IV 63. Their study
also showed that in the applications such as salad oil, the addition of PO IV65 was able
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 31
to blend upto 30% with SBO while the use of PO IV60 or IV63 was limited to only
10% of blended oil.
Rice bran oil (RBO) was generally considered to be one of the highest quality
vegetable oils available in term of its excellent cooking quality, shelf life, and fatty
acid compositions (Hargrove, 1994). In general, it contained 40% polyunsaturated
fatty acid, 40% monounsaturated fatty acid, and 20% saturated fatty acid (Orthoefer
1996). In addition, RBO naturally consisted of the tocotrienol and γ-oryzanol to
excessively prevent the oxidation during frying at the high temperature (Sonntag,
1979).
Accordingly, this works was carried out to prepare the different blends of PO
with RBO and study their resistance to the fat crystallization as well as cold stabilities
measured by the cold test and cloud point.
Materials and Methods
The experiments were conducted with 100% single fractionation palm olein
(PO) (IV 56-58) obtained from Oleen Co., Ltd., Thailand for edible oil processing
company. The pure rice bran oil (RBO) using King brand from Thai edible oil Co.,
Ltd., Thailand were purchased from local supermarket.
Oil blending procedure
The pure PO and RBO were heated up to 60oC using hot plate (Thermolyne:
type Cimerac 2, Thermolyne Cooperation, USA) and then filtered through a Whatman
qualitative filter paper No. 4 (Whatman International Ltd., Maidstore, England). The
filtered oils were differently blended to various PO:RBO proportions (w/w) including
0:100 (pure RBO), 40:60, 45:55, 50:50, 55:45, 60:40, and finally 100:0 (pure PO).
Each of blended oil samples was filled into the 4 oz. glass bottle Regarding to NorAini
et al. (1995), all bottled oil samples were heated to 70oC for 1 hour to destroy any
crystal nuclei that might be presented using the hot air oven (Memmert, model 600,
Memmert GmbH Co.KG, Germany). The blended oils were allowed to cool to room
temperature and then covered with the plastic caps. Each of blended oil samples was
divided into two groups for further experiments.
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 32
To study the resistance to fat crystallization, the first group of the blends was
separated to store at 3 different temperatures (consisting of 15oC, 20oC and room
temperature; RT about 32oC) using the control temperature cabinets (P. Chemical Ltd.,
Thailand). Referred to the graphical methods proposed by NorAini et al. (1995), the
blends of both oils were periodically observed by visual inspection every 5 days for 30
days and graphically recorded the changes in physical properties with respect to the
crystal formation stages appearing in the container.
Cold test and Cloud point testing
The cold stability of the blends was determined using the cold test (AOCS,
method Cc 11-53) and the cloud point as described by AOCS method Cc 6-25.
The second group of blended oil samples was randomly measured the cold test
and kept in the ice bath with the control condition at 0oC for 5.5 hours to evaluate the
resistance to crystallization. This was commonly used as an index of either the
winterization of edible oil or the removal of tristearin. The oil samples must remain
clear after 5.5 hours at 0oC and was officially stated that the oil passed the cold test or
exhibited the positive response.
The cloud point was measured as the temperature at which a cloud occurring in
visual appearance was induced in the oil sample caused by the first stage of
crystallization.
Statistical analysis
All data were subjected to analyze the variance using General Linear Model
(GLM) and Least Significant Difference (LSD) at 5% confidence level was performed
to determine the difference among mean using SAS procedure (Ver. 8.1, SAS Inst.,
Cary, NC, USA).
Results and Discussion All the blended oils of PO with RBO exhibited the negative results measured
using the cold test at 0oC for 5.5 hours (Table 3.1). Therefore, all the blends and both
pure oils (including PO and RBO) could not resist the formation of fat crystals at
relatively low temperature and still not pass through the cold test since the major
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 33
composition of triglycerides and related compounds such as fatty acids and partial
glycerides were most of saturated fatty acids constituted in the single fractionated PO
(IV 56-58) and some saturated contents of RBO significantly affected the crystal
growth. Regarding to the interactions between triglycerides and diglycerides in PO,
the diglycerides were intensively able to deteriorate the PO during the crystallization.
Even though, the addition of RBO was unable to inhibit fat crystal formation, the
changes in oil compositions may attempt some benefits to improve the oil thermal
stability.
The cloud points of the blends ranged from 4.9-5.8oC (18% total difference) as
shown in Table 3.1. However, all blends containing 40 to 60% RBO remarkably
(p<0.05) decreased the cloud point as compare to 7.8oC of the pure PO. The reduction
of the cloud point may contribute upon the modification of unsaturated contents in the
blends because RBO normally contained greater unsaturated fatty acids, especially
oleic acid (C-18) up to 80%. This caused the dilution of fat crystal formation due to
lower saturated fatty acid in the blends (Orthoefer 1996). Few researchers had studies
the blends of oil containing greater unsaturated fatty acid oil such as SBO with low-
erucic acid rapeseed oil (LEAR) and reported the same results (NorAini et al., 1992;
NorAini et al., 1995).
Higher cloud point of PO as compared to any other liquid oils has continuously
been a visual problem over the years and has overcome by blending with unsaturated
oils, adding additives or using a double fractionation (Swe et. al., 1994). Thus, the
resistance to crystallization of single fractionated PO blended with RBO was strongly
recommended to solve this problem. At 15oC, the blends (PO:RBO) in all interested
proportions except the pure RBO continued forming the fat crystals at the bottom of
the containers after 5 days of storage and substantially developed abundant fat crystals
that would result in the final semisolid within 30 days. However, the pure (100%)
RBO also first formed the clouding point at 10 days (Figure 3.1a). The crystallization
of the blends was usually accelerated with high proportions of PO at the low
temperature since the single fractionated PO comprised high-saturated fatty acid.
Several researches indicated that the fat crystallization was generated with respect to
the early nucleation of some certain high melting glycerides (Swe et al., 1994; Swe et
al., 1995). According to several studies, they found that the major components causing
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 34
the clouding of PO were POP, POS, and diglycerides particularly 1,3 PP (Siew and
Ng, 1996a; Siew, 2002; Swe et al., 1994; Swe et al., 1995). After 10-15 days of
storage at 15oC, the oil samples created some tiny particles at the bottom and the pure
PO was entirely solidified as shown in the Figure 3.1b-3.2a. On 20 days, the blends
with 50% and 60% PO developed the semi-solid whileas the blends with 45% PO was
visually observed to be only cloudy (Figure 3.2b). At 30 days, all oil samples with
high PO completely set to solid state only except the pure RBO and the blend in
proportions PO:RBO (40:60) still displayed the tiny particle (Figure 3.3b). In general,
the crystallization behavior of the blended oils based on the polymorphism of fat and
the nucleation of triglyceride crystals gradually formed after long period of storage
(Siew and Ng, 1996a; Siew and Ng, 1996b; Siew and Ng, 1996c; Swe et al., 1995).
Therefore, the removal or inhibition of the crystals formation would be essential to
improve the oil quality and appearance.
At 20oC and RT, all the blends and the pure oils existed completely clear
throughout 30 days (Figure 3.1-3.3) due to high temperature storage. In general, the
pure PO was completely clear at temperature between 22-25oC but exhibited
cloudiness and sedimentation at low temperature (Siew, 2002). Regarding to this
experiment, the blends of PO with RBO kept at 20oC and RT significantly impeded the
fat crystallization and was capable to achieve the persistent problem of PO during the
distribution in the oil market.
Conclusions All various blends of PO with RBO were unable to retard the fat crystal
formation at relatively low temperature (at 0oC, 5.5 hours) and still not pass through
the cold test. The cloud points of the blends ranged from 4.9-5.8oC and remarkably
(p<0.05) decreased with greater %RBO addition. The blends of PO with various
proportions (40% to 60%) of RBO extensively resisted the fat crystallization and still
remained transparently clear during 30 days of storage at 20oC and RT. In contrast,
the blends kept at 15oC could not prevent the clouding formation due to the hard
melting triglycerides crystals. Therefore, the blends of both oils could be the potential
future product utilized in the food manufacturing.
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 35
References Anon. 1991. Palm oil in the diet. In: Palm oil and human nutrition. Selangor. Palm
Oil Institute of Malaysia (PORIM). p 15-18.
Basoglu FN, Wetherilt H, Pala M, Yildiz M, Biringen G, Unal M. 1996.
Improved quality of cooking and frying oil by blending palm olein. In: Word
Conference and Exhibition on Oilseed and Edible Oils Processing. Vol 1.
Istanbul. p 159-168.
Basiron Y. 1996. Palm oil. In: Hui YH, editor. Bailey’s Industrial Oil and Fat
Products. Vol 2. New York: John Wiley and Sons. p 271-375.
Hargrove KL Jr. 1994. Processing and utilization of rice bran in the United
States. In: Marshall WE, Wadwurth JI, editors. Rice Science and Technology.
New York: Marcel Dekker. p 381-400.
Mostafa MM, Rady AH, Faried A, El-Egieul A. 1999. Blending of palm olein with
cottonseed oil. In: Proceeding of the 1996 PORIM International Palm Oil
Congress, (chemistry and technology). Malaysia. p 286-300.
NorAini I, Razzali I, Habi N, Miskandar MD, Miskadar MS, Radauan J. 2001. FTN2:
Blending of palm products with other commercial oil and fats for food
applications. In: 2001 PIPOC International Palm Oil Congress Food
Tecnology and Nutrition Conference. Malaysia. p 13-22.
NorAini I, Hanirah H, Flinguh CH Oh, Sudin N. 1992. Resistance of crystallization
of blends of palm olein with soybean oil stored at various temperatures. J Am
Oil Chem Soc 69(12):1206-1209.
NorAini I, Hanirah H, Sudin N, Flingoh CH SH, Tang TS. 1995. Clarity of blends of
double-fractionated palm olein with low-erucic acid rapeseed oil. J Am Oil
Chem Soc 72:443-448.
Orthoefer FT. 1996a. Rice bran oil: healthy lipid source. Food Technol 50(12):62-64.
Pantzaris TP. 1995. Pocket book of palm oil uses. Palm Oil Research Institute of
Malaysia. Kaula Lumphur. Malaysia. 158 p.
Siew WL, Ng WL. 1996a. Characterization of crystals in palm olein. J Sci
Food Agri 70:212-216.
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 36
Siew WL, Ng WL. 1996b. Effect of diglycerdes on the crystallization of palm
olein. J Sci Food Agri 71:496-500.
Siew WL, Ng WL. 1996c. Crystallization behavior of palm oleins. Elaeis 8(2):75-82
Siew W L. 2002. Understanding the inter actions of diacylglycerols with oils for
better product performance. Palm Oil Dev 36:6-12.
Sonntag NOV. 1979. Composition and characteristics of individual fats and oils:
rice bran oil. In: Swern D, editor. Bailey’s Industrial oil and fat products
Vol 1. 4th ed. New York: Wiley and Sons. p 407-409.
Swe PZ, CheMan YB, Ghazali HM. 1995. Composition of crystals of palm olein
formed at room temperature. J Am Oil Chem Soc 72(3):343-347.
Swe PZ, CheMan YB, Ghazali HM, Wei LS. 1994. Identification of major
triglyceride causing the clouding of palm olein. J Am Oil Chem Soc
71(10):1141-1144.
Teah YK, Ahmad I. 1991. Palm olein improves cooking oil blends. Palm Oil Dev.
15:2-8.
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 37
Table 3.1 Changes in cloud points and cold test of PO blended with RBO
Ratio Cloud points Cold test*
PO:RBO (oC) (0oC; 5.5 hour.)
0:100 4.0±0.1 Negative
40:60 4.9±0.2 Negative
45:55 5.0±0.3 Negative
50:50 5.3±0.1 Negative
55:45 5.5±0.1 Negative
60:40 5.8±0.4 Negative
100:0 7.8±0.4 Negative
* Negative: Did not pass through cold test according to AOCS Cc 11-53
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 38
(a)
(b)
RT = room temperature
Figure 3.1 Physical characteristic of palm olein blended with rice bran oil stored at
various temperatures on day 5 and day 10.
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 39
(a)
(b)
RT = room temperature
Figure 3.2 Physical characteristic of palm olein blended with rice bran oil stored at
various temperatures on day 15 and day 20.
Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 40
(a)
(b)
RT = room temperature
Figure 3.3 Physical characteristic of palm olein blended with rice bran oil stored at
various temperatures on day 25 and day 30.
41
CHAPTER 4
Thermal Stability of Palm Olein Blended with Rice Bran Oil
Abstract
The frying performance of palm olein (PO) blended with rice bran oil (RBO) in
various proportions was evaluated by means of monitoring their chemical and physical
changes over 40 hours of heating and intermittent frying of potato chips. Regarding to
official oil quality indexes, free fatty acid content (%FFA), peroxide value (PV),
viscosity, and overall color difference (∆E) of all blends intensively elevated (p<0.05)
with longer time due to the deteriorative process. In contrast, the smoke point
adversely decreased (p<0.05). The additional RBO in PO remarkably displayed
(p<0.05) better thermal stability and frying performance with respect to its naturally
abundance of γ-oryzanol and tocotrienols. The blends of both oils beneficially
improved (p<0.05) the oxidative stability. Conclusively, the most appropriate
PO:RBO ratio probably was 50:50. After 40 hours of heating, the viscosity, %FFA,
and PV of the blends at 50:50 were relatively lower by 5.1%, 36.5%, and 4.2%
respectively, and the smoke points exhibited notably higher (1.69%) than the ones in
100% PO.
Keywords: thermal stability, palm olein, rice bran oil, blended oils, deterioration
Chapter 4: Thermal stability of palm olein blended with rice bran oil 42
Introduction
During the deep fat frying, the frying oils used continuously or repeatedly at
high temperatures in the presence of oxygen and water from the wet foods, were
abused via thermal oxidation, polymerization, and hydrolysis. The resultant
decomposition products adversely affected the flavor and color of both fried products
and oil (Clark and Serbia, 1991; White, 1991). Thus, the thermal stability and frying
performance of frying oil normally be considered as one of the most criteria to
appropriately select the types of oil used in the frying process (Fauziah et al., 2000).
In addition, the customers regularly bought the oil with respect to its nutritional value,
availability, price, flavor, and stability during storage (Mostafa et al., 1996). Thus, the
excellent frying oil must perform the excellent ability in oxidative stability, flavor
stability, taste, nutritional values (Xu et al., 1999).
Normally, the frying manufacturers substantially utilized palm olein (PO) as a
frying medium due to its unique chemical compositions and good oxidative stability
(Teah and Ong, 1988; Mostafa et al., 1996). PO, the liquid fraction of palm oil,
normally comprised largely of 46% of saturated, 43% of monounsaturated, and 11% of
unsaturated fatty acids (Sambanthamurthi, 2000). In addition, PO was remarkably
composed of about 1000 ppm of vitamin E and one-third of which were tocopherols
and two-third were the unsaturated analogues, tocotrienols (Mostafa et al., 1996).
These abundant substances have been demonstrated to display better cooking and
frying performance than most of the liquid vegetable oils.
As a result of high-saturated content, PO consequently solidified and partially
formed visually cloudy suspension of fat crystals normally seen in the container after
long storage at room temperature (Siew and Ng, 1996a). Consumers usually
associated clouding with low quality cooking oil since they required the cooking oil
remaining clear and transparent at room or lower temperature storage. This has been
limited the shelf storage during distribution. It has been well known that blending of
PO with high-unsaturated content such as RBO or SFO may improve the physico-
chemical properties and stability (NorAini et al., 2001; Yoon et al., 1987). In fact,
extensive quantities of blended oils presently are used for cooking, frying and
manufacturing of salad dressings.
Chapter 4: Thermal stability of palm olein blended with rice bran oil 43
Rice bran oil (RBO), also called rice oil, remarkably possesses the excellent
frying performance, good stability and also contributes a pleasant flavor to the fried
food (Maccaskill and Zhang, 1999). Normally, RBO contains approximately 40%
polyunsaturated, 40% monounsaturated, and 20% saturated fatty acid, and higher
concentration of unsaponifiables such as γ-oryzanol and tocotrienols. RBO presently
is one of the most important qualities of cooking oil used extensively in Asian
countries (Orthoefer, 1996). Haumann (1996) reported that the ideal frying oil would
be a low saturated, ultra high oleic (90% or greater) and very low linolenic (less than
0.5%) fatty acid contents.
Several studies (Kochhar, 2000; Haumann, 1996) found that the stable and
healthful frying oil was commercially formulated under brand Good Fry Oil containing
the main component of high-oleic sunflower seed oils. Its excellent oxidative and
flavor stabilities dealing with the additional small portion of sesame seed oil and rice
bran oil were substantially beneficial effects to use as industrial frying and cooking oil.
Basoglu et al. (1996) determined the frying performance of the double-fractionated
palm olein (IV 60) blended with sunflower seed oil (SFO) and soybean oil (SBO) and
indicated that the blends effectively improved better frying performance than the pure
ones. The addition of SFO and SBO in PO achieved to gradually darken the oil color,
increase free fatty acid content, and decrease the smoke point. Mostafa et al. (1996)
also reported that the blends of PO with cottonseed oil dramatically improved the
oxidative stability and prolonged shelf life of the fried products.
The objectives of this study were conducted to examine the changes in physical
and chemical properties of various blends of PO with different RBO with respect to
heating and frying tests and to evaluate the optimum ratio of the blended oil providing
better performance as a frying medium or cooking oil.
Materials and Methods The experiments were conducted with 100% single fractionation palm olein
(IV 56-58) obtained from Oleen Co., Ltd., Thailand for edible oil processing company.
The pure rice bran oil (RBO) using King brand from Thai edible oil Co., Ltd.,
Thailand were purchased from local supermarket.
Chapter 4: Thermal stability of palm olein blended with rice bran oil 44
Oil blending preparation
The PO and RBO were heated up to 60oC using hot plate (Thermolyne: type
Cimerac 2, Thermolyne Cooperation, USA) and then filtered through a Whatman
qualitative filter paper No. 4 (Whatman International Ltd., Maidstore, England). The
filtered oils were differently blended to various PO:RBO proportions (w/w) including
0:100 (pure RBO), 40:60, 45:55, 50:50, 55:45, 60:40, and finally 100:0 (pure PO).
The prepared blends were used in further heating and frying tests.
Heating experiment
A 900 ml of blended oil was subjected to continuous heating process at 180oC
using an electrical hot plate (Thermolyne: type Cimarec 2, model 46920-26,
Burnshead/ Thermolyne Cooperation, USA) for 40 hours. The heating schedule was
run for 5 days, and 8 hours per day. Approximate 100 g of treated oil was randomly
taken periodically after 8, 16, 24, 32, and 40 hours, respectively and then kept in the
cold storage at 4oC before further physical and chemical analyses. During heating test,
no fresh oil was added into the vessel to maintain the oil level. All experiments were
performed in triplicate.
Frying experiment
The fresh potatoes purchased from the local supermarket were washed with
soft water at room temperature, peeled, and then sliced to thickness of 2 mm. All
sliced potatoes were immediately kept in plastic bags for frying experiment.
A 3000 g of each blended oil (PO and RBO) was heated in a batch deep fat
fryer (Princess, model 2627WA, Princess Household Applied Co., Ltd, Netherlands).
A 100 g of the slices was fried in the batch fryer at 180oC for 2 min. The frying cycle
was every 20 min and twenty-four batches of the sliced potatoes were continuously
fried daily (8 hours/day) for 5 days. At the end of daily frying operation, the fryer was
switched off and the oil temperature was allowed to equilibrate to room temperature
for overnight and then reheated in the next frying day.
A 100 g of oil sample was periodically withdrawn at 8, 16, 24, 32, and 40
hours, respectively, and then kept at 4oC before the further analyses. Fresh oil was not
added to the frying vessel until the experiment was finished.
Chapter 4: Thermal stability of palm olein blended with rice bran oil 45
Physical analysis
The changes in oil color were measured using Electric Lovibond Tintometer
model PFX190 covet 10-mm observer 2o illuminant D65 (The Tintometer Co., Ltd.,
England). The measurements were displayed in the unit of CIE (1976) system: L*
(lightness-darkness), a* (red-green), and b*(yellow-blue). The overall color difference
(∆E) was calculated to represent the color development because of thermally
detrimental oil.
The viscosity was measured using Brookfield viscometer model LVF100
(Brookfield Engineering Laboratories, Inc., USA) at 30oC, speed 50 rpm with the disk
spindle No.LV-2. The inclination of smoke point was estimated according to AOCS
Cc 9a-48.
Chemical analysis
The percentage of free fatty acid (%FFA) expressed as oleic acid content was
determined by alkaline titration according to AOCS Ca 5a-40. The peroxide value
(PV) was measured according to AOCS Cd 1-53.
Statistical analysis
All the data were subjected to analysis of variance using General Linear Model
(GLM) and Least Significant Difference (LSD) at 5% confidence level was performed
to discriminate the difference among means of PO:RBO proportions using SAS
procedure (Ver. 8.1, SAS Inst., Cary, NC, USA).
Results and Discussion Color Development of the blended oils (PO:RBO)
Generally, the fresh PO exhibited redder than the pure RBO with respect to
higher a* value of -6.0 and -7.6, respectively (Table 4.1). PO normally was known to
have a somewhat higher orange-red color as compared with the polyunsaturated oils
such as rice bran oil (RBO) and soybean oil (SO). This was an inherent property of
palm containing carotenoid pigments approximately 500-700 ppm (Basoglu et al.,
1996; Basiron, 1996). Several researches were explored the carotenoid compounds
Chapter 4: Thermal stability of palm olein blended with rice bran oil 46
that usually comprised most of α-carotene and β-carotene accounting for 90% of the
total catotenoids and the remaining substances included phytoene, lycopene, and
neurosporene (Basoglu et al., 1996; Sambanthamurthi et al., 2000). In the oil
manufacturing, the fresh PO was regularly measured as red and yellow units using
Lovibond instrument and was about 1 of redness and 7.2 of yellowness as compared
with SBO which showed 0.5 of redness and 3.3 of yellowness (Basoglu et al., 1996).
Thus, the pure PO color was normally darker than RBO in nature. Consequently, the
blending PO with RBO could improve the color of the blended oil due to the dilution
effect. During heating, both PO and RBO underwent (p<0.05) darker, redder, and
more yellow with longer time. As expected, all blends at every ratio progressively
impeded the rate of color changes, especially, in redness up to 16 hours of heating. In
frying experiment, there was not difference in overall color among the blends and the
pure ones (Table 4.2).
The overall color difference (∆E) of all blends increased up to 70% and 50%,
respectively, in heating and frying over 40 hours as shown in Figure 4.1-4.2. In
general, the heated oil intensively darkened during heating and frying due to its
degradation and oxidative reactions. The oxidized products subsequently breaking
down and generating a great variety of hydrocarbons and polymers resulted in the
darker color development. The color substances could dissolve in frying oil and make
the oil seem deterious (CheMan et al., 2003; Stevenson et al. 1984; Xu et al. 1999).
With a somewhat higher in red color, PO would start darkening at faster rate
than polyunsaturated RBO. However, this did not significant affect the color of the
fried potato. Thus, color alone was not conclusive in describing the oxidation state of
the oil. In addition, the blends with PO and RBO still contained the much more natural
antioxidants providing the great beneficial effect to prevent the oil deterioration.
Changes in viscosity
The viscosity of all blended oil samples gradually increased (p<0.5) over 40
hours during heating and frying tests (Figure 4.3-4.4). In general, the viscosity of all
blends and both pure oils tended to increase because of their oxidation and
polymerization. This could be explained by the formation of polymer compounds and
the tendency toward forming during heating and frying (CheMan et al., 2003). As
Chapter 4: Thermal stability of palm olein blended with rice bran oil 47
expected, the viscosity of RBO showed significantly higher than PO as compared to
the same periods of thermal processes. For example, after 40 hour of heating and
frying tests, the viscosity of RBO was measured as 100.5 cp and 101 cp, respectively,
which was greater than PO about 13.6% and 23.2%, respectively. Regarding to the
difference in fatty acid compositions, RBO naturally comprised most of substantially
higher unsaturated fatty acids such as linoleic acids and oleic acids tended to be rapidly
oxidized and form polymer compounds, for instance, dimmers, trimers, and tetramers
(Bracco et al., 1981). In contrast, PO normally contained largely of 46% of saturated,
43% of monounsaturated, and 11% of unsaturated fatty acids (Sambanthamurthi,
2000). While oxidation of saturated fatty acids generally produced various
hydrocarbons, carbonyls, and ketones, these products directly promoted the dark color
development but did not really affect the viscosity. The increase in viscosity of each
blend at various RBO proportions was obvious and fluctuated among themselves.
However, the lowest viscosity of the blends (PO:RBO) was in wide ranges of 45:55
and 50:50, respectively.
Thermal effects on smoke point
Normally, the frying oil would be considered to discard when its smoke points
was less than 170oC because of an excessive smoke formation in the environment and
health hazard concerns. The smoke points of all oil samples gradually decreased
during heating and frying over 40 hours due to the consequence of an increased in
polar components and the accumulation of low molecular weight decomposition
(LMWD) products (Augustin et al., 1987; Yoon et al., 1987). As expected, RBO
exhibited better physical resistance to decline the smoke points since it contain with
high-unsaturated contents as compared to the pure PO. After heating for 40 hours, the
smoke points of RBO and PO were 186oC and 176.7oC, respectively. It seemed that
RBO intensively resisted breaking down its constituents more superior (approximately
5.3%) than PO. In the end of frying experiment, the use of PO as frying medium
might be unacceptable with regard to lower smoke point than the industrial regulations
(as seen about 169.7oC). Thus, the blending PO with RBO provided the great
advantage to prolong the frying oil life in the fryer. In addition, the smoke points of all
blends in frying experiment were significantly lower than in heating test because the
Chapter 4: Thermal stability of palm olein blended with rice bran oil 48
majority of reactions took place in the hot oil was pyrolysis and oxidative degradation
and resulted in the accumulation of LMWD products such as carbonyls, hydrocarbons,
and partial glycerides. These results agreed with Basoglu et al. (1996) that attempted
to blend SBO and SFO with PO.
Deteriorative Stability of blends (PO:RBO)
Free fatty acid formation presently is the most important chemical index used
to decide the state of oil deterioration since it is very simple alkaline titration and cost
effective. Thus, almost the fried food manufacturers have been applied to monitor the
frying oil quality. The fresh and the blends used in both heating and frying all had
FFA contents below 0.12%. The FFA contents of all blends substantially increased
(p<0.05) as shown in Figure 4.7-4.8 due to hydrolysis and thermal cleavage. The fresh
PO displayed slightly higher value than the fresh RBO. Yoon et al. (1987) reported
that FFA of the fresh RBO used in their experiment was about 0.17 and finally reached
0.64 after 50 hours of heating, whereas that of double fractionated (DF) PO increased
from 0.23 to 1.30 in the same period and they also proposed that DFPO had a higher
free fatty acid than RBO. The FFA content from frying test was higher than heating
test since the moist foods regularly were fried and then existed the evaporation of
liquid water from foods to the hot oil (CheMan et al., 2003; Pantzaris, 1999). This
promoted the rapid rate of hydrolysis of triglycerides in the frying oil. Regarding to
the USDA regulations, it usually limited the FFA content not excess more than 2% in
meat products and 1% in fried snack foods. Thus, the suitable blending PO with RBO
at 50:50 notably employed to use for the fried food application.
The FFA of PO higher than RBO in both heating and frying because the
decomposition of the secondary oxidation products was created as peroxide value
(Figure 4.9-4.10). The FFA content of the PO: RBO proportions of 50:50 were the
lowest.
Peroxide value (PV) in all oil samples relatively increased within the 8 hour of
heating and frying and subsequently represented the constant tendency until 32 hour of
both heating and frying but suddenly sharp dropped after 40 hrs (Figure 4.9-4.10).
However, the differences in PV of all oils were not found (p>0.05). In addition, PV of
fresh PO was considerably higher (p<0.05) than that of RBO in the frying test.
Chapter 4: Thermal stability of palm olein blended with rice bran oil 49
Although, fresh PO naturally contains a great variety of abundant (about 500-700 ppm)
carotenoids such as tocotrienols, α-carotene, β-carotene, and lycopene, acting as a
source of antioxidants, these substances were relatively uncompatible with the
excellent antioxidative efficiency of γ-oryzanol and tocotrienols in RBO (Basoglu et
al., 1996; Sambanthamurthi et al., 2000). In general, peroxide molecules initially
formed were highly unstable and reacted quickly to form secondary oxidation products
(CheMan et al., 2003). As a result of PV measurement, the blending PO with RBO
provided the sufficient ability to suppress the peroxide formation during frying process
and the blend at 50:50 exhibited the best ability to prevent the peroxide formation.
Conclusively, the blended oil between PO and RBO at ratio of 50:50 was the most
appropriate blended oil to utilize as a new trend of cooking oil due to remarkable
thermal and oxidative stability.
Conclusions
The blending PO with RBO predominantly provided the synergistic ability to
retard the thermal and oxidative reactions during thermal process since the blends
represented better thermal stability and frying performance than the fresh ones. The
most appropriate ratio of the blended oil was 50:50 due to its ability to lower both FFA
content and PV by 57.4%, 4.42% in heating test and 46.7%, 131% in frying
experiments, respectively.
Chapter 4: Thermal stability of palm olein blended with rice bran oil 50
References Augustin MA, Asap T, Heng LK. 1987. Relationships between measurements of fat
deterioration during heating and frying in RBD. Olein. J AmOil Chem Soc
64(12):1670-1675.
Basoglu FN, Wetherilt H, Pala M, Yildiz M, Biringen G, Unal M. 1996.
Improved quality of cooking and frying oil by blending palm olein. In: World
Conference and Exhibition on Oilseed and Edible oils Processing. Vol 1.
Istanbul. p 159-168.
CheMan YB, Ammawath W, Rahman RA, Yusof S. 2003. Quality characteristic of
refined, bleached and deodorized palm olein and banana chips after deep-fat
frying. J Sci Food Agri 83:395-401.
Clark WL, Serbia GW. 1991. Safety aspects of frying fats and oils. Food Technol
46(2):81-89,94.
Fauziah A, Razali I, NorAini S. 2000. Frying performance of palm olein and
high oleic sunflower oil during batch frying of potato crisp. Palm Oil Dev. 33:
1-7.
Haumann BF. 1996. Frying fats (The goal: tastier and healthier fried foods).
INFORM 7(4):320-333.
Kochhar SF. 2000. Stable and healthful frying oil for the 21st century. INFORM
11(6):642-647.
Melton SL, Jafar S, Sykes D, Trigiana MK. 1994. Review of stability measurements
for frying oils and fried food flavour. J Am Oil Chem Soc 71(12):1301-1308.
Mccaskill DE, Zhang F. 1999. Use of rice bran oil in foods. Food Technol. 53(2):
50-52.
Mostafa MM, Rady AH, Faried A, El-Egieul A. 1996. Blending of palm olein with
cottonseed oil. In: Proceeding of the 1996 PORIM International Palm Oil
Congress (Chemistry and Technology). Palm Oil Research Institute of
Malaysia (PORIM). p 280-300.
NorAini I, Razali I, Habi N, Miskandar MD, Miskandar MS, Radzuan J. 2001.
FTN2: Blending of palm olein products with other commercial oils and fats
Chapter 4: Thermal stability of palm olein blended with rice bran oil 51
for food application. In: 2001 PIPOC International Palm Oil Congress Food
Technology and Nutrition Conference. Malaysia. p 13-22.
Orthoefer FT. 1996a. Rice bran oil: healthy lipid source. Food Technol 50(2):62-64.
Pantzaris TP. 1999. Palm oil in frying. In: Bosku and Elmadfa, editors. Frying of
food: oxidation, nutrient and non nutrient, antioxidant, biologically, active
compounds and high temperature. Basel: Technomic Publishing. p 223-252.
Saguy I.S, Dana D. 2003. Integrated approach to deep fat frying: engineering
nutrition, health and consumer aspect. J Food Eng 56:143-152.
Sambanthamurthi MR, Sundran K, Tan YA. 2000. Chemistry and biochemistry of
palm oil. Prog Lipid Res 39:507-558.
Siew WL, Ng WL. 1996a. Characterization of crystals in palm olein. J Sci Food Agri
70:212-216.
Stevenson SG, Vaisey-Gensen M, Eskin NAM. 1984. Quality control in the use of
deep frying oils. J Am Oil Chem Soc 61(6):1102-1108
Teah YK, Ong ASH. 1988. Palm oil-an excellent frying medium in food science and
technology in industrial development. In: Proceeding of the Food Conference.
Bangkok. p 417-420.
Xu XQ, Tran VH, Palmer M, White K, Salisbury P. 1999. Chemical and physical
analyses and sensory evaluation of six deep-frying oils. J Am Oil Chem Soc
76(9):1091-1099.
Yoon SH, Kim SK, Kim KH, Kwon TW, Teah YK. 1987. Evaluation of
physicochemical changes in cooking oil during heating. J Am Oil Chem
Soc 64(6):870-873.
White PJ. 1991. Methods for measuring changes in deep-fat frying oils. Food Technol
46(2):76-80.
Chapter 4: Thermal stability of palm olein blended with rice bran oil 52
Table 4.1. Changes in color value of palm olein blended with rice bran oil by heating
method
Scale Tim
e
100PO 100RBO 40PO: 45PO: 50PO: 55PO: 60PO:
Valu
e
(hrs) 60RBO 55RBO 50RBO 45RBO 40RBO
L* 0 93.2±0.
7
94.4±0.
1
95.2±0.
1
88.1±0.
5
92.0±3.
4
94.9±0.
2
94.3±0.
6
8 91.2±0.
3
94.1±0.
1
94.0±0.
1
85.7±0.
7
90.1±4.
0
93.7±0.
1
93.0±0.
8
16 90.9±0.
1
92.7±0.
4
92.6±0.
1
83.7±0.
7
88.3±3.
7
92.6±0.
1
92.2±0.
6
24 89.8±0.
4
91.5±0.
6
91.4±0.
2
81.2±0.
7
86.8±3.
9
91.5±0.
3
91.4±0.
2
32 88.4±0.
4
89.8±0.
6
89.4±0.
4
79.3±3.
6
86.4±0.
7
89.8±0.
6
89.7±0.
6
40 86.0±0.
7
87.7±0.
3
86.8±0.
3
75.0±0.
5
82.4±2.
0
87.5±0.
3
87.2±0.
8
a* 0 -6.0±0.1 -7.6±2.6 -6.4±0.3 -6.7±0.2 -6.4±0.2 -6.5±0.2 -6.4±0.1
8 -7.1±0.1 -7.1±0.6 -7.5±0.1 -8.5±0.1 -7.8±0.5 -7.3±0.1 -7.2±0.3
16 -8.3±0.2 -8.6±0.3 -9.0±0.1 -8.2±0.4 -8.4±0.2 -8.9±0.1 -8.8±0.2
24 -8.4±0.1 -9.5±0.3 -9.2±0.1 -6.6±0.5 -7.9±0.7 -9.2±0.2 -9.3±0.1
32 -7.0±0.4 -8.7±0.5 -7.1±0.3 -5.2±0.6 -3.4±1.7 -7.8±0.5 -8.0±0.4
40 -3.6±0.5 -5.6±0.3 -2.7±0.3 -1.7±1.1 -0.5±0.3 -4.7±0.3 -4.3±1.1
b* 0 21.7±1.
3
23.3±6.
4
20.2±0.
3
18.8±0.
1
20.0±1.
1
20.3±0.
1
20.2±0.
3
8 36.5±2.
7
23.7±1.
0
29.8±0.
6
38.2±1.
0
35.5±1.
7
30.4±0.
6
30.4±0.
9
16 43.9±2. 33.5±2. 42.3±1. 55.5±1. 51.3±1. 42.5±0. 41.1±0.
Chapter 4: Thermal stability of palm olein blended with rice bran oil 53
0 1 1 1 3 9 6
24 53.0±2.
7
45.1±2.
9
53.9±0.
6
69.8±1.
0
59.0±6.
2
52.6±2.
0
50.5±0.
5
32 64.4±1.
0
58.4±1.
8
67.1±0.
5
83.3±5.
5
77.6±5.
3
64.4±1.
5
62.5±0.
9
40 74.1±1.
1
70.4±0.
4
78.5±1.
0
89.9±6.
8
87.7±5.
9
74.5±0.
4
74.5±2.
0 n = 9
Chapter 4: Thermal stability of palm olein blended with rice bran oil 54
Table 4.2. Changes in color value of palm olein blended with rice bran oil by frying
method
Scal
e
Tim
e
100PO 100RBO 40PO: 45PO: 50PO: 55PO: 60PO:
valu
e
(hrs) 60RBO 55RBO 50RBO 45RBO 40RBO
L* 0 93.9±0.
3
94.0±0.
7
94.5±0.
2
94.7±0.
4
94.8±0.
4
94.3±0.
3
94.3±0.
8
8 93.0±0.
4
93.4±0.
9
93.0±0.
3
92.2±0.
4
92.4±0.
1
92.0±0.
4
92.5±0.
8
16 92.7±0.
6
92.2±0.
6
91.9±0.
3
91.1±0.
5
91.3±0.
6
90.9±0.
4
91.8±0.
6
24 92.1±0.
6
91.6±0.
6
91.2±0.
3
90.1±0.
5
90.2±0.
9
90.3±0.
6
90.8±0.
5
32 91.5±0.
3
89.7±1.
2
89.7±0.
3
88.9±0.
6
87.5±1.
0
88.9±1.
1
89.2±1.
0
40 89.7±1.
2
88.5±1.
5
87.2±0.
5
87.1±0.
9
85.9±1.
1
86.5±1.
4
87.1±1.
2
a* 0 -6.0±0.1 -6.4±1.9 -5.9±0.7 -6.2±0.5 -6.1±0.5 -6.0±0.5 -6.1±0.4
8 -7.2±0.2 -7.2±0.4 -6.8±0.2 -7.2±0.4 -7.1±0.5 -6.7±0.1 -6.7±0.2
16 -8.0±0.2 -8.0±0.2 -7.7±0.2 -8.2±0.5 -8.2±0.8 -7.5±0.2 -7.5±0.3
24 -8.6±0.1 -8.7±0.4 -8.3±0.2 -8.6±0.6 -8.6±0.9 -8.0±0.1 -8.1±0.3
32 -9.2±0.2 -8.8±0.3 -8.2±0.2 -8.1±0.8 -7.9±0.8 -7.8±0.8 -8.2±0.3
40 -8.9±0.5 -8.5±0.5 -6.4±0.3 -6.6±1.4 -5.9±1.0 -5.9±1.7 -6.6±0.9
b* 0 20.7±1.
0
21.4±4.
7
19.5±1.
5
20.3±1.
3
20.1±2.
1
20.0±0.
2
19.9±0.
1
8 29.7±2.
6
26.3±1.
6
28.7±1.
6
33.3±2.
3
33.5±2.
9
31.0±2.
6
29.7±4.
5
16 31.2±3. 32.1±2. 35.2±0. 40.6±1. 41.2±2. 35.9±5. 33.8±4.
Chapter 4: Thermal stability of palm olein blended with rice bran oil 55
0 4 4 8 1 0 9
24 36.5±3.
0
37.3±2.
5
40.5±0.
9
46.8±1.
8
47.8±1.
6
40.9±5.
8
39.0±5.
6
32 42.5±3.
1
45.5±2.
6
49.6±1.
1
54.3±1.
8
56.0±1.
2
49.3±5.
9
47.5±4.
6
40 49.4±2.
9
54.8±3.
2
61.3±0.
5
62.8±2.
1
65.5±2.
2
61.3±4.
6
59.0±5.
3 n = 9
Chapter 4: Thermal stability of palm olein blended with rice bran oil 56
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
0 8 16 24 32 40
Heating Time (Hours)
Ove
rall
colo
r di
ffer
ence
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.1 Changes in overall color difference of palm olein blended with rice bran oil
in heating method
Chapter 4: Thermal stability of palm olein blended with rice bran oil 57
0.00
10.00
20.00
30.00
40.00
50.00
60.00
0 8 16 24 32 40
Frying Time (Hours)
Ove
rall
colo
r di
ffer
ence
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.2 Changes in over all color difference of palm olein blended with rice bran oil
in frying method
Chapter 4: Thermal stability of palm olein blended with rice bran oil 58
0.00
20.00
40.00
60.00
80.00
100 .00
120 .00
140 .00
0 8 16 24 32 40
Heating Time (Hours)
Vis
cosi
ty (c
entip
oise
)
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.3 Changes in viscosity of palm olein blended with rice bran oil in heating
method
Chapter 4: Thermal stability of palm olein blended with rice bran oil 59
0.00
20.00
40.00
60.00
80.00
100 .00
120 .00
140 .00
0 8 16 24 32 40
Frying Time (Hours)
Vis
cosi
ty (c
entip
oise
)
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.4 Changes in viscosity of palm olein blended with rice bran oil in frying
method
Chapter 4: Thermal stability of palm olein blended with rice bran oil 60
150 .0
200 .0
250 .0
0 8 16 24 32 40
Heating Time (Hours)
Smok
e po
int (
o C)
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.5 Changes in smoke point of palm olein blended with rice bran oil in heating
method
Chapter 4: Thermal stability of palm olein blended with rice bran oil 61
150 .0
200 .0
250 .0
0 8 16 24 32 40
Frying Time (Hours)
Smok
e po
int (
o C)
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.6 Changes in smoke point of palm olein blended with rice bran oil in frying
method
Chapter 4: Thermal stability of palm olein blended with rice bran oil 62
0.000
0.200
0.400
0.600
0.800
1.000
0 8 16 24 32 40
Heating Time (Hours)
Free
fatt
y ac
id (%
)
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.7 Changes in free fatty acid of palm olein blended with rice bran oil in
heating method
Chapter 4: Thermal stability of palm olein blended with rice bran oil 63
0.000
0.200
0.400
0.600
0.800
1.000
1.200
1.400
1.600
0 8 16 24 32 40
Frying Time (Hours)
Free
fatt
y ac
id (%
)
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.8 Changes in free fatty acid of palm olein blended with rice bran oil in frying
method
Chapter 4: Thermal stability of palm olein blended with rice bran oil 64
0.000
1.000
2.000
3.000
4.000
5.000
6.000
7.000
0 8 16 24 32 40
Heating Time (Hours)
Pero
xide
val
ue (m
eq/k
g)
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.9 Changes in peroxide value of palm olein blended with rice bran oil in
heating method
Chapter 4: Thermal stability of palm olein blended with rice bran oil 65
0.000
2.000
4.000
6.000
8.000
10.000
12.000
0 8 16 24 32 40
Frying Time (Hours)
Pero
xide
val
ue (m
eq/K
g)
(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)
Figure 4.10 Changes in peroxide value of palm olein blended with rice bran oil in
frying method
64
CHAPTER 5
SUMMARY
The improvement in thermal and cold stabilities of palm olein (PO) blended
with rice bran oil (RBO) was investigated in this study. According to the cold stability
test, the oil blended between PO and high RBO could not resist the fat crystal
formation on storage temperature at 15oC. In contrast, all the blended oils remarkably
displayed the excellent resistant to crystallization at 20oC and room temperature. All
blends could retard the crystal formation and remain completely clear and transparent
at 20oC and room temperature for 30 days of experiment. Thus, the effective and
suitable temperature was about 20oC to maintain the blends clear without any
cloudiness. In addition, the blends of PO with 40-60% RBO considerably provided the
most resistance to crystallization of fats. The blended PO with 60% RBO decreased
the cloud point to 5.4oC as compared with 7.3oC of fresh PO. However, all blended oil
did not pass cold test so they were not suitable for salad oil making.
According to the thermal stability test, the blends of PO: RBO in 50:50 ratio
was recommended as the best suitable proportion for frying process since it colud
exhibit superior oxidative stability for 40 hours of heating and frying. This proportion
remarkable decreased FFA content, PV, viscosity, and overall color difference and also
elevated the smoke point.
In future, the blended oil is an alternative source potentially utilize in frying
industry, and capable to modify their properties via the addition of the fat crystal
inhibitors such as sorbitan tristearate and other unsaturated oils such as SBO or SFO to
receive the excellent cold stability, or may add the natural antioxidants in its, for
instance, rosemary extract and sage. The appropriate parameters to measure the oil
deterioration will be further investigation.
65
APPENDIX A
A.O.C.S. Official Method Cc 6-25
Cloud Test
Definition: The cloud point is that temperature at which, under the conditions of this
test, a cloud is induced in the sample caused by the first stage of crystallization.
Scope: Applicable to all normal animal and vegetable fats.
A. Apparatus:
1. Oil sample bottle, 115 ml (4 oz.).
2. Thermometer, A.O.C.S. Specification H 6-40
3. Water bath made up of water, chipped ice and water, or chipped ice, salt and
water, depending upon the temperature required. The temperature of the cloud
bath shall be not less than 2oC. nor more than 5oC. Below the cloud point. A
beaker or sauce pan is a convenient container for this purpose.
B. Procedure:
1. The sample must be completely dry before making the test. Heat 60 to 75 g of
sample to 130oC. Immediately before making the test. Pour ca 45 ml of the
heated fat into an oil sample bottle.
2. Begin to cool the bottle and contents in the water bath, stirring enough to keep
the temperature ca 10oC above the cloud point, begin stirring steadily and
rapidly in a circular motion so as to prevent supercooling and solidification of
fat crystals on the sides or bottom of the bottle.
3. From this point on do not remove the thermometer from the sample, since to do
so may introduce air bubbles which will interfere with the test. The test bottle
is maintained in such a position that the upper levels of the sample in the bottle
and the water in the bath are about the same.
4. Remove the bottle from the bath and inspect regularly. The cloud point is that
temperature at which that portion of the thermometer immersed in the oil is no
longer visible when viewed horizontally through the bottle and sample.
Appendix A 66
A.O.C.S. Official Method Cc 11-53
Cold Test
Definition: This method measures the resistance of the sample to crystallization and
is commonly need used as an index of the winterizing or similar stearin
removing processes.
Scope: Applicable to all normal, refined and dry, animal and vegetable oils.
A. Apparatus
1. Oil sample bottles, 115 ml. (4 oz). These must be completely clean and dry.
2. Chipped ice and water bath at 0oC. Prepare by filling a container (pail or
bucket 4 to 6 lb, capacity) with finely chipped ice. Add cold water sufficient to
fill to the top of the sample bottle when it is immersed.
B. Procedure:
1. Filter a sufficient quantity of sample (200 to 300 ml) through filter paper and
then heat the filtered portion. Stir the sample while heating and remove from
the heat source immediately when the temperature reaches 130oC (see Note 1).
2. Fill an oil sample bottle completely full with the sample and insert a cork
tightly. Adjust to 25oC in water bath and then seal with paraffin.
3. Immerse the bottle containing the sample in the ice and water bath so that the
entire bottle is covered with the water and ice.
4. Replenish the ice as often as is necessary to keep the bath solidly packed,
otherwise the bath temperature will not remain at 0oC, as specified. This
temperature is essential.
5. At the end of 5.5 hours, remove the bottle from the bath and examine closely
for fat crystals or cloudiness. Do not mistake small and finely dispersed air
bubbles for fat crystals. To pass the test the sample must be clear, limpid, and
brilliant (see Note 2).
C. Notes:
1. The purpose of the preliminary heat treatment is to remove traces of moisture
and to destroy any crystal nuclei which may be present. Either will interfere
with the test, causing cloudiness or premature crystallization.
Appendix A 67
2. If it is desired, the test may be continued by re-examination of the sample at
hourly intervals after the first 5.5 hours examination. However, in doing this,
the sample should be returned to the bath as promptly as possible after each
inspection so that the temperature will not increase by any significant amount.
Appendix A 68
Table A-1 Cloud point and cold test of PO blended with RBO
Ratio Cloud points Cold test*
PO:RBO (oC) (0oC; 5.5 hours.)
0:100 2.7 Negative
10:90 3.5 Negative
20:80 4.2 Negative
30:70 4.6 Negative
40:60 5.3 Negative
50:50 5.9 Negative
60:40 6.2 Negative
70:30 6.3 Negative
80:20 6.6 Negative
90:10 6.9 Negative
100:0 7.7 Negative
*Negative : Did not pass through cold test according to AOCS Cc 11-53
Appendix A 69
(a) (b)
(c) (d)
(e) (f)
Figure A-1. Cold stability of palm olein blended with rice bran oil stored at various
temperatures at day 10, 20, 30, 40, 50, and day 60.
Appendix A 70
(a1) (a2)
(b1) (b2)
(c1) (c2)
Figure A-2 Cold stability of blends of palm olein with rice bran oil after 5 days at
(a) 15oC (b) 20oC (c) RT
Appendix A 71
(a1) (a2)
(b1) (b2)
(c1) (c2)
Figure A-3 Cold stability of blends of palm olein with rice bran oil after 10 days at
(a) 15oC (b) 20oC (c) RT
Appendix A 72
(a1) (a2)
(b1) (b2)
(c1) (c2)
Figure A-4 Cold stability of blends of palm olein with rice bran oil after 15 days at
(a) 15oC (b) 20oC (c) RT
Appendix A 73
(a1) (a2)
(b1) (b2)
(c1) (c2)
Figure A-5 Cold stability of blends of palm olein with rice bran oil after 20 days at
(a) 15oC (b) 20oC (c) RT
Appendix A 74
(a1) (a2)
(b1) (b2)
(c1) (c2)
Figure A-6 Cold stability of blends of palm olein with rice bran oil after 25 days at
(a) 15oC (b) 20oC (c) RT
Appendix A 75
(a1) (a2)
(b1) (b2)
(c1) (c2)
Figure A-7 Cold stability of blends of palm olein with rice bran oil after 30 days at
(a) 15oC (b) 20oC (c) RT
76
APPENDIX B
A.O.C.S. Official Method Cc 9a-48
Smoke, Flash, and Fire Points
Definition: These methods determine the temperature at which the sample will
smoke, flash, or burn.
Scope: Applicable to animal, vegetable, and marine fats and oils. Flash point not
applicable to samples which flash point below 300oF. (148.9oC).
A. Apparatus:
1. Cabinet constructed of the materials and in accordance with the dimensions
shown in the illustration.
2. Thermometer, A.O.C.S. specification H 5-40.
3. Cleveland open flash cup, A.S.T.M. Designation D 92-33, constructed of brass
and conforming to the dimensional requirements prescribed in Table 1. The
beveled edge of the cup is at angle of ca 45o. There may be a fillet of ca 5/32
inch (3.97 mm) in radius inside the bottom of the cup.
4. Heating plate, constructed of brass, cast iron, wrought iron, or steel, ¼ inch
(6.35 mm) thick and 6 inches (152.4 mm) in diameter. There is plane
depression 1/32 inch (0.79 mm) deep in the center of the plate with diameter
just sufficient to fit the cup and centered with the circular opening cut through
the plate, 2 3/16 inches (55.0 mm) in diameter. The plate is covered with a
sheet of hard asbestos board 6.35mm thick and of the same shape as the metal
plate.
Appendix B 77
Table 1 Dimensional Requirement for Cleveland Open Flash Cup.
Inches Mill
Min. Normal Max. Min. Normal Max.
Inside dia. immediately
below filling mark 2 15/32 2 1/2 2 17/32 62.7 63.4 64.3
Outside dia. below
flange 2 21/32 2 11/16 2 23/32 67.5 68.3 69.1
Inside height from center
of bottom to rim 1 9/32 15/16 1 11/32 32.5 33.3 34.1
Thickness of bottom 7/64 1/8 9/64 2.8 3.2 3.6
Distance from rim to
filling mark 23/64 3/8 25/64 9.1 9.5 9.9
Distance lower surface
flange to bottom of cup 1 7/32 1 ¼ 19/32 31.0 31.8 32.6
Vertical distance upper
surface flange to rim 7/64 1/8 9/64 2.8 3.2 3.6
Thickness of rim 5/64 3/32 7/64 2.0 2.4 2.8
Width of lower surface
of flange 9/16 19/32 5/8 14.3 15.1 15.9
5. Heat source, gas burner, alcohol lamp, or electric heater with rheostat control.
Whatever form of heat is used under no circumstances are the products of
combustion or free flame allowed to come up around the cup. If a flame heater
is used, it may be protected from drafts or excessive radiation with any suitable
shield that does not project above the upper surface of the asbestos board. The
heat source is centered under the plate opening and must not produce local
superheating.
Appendix B 78
6. Metal flame test burner.
Smoke Point Cabinet
B. Procedure:
(a) Smoke Point.
1. Fill the cup (see Note 1) with the oil or melted fat sample so that the top
of the meniscus is exactly at the filling line and adjust the position of
the apparatus so that the beam of light is directed across the center of
the cup. Suspend or secure the thermometer in a vertical position in the
center of the dish with the bottom of the bulb ca 6.35 mm from the
bottom of the cup.
2. Heat the sample rapidly to within ca 75oF (41.7oC) of the smoke point.
Thereafter, regulate the heat so that the temperature of the sample
increases at the rate of 9oF to 11oF (5oC to 6.1oC) per minute. The
smoke point is the temperature indicated by the thermometer when the
sample gives off a thin, continuous stream of bluish smoke. In some
Appendix B 79
cases, a slight puff appears before the sample begins to smoke
continuously. This is disregarded.
(b) Flash Point.
1. The flash and fire points may be conducted without the cabinet but in
room or compartment free from air drafts and darkened sufficiently so
that the flash is readily discernible. Avoid breathing over the surface of
the sample.
2. Fill the cup with the oil or melted fat sample so that the top of the
meniscus is exactly at the filling line. Suspened or secure the
thermometer in a vertical position with the bottom of the bulb ca 6.35
mm from the bottom of the cup and in a position half way between the
center and back of the cup.
3. Heat the sample at a rate not to exceed 30oF (16.7oC) rise per minute to
within ca 100oF (55.6oC) of the flash point. Thereafter regulate the rate
of heating so that the temperature of the sample increases 9oF to 11oF
(5oC to 6.1oC) per minute.
4. Apply the test flame, which is ca 1/8 inch (3.17mm.) in diameter as the
temperature reaches each successive 5oF (2.8oC) mark. Pass the flame
in a straight line or on the circumference of a circle having a radius of at
least 150 mm. (ca 6 inches) across the center of the cup and the right
angles to the diameter passing through the thermometer. The test flame
shall, while passing across the surface of the sample, be in the plane of
the upper edge of the cup. The time for the passage of the test flame
across the cup shall be ca 1 second.
5. The flash point is the temperature indicated by the thermometer when a
flash appears at any point on the surface of the sample. The true flash
must not be confused with a bluish halo that sometimes surrounds the
test flame.
Appendix B 80
(c) Fire Point.
1. Continue the heating, after the flash point determination, as directed in
paragraph 3 and in the manner prescribed for the flash point until the
fire point is reached.
2. The fire point is the temperature indicated by the thermometer when
application of the test flame causes burning for a period of at least 5
seconds.
C. Note:
1. It is imperative that the apparatus, especially the cup, be scrupulously clean and
free from any substance that may cause smoke to appear ahead of the true
smoke point.
Appendix B 81
A.O.C.S. Official Method Ca 5a-40
Free Fatty Acids
Definition: This method determines the free fatty acids existing in the sample.
Scope: Applicable to crude and refined vegetable and marine oils and animal fats.
A. Apparatus:
1. Oil sample bottles, 115 or 230 ml (4 or 8 oz) or 250 ml Erlenmeyer flasks.
B. Reagents:
1. Ethyl alcohol, 95% (U.S.S.D. Formulas 30 and 3A are permitted). The alcohol
must give a definite, distinct and sharp end-point with phenolphthalein and
must be neutralized with alkali to a faint but permanent pink color just before
using.
2. Phenolphthalein indicator solutions, 1% in 95% alcohol (see Note 1).
3. Sodium hydroxide solutions, accurately standardized.
C. Procedure:
F.F.A. Range, % Grams of Sample Ml. of Alcohol Strength of Alkali
0.00 to 0.2 56.4 50±0.2 0.1 N
0.2 to 1.0 28.2 50±0.2 0.1 N
1.0 to 30.0 7.05 75±0.05 0.25 .N
30.0 to 50.0 7.05 100±0.05 0.25 or 1.0 N
50.0 to 100 3.525 100±0.001 1.0 N
1. Samples must be well mixed and entirely liquid before weighing.
2. Use the table above to determine quantities to be used with various ranges of
fatty acids. Weight the designated size of sample into an oil-sample bottle or
Erlenmeyer flask (see Note 2).
3. Add the specified amount of hot, neutralized alcohol and 2 ml of indicator.
4. Titrate with alkali shaking vigorously to the appearance of the first permanent
pink color of the same intensity as that of the neutralized alcohol before
addition of the sample. The color must persist for 30 seconds.
Appendix B 82
D. Calculations:
1. The percentage of free fatty acids in most types of fats and oils is calculated as
oleic acid, although in coconut and palm kernel oils it is frequently expressed
as lauric acid and in palm oil in terms of palmitic acid.
a. Free fatty acids as oleic, % =
Ml. of alkali × N × 28.2
Weight of sample
b. Free fatty acids as lauric, % =
Ml. of alkali × N × 20.0
Weight of sample
c. Free fatty acids as palmitic, % =
Ml. of alkali × N × 25.6
Weight of sample
2. The free fatty acids are frequently expressed in terms of acid value instead of %
free fatty acids. The acid value is defined as the number of mg of KOH necessary
to neutralize 1g of sample. To convert % free fatty acids (as oleic) to acid value,
multiply the former by 1.99.
E. Notes:
1. Isopropanol, 99%, may be used as an alternate solvent with crude and refined
vegetable oils.
2. Cap bottle and shake vigorously for one minute if oil has been blanketed with
carbon dioxide gas.
Appendix B 83
A O. C. S. Official Method Cd 8-53
Peroxide Value
Definition: This method determines all substances, in terms of milli-equavalents of
peroxide per 1000 grams of sample, which oxidize potassium iodide under the
conditions of the test. These are generally assumed to be peroxides or other
similar products of fat oxidation.
Scope: Applicable to all normal fats and oils including margarine. This method is
highly empirical and any variation in procedure may result in variation in
results.
A. Apparatus:
1. Pipet, Mohr, measuring type, 1 ml capacities.
2. Erlenmeyer flasks, glass-stopped, 250 ml.
B. Reagents:
1. Acetic acid-chloroform solution. Mix 3 parts by volume of glacial acetic acid,
reagent grade, with 2 parts volume of chloroform, U.S.P. grade.
2. Potassium iodide solution, saturated solution of KI, A.C.S. grade, in recently
boiled distilled water. Make sure the solution remains saturated as indicated by
the presence of undissolved crystals. Store in the dark. Test daily by adding 2
drops of starch solution to 0.5 ml of potassium iodide solution in 30 ml of
acetic-chloroform solution. If a blue color is formed which requires more than
1 drop of 0.1 N sodium thiosulfate solutions to discharge, discard the iodide
solution and prepare a fresh solution.
3. Sodium thiosulfate solution, 0.1 N, accurately standardized.
4. Sodium thiosulfate solution, 0.01 N, accurately standardized. This solution
may be prepared by accurately pipeting 100 ml of the 0.1 N solution into a
1000 ml volumetric flask and diluting to volume with recently boiled distilled
water.
5. Starch indicator solution, 1.0% of soluble starch in distilled water.
C. Procedure for Fats and Oils:
1. Weigh 5.00±0.05 g of sample into a 250 ml . glass-stopped Erlenmeyer flask
and then add 30 ml of the acetic-chloroform solution. Swirl the flask until the
Appendix B 84
sample is dissolved in the solution. Add 0.5 ml of saturated potassium iodide
preferably using Mohr type measuring pipet.
2. Allow the solution to stand with occasional shaking for exactly 1 minute and
then add 30 ml of distilled water.
3. Titrate with 0.1 N sodium thiosulfate adding it gradually and with constant and
vigorous shaking. Continue the titration until the yellow color has almost
disappeared. Add ca 0.5 ml starch indicator solution. Continue the titration,
shaking the flask vigorously near the endpoint to liberate all the iodide from the
chloroform layer. Add the thiosulfate dropwise until the blue color has just
disappeared.
Note: If the titration is less than 0.5 l, repeat the determination using 0.01 N
sodium thiosulfate solutions.
4. Conduct a blank determination of the reagents daily. The blank titration must
not exceed 0.1 ml of the 0.1 N sodium thiosulfate solution.
D. Calculation:
1.Peroxide value as milliequavalents of peroxide per 1000 g of sample =
(S-B) (N) (1000)
weight of sample
B = Titration of blank.
S = Titration of sample.
N = Normality of sodium thiosulfate solution.
E. Procedure for Margarine:
1. Proceed as directed above in paragraphs 1 through 4 after preparation of the
sample as directed below.
2. Melt sample by heating with constant stirring on hot plate set at low heat, or by
heating in air oven at 60-70oC. Avoid excessive heating and particularly
prolonged exposure of oil to temperatures above 40oC.
3. When completely melted, remove the sample from the hot plate or oven and
allow to settle in a warm place until the aqueous portion and most of the milk
solids have settled to the bottom.
Appendix B 85
4. Decant the oil into a clean beaker and filter through a Whatman No. 4 (or
equavalent) into another clean beaker. Do not reheat unless absolutely
necessary for filtration. The sample should be clear and brilliant.
Appendix B 86
Brookfield Viscometer
(Synchro-lectric)
Model LVF100
How to operate
1. Attach spindle to lower shaft. It is best to lift the shaft slightly while it is held
firmly with one hand whole screwing the spindle on with the other. Care
should be taken to avoid putting side thrust on the shaft to protect its alignment.
2. Insert spindle in the test material until the fluid’s level is at the immersion
groove cut in the spindle’s shaft. With a disc type spindle it is sometimes
necessary to tilt the instrument slightly while immersing to avoid trapping air
bubbles on its surface. (You may find it more convenient to immerse the
spindle in this fashion before attaching it to the Viscometer). Care should be
taken not to hit the spindle against the sides of the fluid container while it is
attached to the Viscometer, since this too can damage the shaft alignment.
3. Level the Viscometer. The bubble level on all models will be of help in this
respect.
4. Depress the clutch and turn on the Viscometer’s motor: following the
procedure of having the clutch depressed at this point will prevent unnecessary
wear. Release the clutch and allow the dial to rotate until the pointer stabilizes
at a fixed position on the dial. The time required for stabilization will depend
on the speed at which the spindle rotates: at speeds above 4 rpm this will
generally be about 20-30 seconds, while at lower speeds it may take the time
required for one revolution of the dial. It is possible to observe the pointer’s
position and stability at low speeds while the dial rotates but at higher speeds it
will be necessary to depress the cutch and snap the motor switch to stop the
instrument with the pointer in view. Very little practice is needed to stop the
dial at the right point.
5. If check readings are required, start the Viscometer with the clutch still
depressed, holding the original reading, and then release. This will speed up
readings by reducing oscillation of the pointer. If pointer does not stabilize, the
material may be either thixotropic or its temperature may not be constant.
Appendix B 87
Having the spindle at the temperature of the test material will eliminate the
latter possibility.
6. The viscosity of the test material can easily be obtained by consulting the
Factor Finder supplied with the Viscometer for use with all model
7. To convert viscometer dial reading to centipoises (mPa⋅s): adjust slide until
viscometer model and spindle number being used appear in the window.
Multiply reading noted on viscometer 0-100 scale by factor shown beside
speed at which measurement is being made.
Dial reading × Factor = Viscosity in centipoises (mPa⋅s)
8. Full scale viscosity range for any speed and spindle combination is equal to the
factor × 100
Factor × 100 = Full scale range
Appendix B 88
Table B-1 Overall color difference of palm olein blended with rice bran oil in heating
method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 0.0±0.0 4.4±2.2 10.6±8.0 22.1±9.5 35.5±8.3 47.7±6.7
40:60 0.0±0.0 9.8±0.5 22.4±1.2 34.1±0.3 47.5±0.2 59.0±1.3
45:55 0.0±0.0 19.7±1.0 37.1±1.1 51.4±1.0 63.4±1.8 69.9±2.4
50:50 0.0±0.0 15.7±3.3 31.6±2.7 39.4±4.9 58.1±6.1 69.3±7.8
55:45 0.0±0.0 10.2±0.5 22.4±0.8 32.6±1.9 44.5±1.5 54.7±0.5
60:40 0.0±0.0 11.0±0.5 21.4±0.3 30.7±0.3 41.2±1.3 52.0±2.8
100:0 0.0±0.0 14.9±1.6 22.4±1.4 31.6±2.2 42.9±1.6 53.0±1.5 n = 3
Appendix B 89
Table B-2 Overall color difference of palm olein blended with rice bran oil in frying
method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 0.0±0.0 5.1±4.3 11.1±6.6 16.4±7.0 24.5±6.9 33.9±7.3
40:60 0.0±0.0 9.4±0.9 16.0±1.2 21.4±1.7 30.5±0.8 42.4±1.7
45:55 0.0±0.0 9.9±5.6 17.3±6.2 24.9±4.1 32.6±4.2 41.1±5.9
50:50 0.0±0.0 14.2±1.5 22.6±1.8 35.7±12.3 40.3±5.6 50.6±6.5
55:45 0.0±0.0 11.3±2.5 16.3±4.9 21.4±5.8 29.9±6.0 42.1±4.9
60:40 0.0±0.0 10.0±4.9 14.2±5.2 19.5±5.9 28.1±4.9 39.8±5.7
100:0 0.0±0.0 9.8±2.7 10.7±3.3 16.1±3.3 22.1±3.1 29.1±3.4 n = 3
Appendix B 90
Table B-3 Viscosity of palm olein blended with rice bran oil in heating method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 47.5±2.3 53.5±2.3 69.6±2.3 72.0±1.5 86.0±2.3 100.5±6.5
40:60 45.5±7.6 52.5±6.9 59.0±5.7 73.0±13.5 82.0±10.2 92.0±9.8
45:55 45.5±2.3 54.5±0.9 63.0±1.5 78.0±19.9 90.5±6.8 112.5±13.3
50:50 42.0±2.6 47.0±1.7 54.0±2.6 59.5±5.4 72.0±5.2 84.0±10.4
55:45 46.5±3.9 53.5±4.6 59.0±3.1 76.0±11.4 82.5±9.4 94.5±11.7
60:40 45.0±3.9 54.0±10.8 61.5±9.1 71.0±11.1 82.0±10.6 104.5±23.5
100:0 49.5±2.6 53.5±8.8 59.5±4.3 66.5±6.1 76.0±8.3 88.5±9.4 n = 3
Appendix B 91
Table B-4 Viscosity of palm olein blended with rice bran oil in frying method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 46.0±1.7 53.0±1.7 60.0±1.5 70.5±1.5 83.0±6.2 101.0±13.9
40:60 46.5±6.9 53.2±11.9 64.5±10.5 73.5±11.3 81.5±11.3 100.5±14.8
45:55 45.3±1.6 48.8±1.2 54.3±3.7 63.3±5.5 73.5±6.1 85.0±7.9
50:50 40.8±2.8 47.8±1.6 60.0±0.0 70.8±1.9 78.0±2.3 92.0±10.5
55:45 48.5±9.8 53.0±7.6 69.0±3.2 70.5±15.8 82.0±18.1 101.0±32.1
60:40 46.5±9.1 54.0±13.1 63.5±12.0 73.0±14.6 92.5±13.4 113.5±16.9
100:0 44.0±4.8 60.0±4.8 57.5±5.7 64.5±6.5 73.0±7.4 82.0±8.7 n = 3
Appendix B 92
Table B-5 Smoke point of palm olein blended with rice bran oil in heating method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 212.0±2.0 208.7±1.2 199.3±4.2 196.3±3.2 190.7±3.1 186.0±2.6
40:60 212.7±4.2 207.0±1.0 198.7±2.9 194.0±2.0 186.0±2.6 184.0±3.6
45:55 205.3±3.5 196.7±1.5 191.0±1.0 181.3±8.1 180.7±1.2 175.7±2.1
50:50 205.7±3.1 199.0±4.4 193.3±4.2 184.7±2.5 180.0±4.0 179.7±6.7
55:45 210.0±4.6 204.0±1.0 196.3±5.0 192.7±2.3 188.7±2.1 183.7±1.5
60:40 209.7±4.5 205.7±3.2 194.7±4.2 190.0±6.1 188.0±2.0 186.0±4.0
100:0 201.0±1.0 196.0±1.0 190.7±2.5 184.0±1.0 179.7±1.5 176.7±2.3 n = 3
Appendix B 93
Table B-6 Smoke point of palm olein blended with rice bran oil in frying method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 213.0±1.0 203.3±3.2 199.7±2.5 191.0±5.6 186.7±4.7 182.0±5.3
40:60 208.0±3.6 203.3±0.6 191.0±1.0 182.0±2.0 177.3±2.5 172.0±3.6
45:55 209.2±3.3 203.0±6.6 191.7±6.0 185.2±5.8 174.7±2.3 170.0±2.0
50:50 207.7±8.0 199.5±5.6 188.0±2.6 181.2±6.5 173.0±1.7 168.3±1.5
55:45 208.0±1.0 200.3±4.0 191.7±0.6 182.0±2.6 174.3±2.1 172.3±3.8
60:40 206.0±1.0 200.7±3.2 191.3±4.6 178.0±2.0 173.0±1.7 168.0±1.7
100:0 202.0±1.7 195.0±3.0 187.7±2.3 181.0±1.0 176.3±1.2 169.7±3.5 n = 3
Appendix B 94
Table B-7 Free fatty acid content of palm olein blended with rice bran oil in heating
method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 0.09±0.01 0.16±0.05 0.21±0.02 0.32±0.09 0.42±0.09 0.55±0.15
40:60 0.11±0.03 0.16±0.05 0.33±0.05 0.49±0.08 0.58±0.03 0.80±0.06
45:55 0.06±0.01 0.14±0.01 0.24±0.04 0.37±0.10 0.45±0.07 0.57±0.03
50:50 0.06±0.01 0.13±0.02 0.22±0.04 0.25±0.02 0.33±0.13 0.47±0.03
55:45 0.12±0.02 0.22±0.06 0.33±0.03 0.53±0.10 0.67±0.03 0.76±0.22
60:40 0.11±0.01 0.22±0.03 0.31±0.03 0.55±0.01 0.71±0.08 0.81±0.09
100:0 0.08±0.00 0.20±0.05 0.31±0.11 0.43±0.14 0.53±0.06 0.74±0.22 n = 3
Appendix B 95
Table B-8 Free fatty acid content of palm olein blended with rice bran oil in frying
method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 0.10±0.01 0.18±0.07 0.27±0.02 0.44±0.12 0.62±0.16 0.72±0.22
40:60 0.12±0.03 0.27±0.02 0.48±0.09 0.78±0.13 0.96±0.12 1.36±0.24
45:55 0.07±0.02 0.17±0.09 0.28±0.16 0.49±0.24 0.69±0.40 0.83±0.49
50:50 0.08±0.03 0.17±0.06 0.34±0.10 0.38±0.11 0.53±0.04 0.60±0.12
55:45 0.12±0.04 0.26±0.03 0.47±0.05 0.75±0.08 1.05±0.08 1.25±0.07
60:40 0.11±0.02 0.25±0.03 0.49±0.04 0.70±0.05 1.02±0.03 1.15±0.17
100:0 0.07±0.00 0.16±0.03 0.30±0.02 0.54±0.03 0.67±0.04 0.88±0.10 n = 3
Appendix B 96
Table B-9 Peroxide value of palm olein blended with rice bran oil on heating method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 1.58±0.62 3.16±1.39 3.62±1.39 2.65±0.60 3.21±1.11 3.00±0.66
40:60 1.31±0.54 2.46±0.31 2.30±0.26 2.39±0.32 2.34±0.38 2.55±0.40
45:55 1.82±0.78 3.80±0.47 4.13±0.17 5.15±0.12 3.41±1.78 4.48±0.66
50:50 1.35±0.38 3.06±0.33 3.00±0.82 3.95±0.92 4.11±0.81 2.71±0.60
55:45 1.20±0.08 2.39±0.46 2.44±0.34 3.07±0.81 2.61±0.42 2.38±0.43
60:40 1.10±0.15 2.73±0.13 2.44±0.39 2.35±0.23 2.13±0.09 2.50±0.42
100:0 1.56±0.62 3.87±1.87 3.39±0.99 3.28±0.23 3.52±1.31 2.83±0.19 n = 3
Appendix B 97
Table B-10 Peroxide value of palm olein blended with rice bran oil in frying method.
Ratio Time (hours)
PO:RBO 0 8 16 24 32 40
0:100 1.87±0.35 5.62±2.52 5.69±1.08 6.69±0.91 6.20±1.48 5.23±1.71
40:60 1.45±0.49 3.59±0.36 3.96±0.40 4.31±0.60 3.79±0.54 3.69±0.70
45:55 1.61±0.22 4.36±2.33 4.93±1.17 5.56±1.67 6.37±1.75 4.89±1.98
50:50 1.49±0.81 6.26±2.64 4.23±1.24 4.03±1.76 4.50±1.69 2.96±1.10
55:45 1.52±0.39 4.34±0.22 4.85±0.67 4.78±0.27 4.97±0.76 4.06±0.23
60:40 1.23±0.28 4.91±0.17 4.02±0.74 4.16±0.56 4.35±0.40 4.49±0.61
100:0 1.68±0.65 6.79±2.77 6.98±1.32 7.71±2.78 7.33±1.66 6.84±1.78 n = 3
Appendix B 98
70.000
80.000
90.000
100 .000
0 8 16 24 32 40
Heating Time (hours)
L*
valu
e
100 PO 100 RBO 40 PO:60 RBO 45 PO:55 RBO50 PO:50 RBO 55 PO:45 RBO 60 PO:40 RBO
Figure B-1 Changes in L* value of palm olein blended with rice bran oil in heating
method
Appendix B 99
80.000
85.000
90.000
95.000
100 .000
0 8 16 24 32 40
Frying Time (hours)
L*
valu
e
100 PO 100 RBO 40 PO:60 RBO 45 PO:55 RBO50 PO:50 RBO 55 PO:45 RBO 60 PO:40 RBO
Figure B-2 Changes in L* value of palm olein blended with rice bran oil in frying
method
Appendix B 100
-10.000
-9.000
-8.000
-7.000
-6.000
-5.000
-4.000
-3.000
-2.000
-1.000
0.0000 8 16 24 32 40
Heating Time (hours)
a* v
alue
100 PO 100 RBO 40 PO:60 RBO 45 PO:55 RBO50 PO:50 RBO 55 PO:45 RBO 60 PO:40 RBO
Figure B-3 Changes in a* value of palm olein blended with rice bran oil in heating
method
Appendix B 101
-10.000
-9.500
-9.000
-8.500
-8.000
-7.500
-7.000
-6.500
-6.000
-5.500
-5.0000 8 16 24 32 40
Frying Time (hours)
a* v
alue
100 PO 100 RBO 40 PO:60 RBO 45 PO:55 RBO50 PO:50 RBO 55 PO:45 RBO 60 PO:40 RBO
Figure B-4 Changes in a* value of palm olein blended with rice bran oil in frying
method
Appendix B 102
10.000
20.000
30.000
40.000
50.000
60.000
70.000
80.000
90.000
100 .000
0 8 16 24 32 40
Heating Time (hours)
b* v
alue
100 PO 100 RBO 40 PO:60 RBO 45 PO:55 RBO50 PO:50 RBO 55 PO:45 RBO 60 PO:40 RBO
Figure B-5 Changes in b* value of palm olein blended with rice bran oil in heating
method
Appendix B 103
10 .000
20 .000
30 .000
40 .000
50 .000
60 .000
70 .000
0 8 16 24 32 40
Frying Time (hours)
b* v
alue
100 PO 100 RBO 40 PO:60 RBO 45 PO:55 RBO50 PO:50 RBO 55 PO:45 RBO 60 PO:40 RBO
Figure B-6 Changes in b* value of palm olein blended with rice bran oil in frying
Method