Angela Chen

Sweeteners from Starch….

Sweeteners from Starch….

Sweeteners from Starch….

Sweeteners from Starch….

Sweeteners from Starch….

Sweeteners from Starch….

Hydrocolloids

Binding water with carbohydrates

Starches- Our #1 Hydrocolloid? Hydrocolloids are substances that will form a gel or

add viscosity on addition of water.

Most are polysaccharides and all form significant H-bonding with water with processing.

Size, structure, and charge are the most important factors relating to texture and physical features of foods

Small versus LargeSmall molecule sugars would create a high

osmotic pressure if stored in sufficient quantities to be useful.

Polymerized sugars reduce the number of molecules present and hence the osmotic effects.

Free polymers are too thick to allow cell to function

Thus, plants store energy into starch granules

AMYLOSELinear polymer of glucoseα 1 - 4 linkagesDigestable by humans (4 kcal/g)250-350 glucose units on average

Varies widely

Corn, wheat, and potato starch ~10-30% amylose

AMYLOPECTINBranched chain polymer of glucoseα 1 - 4 and α 1 - 6 glycosidic linkagesMostly digestible by humans1,000 glucose units is common

Branch points every ~15-25 units

StarchAmylose may have a few branched chains

Helical structure with a hydrophobic core Core may contain lipids, metals, etc.

Amylose to Amylopectin ratios ~ 1:4 Varies with the plant source

Waxy starches are ~100% amylopectinSugary “mutant” starches have more amylose

Straight-Chained Starch = AmyloseGlucose polymer linked α-1,4 and α-1,6

Starch

Birefringence When starch granules are viewed under the microscope by polarized light they exhibit a phenomenon known as birefringency - the refraction of polarized light by the intact crystalline regions to give a characteristic "Maltese cross" pattern on each granule. The cross disappears upon heating and gelatinization.

Modified Starches

Gelatinization is the easiest modification Heated in water then dried.

Acid and/heat will form “dextrins” α-Amylase

hydrolyzes α (1-4) linkage random attack to make shorter chains

β-Amylase Also attacks α (1 - 4) linkages Starts at the non-reducing end of the starch chain Gives short dextrins and maltose

Both enzymes have trouble with α (1 - 6) linkages

Gelatinization of Starch Native starch granules are insoluble in cold water, despite

some “swelling” Heated water increases kinetic energy, breaking some

intermolecular bonds, and allows water to penetrate The gelatinization point is where crystallinity is lost

GTR is the temperature range over which gelatinization occurs.

As water is bound, the viscosity increases. GTR is different from different starch types There must be enough water to break open and bind to

the starch hydrogen binding sites.

Starch grains swell when heated in water

Gelatinization

H-bonds break, amylose can spill from the grain

Gelatinization is done

Gains may loose integrity

During cooling, junction zones form Between amylose and amylopectin

water

water

water

waterwater

water

Water is trappedForming a gel.

WATER

As the gel dehydrates and/or junction zonesTighten, water is “squeezed” from the gel, in a syneresis process.

Starch ModificationsCross-linking (common modification)

Alkali treatment (pH 7.5-12) with salt Phosphorus oxychloride Sodium trimetaphosphate Adipic and acetic anhydride Starch phosphates formed after neutralization

Cross-LinkingResists viscosity breakdownResists prolonged heating effectsResists high shear ratesResists high acid environments Increased viscosity Increased texture

Starch ModificationsStarch Substitutions

Adding monofunctional groups “Blocking Groups” added to the starch Acetyl (2.5% max starch acetates) Hydroxypropyl, phosphates, ethers

Slows retrogradation (re-association of amylose) Lowers GTR, stabilizes the starch

Acetate + Starch

Starch ModificationsOxidation and Bleaching

Hydrogen peroxide Ammonium persulfate Na/Ca hypochlorite

0.0082 lbs chlorine/pound of starch

K-permanganate Na-chlorite

Whitens the starch Removes carotenes and other natural pigments

~25% of oxidizers break C-C linages ~75% of oxidizers will oxidize the hydroxyl groups Lowers viscosity, improves clarity of gels

Polysaccharide Breakdown Products

Hydrolytic Products Maltose Maltitol Maltodextrins Dextrins Dextrans

Maltose = glucose disaccharide Maltitol = example of a “polyol” Maltodextrins = enzyme converted starch fragments

DextrDextriinsns = starch fragments (α-1-4) linkages produced by hydrolysis of amylose

DextrDextraansns = polysaccharides made by bacteria and yeast metabolism, fragments with mostly α (1 - 6) linkages

Maltodextrins and enzyme-converted starch:

STARCHSTARCH fermentation SUGARS

ETHANOL

MODIFIED STARCHESMODIFIED STARCHES

GELATINIZED STARCHGELATINIZED STARCH alpha amylase Maltodextrins

Corn Syrups

Sugars

The smaller the size of the products in these reactions, the higher the dextrose equivalence (DE), and the sweeter they are

Starch DE = 0 Glucose (dextrose) DE = 100

Maltodextrin (MD) DE is <20

Corn syrup solids (CS) DE is >20

Low DE syrup alpha amylase MD beta amylase High DESyrup

DextrinizationA non-enzymatic method to product low-

molecular weight fragments High heat treatment of acidified starch “Pyro-conversion” of starch to dextrins

Both breaks and re-forms bonds Wide-range of products formed

Vary in viscosity Solubility Color (white, yellow) Reducing capacity Stability

Hydrocolloids

Binding water with carbohydrates

“Gums”

“Vegetable gum” polysaccharides are substances derived

from plants, including seaweed and various shrubs or trees, have the ability to hold water, and often act as thickeners, stabilizers, or gelling agents in various food products.

Plant gums - exudates, seeds (guar, xanthan, locust bean, etc)

Marine hydrocolloids - extracts from seaweeds(Carageenan, agar, alginates)

Microbiological polysaccharides - exocellular polysaccharides

Modified, natural polysaccharides

FUNCTIONS IN FOOD Gelation Viscosity Suspension Emulsification and stability Whipping Freeze thaw protection Fiber (dietary fiber)

Gut health Binds cholesterol

STRUCTURAL CONSIDERATIONS

Electrical charge, pH sensitive Interactions with

Oppositely charged molecules Salts Acids

Chain length Longer chains are more viscous

Linear vs Branched chains Inter-entangled, enter-woven molecules

“Structural” Polysaccharides

CellulosePolymer of glucose linked ß-1,4

HemicelluloseSimilar to celluloseConsist of glucose and other monosaccharides

Arabinose, xylose, other 5-carbon sugars

PectinPolymer of galacturonic acid

MODIFIED CELLULOSESChemically modified celluloseDo not occur naturally in plantsSimilar to starch, but β-(1,4) glycosidic bondsCarboxymethyl cellulose (CMC) most common

Acid treatment to add a methyl group Increases water solubility, thickening agent Sensitive to salts and low pH

Fruit fillings, custards, processed cheeses, high fiber filler

PECTINS Linear polymers of galacturonic acid

Gels form with degree of methylation of its carboxylic acid groups

Many natural sources

Susceptible to degrading enzymes Polygalacturonase (depolymerize) Pectin esterases (remove methyl groups)

Longer polymers, higher viscosity Lower methylation, lower viscosity Increase electrolytes (ie. metal cations), higher viscosity pH and soluble solids impact viscosity

PECTIC SUBSTANCES: cell cementing compound; fruits and vegetables; pectin will form gel with appropriate concentration, amount of sugar and pH.

Basic unit comprised of galacturonic acidgalacturonic acid.

BETA-GLUCANSExtracts from the bran of barley and oatsLong glucose chains with mixed ß-linkagesVery large (~250,000 glucose units)

Water soluble, but have a low viscosity Can be used as a fat replacer Responsible for the health claims (cholesterol) for

whole oat products Formulated to reduce the glycemic index of a food

Beta-Glucan

Beta-glucans occur in the bran of grains such as barley and oats, and they are recognized as being beneficial for reducing heart disease by lowering cholesterol and reducing the glycemic responseglycemic response.

They are used commercially to modify food texture. and as fat replacerfat replacer .

                                                                                                                                                      

         

Beta-Glucan

OthersCHITIN Polymer of N-Acetyl-D-glucosamine Found in the exoskeleton of insects and shellfish Many uses in industry, food and non-food.

INULIN Chains of fructose that end in a glucose molecule

Generally a sweet taste Isolated from Jerusalem artichokes and chicory Act as a dietary fiber Potentially a pre-biotic compound

Paper ReviewProducing fructo-oligosaccharides: For Tuesday

StarchStarch must be cooked to act as a thickening

agent Pre-gelatinized starch is made by quickly

cooking a starch and drying the product. Pre-gelatinized starch rapidly re-hydrates

without further cooking Useful thickening agent Can be used in dried sauces and salad dressings Used in products that do not require more cooking

StarchStarch suspensions are not stable to heating Swollen starch granules break down in hot,

stirred or acidic conditions Combinations (ie. heat and acid) will

depolymerizeCross-linking can help stabilize and slow or

maybe prevent breakdown

Starch Starch gels change their properties during storage Slow retrogradation of amylopectin is common The texture of a starch gel will change and show some

syneresis. Again, modified starch will resist changes during

storage Starch acetates or phosphates are common

modifications, altering the helical arrangements, and slow or inhibit retrogradation.

All stabilized starches must also be labeled as “modified starch” on an ingredient list.

“Vegetable gum” polysaccharides are substances derived

from plants, including seaweed and various shrubs or trees, have the ability to hold water, and often act as thickeners, stabilizers, or gelling agents in various food products.

Plant gums - exudates, seeds (guar, xanthan, locust bean, etc)

Marine hydrocolloids - extracts from seaweeds(Carageenan, agar, alginates)

Microbiological polysaccharides - exocellular polysaccharides

Modified, natural polysaccharides

FUNCTIONS IN FOOD Gelation Viscosity Suspension Emulsification and stability Whipping Freeze thaw protection Fiber (dietary fiber)

Gut health Binds cholesterol

STRUCTURAL CONSIDERATIONS

Electrical charge, pH sensitive Interactions with

Oppositely charged molecules Salts Acids

Chain length Longer chains are more viscous

Linear vs Branched chains Inter-entangled, enter-woven molecules

“Structural” Polysaccharides

CellulosePolymer of glucose linked ß-1,4

HemicelluloseSimilar to celluloseConsist of glucose and other monosaccharides

Arabinose, xylose, other 5-carbon sugars

PectinPolymer of galacturonic acid

MODIFIED CELLULOSESChemically modified celluloseDo not occur naturally in plantsSimilar to starch, but β-(1,4) glycosidic bondsCarboxymethyl cellulose (CMC) most common

Acid treatment to add a methyl group Increases water solubility, thickening agent Sensitive to salts and low pH

Fruit fillings, custards, processed cheeses, high fiber filler

PECTINS Linear polymers of galacturonic acid

Gels form with degree of methylation of its carboxylic acid groups

Many natural sources

Susceptible to degrading enzymes Polygalacturonase (depolymerize) Pectin esterases (remove methyl groups)

Longer polymers, higher viscosity Lower methylation, lower viscosity Increase electrolytes (ie. metal cations), higher viscosity pH and soluble solids impact viscosity

PECTIC SUBSTANCES: cell cementing compound; fruits and vegetables; pectin will form gel with appropriate concentration, amount of sugar and pH.

Basic unit comprised of galacturonic acidgalacturonic acid.

BETA-GLUCANSExtracts from the bran of barley and oatsLong glucose chains with mixed ß-linkagesVery large (~250,000 glucose units)

Water soluble, but have a low viscosity Can be used as a fat replacer Responsible for the health claims (cholesterol) for

whole oat products Formulated to reduce the glycemic index of a food

Beta-Glucan

Beta-glucans occur in the bran of grains such as barley and oats, and they are recognized as being beneficial for reducing heart disease by lowering cholesterol and reducing the glycemic responseglycemic response.

They are used commercially to modify food texture. and as fat replacerfat replacer .

                                                                                                                                                      

         

Beta-Glucan

Yeast ß-Glucan Isolation

Sugar Reactions

(Gluconic acid)(Glucuronic acid)

Properties of GlucoseC1 of glucose is the carbonyl carbonGlucose has 4 chiral centers

Non-super-imposable on its mirror imageCarbons 2, 3, 4, 5 are chiral carbons

The carbonyl carbon (C1) is also the site of many reactions involving glucose They have two enantiomeric forms, D and

L, depending on the location of the hydroxyl group at the chiral carbons.

SugarsThey have two enantiomeric forms, D and L,

depending on the location of the hydroxyl group at the chiral carbons. An enantiomer is one of two stereoisomers that are

mirror images of each other, non-superposable.

Isomerism in which two isomers are mirror images of each other. (D vs L).

Vary in their 3-D space

AnomersAn anomer is one of a special pair of

diastereomeric (isomer) aldoses or ketoses A stereoisomer that is not an enantiomer

They differ only in configuration about the carbonyl carbon (C1 for aldoses and C2 for ketoses)

Carbonyl CarbonsCarbonyl carbons are subject to nucleophilic

attack, since it is electron deficient. Electrons are drawn to this site

-OH groups on the sugar act as the nucleophile, and add to the carbonyl carbon to recreate the ring form

Carbonyl Carbons

Anomers α-anomer (~36%) β- anomer (~64%)

Sugar Anomers => Mutarotation Interconversion of α- and β- anomers The α- and β- anomers of carbohydrates are typically

stable. In solution, a single molecule can interchange between

straight and ring form different ring sizes α and β anomeric isomers

The process is dynamic equilibrium due to reversibility of reaction

All isomers can potentially exist in solution energy/stability of different forms vary

Mutarotation α- and β- anomers

IsomerizationKeto-Enol Tautomerism (equilibration)

Hydrogen migration; switch from SB to DB

Enol is predominant in aldose sugarKeto is predominant in ketose sugarKeto and Enol forms are tautomers of each other

IsomerizationGlucose and mannose are enantiomers, but

with dramatically different propertiesGlucose and fructose are isomers

Pectins in Foods

Plant Cell Wall

Middlelamella

Primary wall

Plasmalemma

Cytoplasm

Vacuole

Nucleolus

Nucleus

Water-Filled

PECTINS Linear polymers of galacturonic acid

Gels form with degree of methylation of its carboxylic acid groups

Many natural sources

Susceptible to degrading enzymes Polygalacturonase (depolymerize); PG Pectin esterases (remove methyl groups), PME

Longer polymers, higher viscosity Lower methylation, lower viscosity Increase electrolytes (ie. metal cations), higher viscosity pH and soluble solids impact viscosity

Composition: polymer of galacturonic acids; may be partially esterifiedesterified.

Pectic Acid

                                                                                                  

                                                                                                                 

Pectin Molecule

Pectins Pectins are important because they form gelsgels

Mechanism of gel formation differs by the degree of esterification (DE) of the pectin molecules DE refers to that percentage of pectin units with a methyl group attached

Free COOH groups can crosslink with divalent cationsdivalent cations

Sugar and acid under certain conditions can contribute to gel structure and formation

LM pectin “low methoxyl pectin”LM pectin “low methoxyl pectin” has DE < 50% ; gelatin is controlled by adding cations (like Ca++ and controlling the pH)

HM pectinHM pectin “high methoxyl pectin” has DE >50% and forms a gel under acidic conditions by hydrophobic interactions and H-bonding with dissolved solids (i.e. sugar)

Hydrophobic attractions between neighboring pectin polymer chainspromote gelation

Ca++ Ca++

ProteinsMany important functions

Functional Nutritional Biological

EnzymesStructurally complex and large compoundsMajor source of nitrogen in the diet

By weight, proteins are about 16% nitrogen

Properties of Amino AcidsAliphatic chains: Gly, Ala, Val, Leucine, IleHydroxy or sulfur side chains: Ser, Thr, Cys, MetAromatic: Phe, Trp, TryBasic: His, Lys, ArgAcidic and their amides: Asp, Asn, Glu, Gln

Properties of Amino Acids:

Aliphatic Side Chains

Aromatic Side Chains

Acidic Side Chains

SulfurSideChains

Properties of Amino Acids:Zwitterions are electrically neutral, but carry a

“formal” positive or negative charge.

The Zwitterion Nature Zwitterions make amino acids good acid-base buffers.

Accepting H+ is acidic environments; donating H+ in basic environments

For proteins and amino acids, the pH at which they have no net charge in solution is called the Isoelectric Point of pI (i.e. IEP).

The solubility of a protein depends on the pH of the solution.

Similar to amino acids, proteins can be either positively or negatively charged due to the terminal amine -NH2 and carboxyl (-COOH) groups.

Proteins are positively charged at low pH and negatively charged at high pH. When the net charge is zero, we are at the IEP.

A charged protein helps interactions with water and increases its solubility.

As a result, protein is the least soluble when the pH of the solution is at its isoelectric point.

Physical Nature of Proteins

Secondary protein structureThe spatial structure the protein assumes along

its axis (its “native conformation” or min. free energy)

This gives a protein functional properties such as flexibility and strength

Tertiary Structure of Proteins3-D organization of a polypeptide chainCompacts proteins Interior is mostly devoid of water or charge groups

3-D folding of chain

Quaternary Structure of ProteinsNon-covalent associations of protein units

ProteinsChanges in structure Denaturation

Breaking of any structure except primary Examples:

Heat Salt/Ions Alcohol pH extremes Shear Enzymes

Emulsoids and Suspensiods

Proteins should be thought of as solids Not in true solution, but bond to a lot of water

Can be described in 2 ways:

Emulsoids- have close to the same surface charge, with many shells of bound water

Suspensoids- colloidal particles that are suspended by charge alone

Functional Properties of Proteins3 major categories Hydration properties

Protein to water interactions Dispersibility, solubility, adhesion, Water holding capacity, viscosity

Structure formation Protein to protein interactions Gel formation, precipitation, Aggregation

Surface properties Protein to interface interactions Foaming, emulsification

1. Hydration Properties (hydration)

Proteins are important hydrocolloids As ingredients, many are sold as dry powders Hydrating and processing w/o denaturation

Solubility- Mostly, denatured proteins are less soluble than native proteins

Many (but not all) proteins (particularly suspensoids) aggregate or precipitate at their isoelectric point (IEP)

Protein viscosity is influenced by amount, size, shape, pH, water content, and solubility of the proteins

2. Structure Formation (protein interactions)

Gels – a 3-D network of protein and water. Attractive and repulsive forces between adjacent polypeptides

Gelation- when denatured proteins aggregate and form an ordered protein matrix Water absorption and thickening Formation of viscous, solid, or visco-elastic gels

For many proteins, heated followed by cooling forms the gel

Texturization – Proteins are responsible for the structure and texture of many foods Meat, bread dough, gelatin Texturized proteins are modified with with salts, acid/alkali,

oxidants/reductants “Pink Slime” Can also be processed to mimic other proteins (i.e. surimi)

3. Surface Properties (interfaces)

Emulsions- Exposure of protein hydrophobic regions to lipids (ie. tertiary structures) Not all proteins make good emulsifiers Can strengthen a normal emulsion system

Foams- trapping gas bubbles in a viscous medium Protein is usually soluble Air bubble size is critical (nebulized air) Duration and shear rate Temperature and physical kinetics Food ingredient interactions (i.e. salt, acid, and lipids)..bad. Metal ions, hydrocolloids, and sugar can increase stability

Enzymes

Enzyme Influencing Factors

Temperature-dependence of enzymesEvery enzyme has an optimal temperature for

maximal activityThe effectiveness of an enzyme: Enzyme activityFor most enzymes, it is 30-40°CMany enzymes denature >45°CEach enzyme is different, and vary by isozymes Often an enzyme is at is maximal activity just

before it denatures at its maximum temperature

pHLike temp, enzymes have an optimal pH where

they are maximally activeGenerally between 4 and 8

with many exceptions

Most have a very narrow pH range where they show activity.

This influences their selectivity and activity.

Water ActivityEnzymes need “free” water to operateLow Aw foods have slower enzyme reactions

Ionic StrengthSome ions may be needed by active sites on the

protein (salting in) Ions may be a link between the enzyme and substrate Ions change the surface charge on the enzyme Ions may block, inhibit, or remove an inhibitor Others, enzyme-specific

Common Enzymes in FoodsPolyphenol oxidasePlant cell wall degrading enzymesProteasesLipasesPeroxidase/CatalaseAmylaseAscorbic acid oxidaseLipoxygenase

Enzyme Influencing Factors Enzymes are proteins that act as biological catalysts They are influenced in foods by:

Temperature pH Water activity Ionic strength (ie. Salt concentrations) Presence of other agents in solution

Metal chelators Reducing agents Other inhibitors

Also factors forInhibition, including:

Oxygen exclusionand

Sulfites

The “Raw Foods” Movement Enzymes present in raw foods help in digesting the foods we eat

But they have to enter the digestive system.

Cooking destroys food enzymes forcing the body to produce more of its own digestive enzymes Eating these enzymes saves your both the work.

Our body has a finite amount of enzyme producing potential The more enyzmes we eat, the more we preserve health and longevity Our digesting enzyme potential can be exhausted.

Enzymes in raw food also carry our "life force" When our ability to produce digestive enzymes is exausted, we die.

Enzymes Before a chemical reaction can occur, the activation energy (Ea)

barrier must be overcome Enzymes are biological catalysts, so they increase the rate of a

reaction by lowering Ea

Enzymes

The effect of temperature is two-fold From about 20, to 35-40°C (for enzymes) From about 5-35°C for other reactions

Q10-Principal: For every 10°C increase in temperature, the reaction rate will double

Not an absolute “law” in science, but a general “rule of thumb”

At higher temperatures, some enzymes are much more stable than other enzymes

Enzymes Enzymes are sensitive to pH – most enzymes active only within a pH range of

3-4 units (catalase has max. activity between pH 3 & 10)

The optimum pH depends on the nature of the enzyme and reflects the environmental conditions in which enzyme is normally active: Pepsin pH 2; Trypsin pH 8; Peroxidase pH 6

pH dependence is usually due to the presence of one or more charged AA at the active site.

Worthington Enzyme Manual

http://www.worthington-biochem.com/index/manual.html

Nomenclature

Each enzyme can be described in 3 ways: Trivial name: -amylase Systematic name: -1,4-glucan-glucono-hydrolase

substrate reaction

Number of the Enzyme Commission: E.C. 3.2.1.1 3- hydrolases (class) 2- glucosidase (sub-class) 1- hydrolyzing O-glycosidic bond (sub-sub-class) 1- specific enzyme

Enzyme Class Characterizations

1. OxidoreductaseOxidation/reduction reactions

2. TransferaseTransfer of one molecule to another (i.e. functional groups)

3. HydrolaseCatalyze bond breaking using water (ie. protease, lipase)

4. LyaseCatalyze the formation of double bonds, often in dehydration reations

5. IsomeraseCatalyze intramolecular rearrangement of molecules

6. LigaseCatalyze covalent attachment of two substrate molecules

Enzyme CommissionEnzyme Nomenclature

International Union of Biochemistry and Molecular Biology (IUBMB)

International Union of Pure and Applied Chemistry (IUPAC)

Joint Commission on Biochemical Nomenclature (JCBN)

IUPAC-IUBMB-JCBNhttp://www.chem.qmul.ac.uk/iubmb/enzyme/

1. OXIDOREDUCTASES

OxidationIsLosing electrons

ReductionIsGaining electrons

Xm+ Xm2+

e-

oxidizedreduced e-

Electron acceptor

Electron donor

Redox active (Transition) metals (copper/ iron containing proteins)

1. Oxidoreductases: GLUCOSE OXIDASE -D-glucose: oxygen oxidoreductase Catalyzes oxidation of glucose to glucono- -lactone

-D-glucose Glucose oxidase D glucono--lactone

FAD FADH2 +H2O

H2O2 O2 D Gluconic acidCatalase

H2O + ½ O2

Oxidation of glucose to gluconic acid

How Glucose Oxidase + Catalase Works:

Reaction 1: Glucose + O2 Gluconic acid + H2O2

Reaction 2: H2O2 H2O + 1/2 O2

Reaction 3: Glucose + 1/2 O2 Gluconic acid

GO

CAT

GO/CAT

1. Oxidoreductases: PEROXIDASE (POD)

Donor: Hydrogen peroxide oxidoreductase

Iron-containing enzyme. Has a heme prosthetic group

Thermo-resistant – denaturation at ~ 85oC

Since is thermoresistant - indicator of proper blanching (no POD activity in properly blanched vegetables)

N N

NN

Fe

1. Oxidoreductases: Catalase

Hydrogen peroxide oxidoreductase Catalyzes conversion of 2 molecules of H2O2 into

water and O2:

Uses H2O2 When coupled with glucose oxidase the net result is

uptake of ½ O2 per molecule of glucose Occurs in MO, plants, animals

H2O2 ------------------- H2O +1/2 O2

1. Oxidoreductases: LIPOXYGENASE

OOH

HH

HC

C

H

H

CC

C

cistrans

HH

H

CC

H

H

CC

C

cis cis

+ O2

……..………

……..

Oxidation of lipids with cis, cis groups into conjugated cis, trans hydroperoxides.

Enzymatic Determination of Starch

or other simple sugars

PRINCIPLE Starch is hydrolyzed

into glucose units by enzymatic conversion

D-glucose can then be quantified by enzymatic methods

1. Oxidoreductases: POLYPHENOLOXIDASES (PPO)

Phenolases, PPO Copper-containing enzyme Oxidizes phenolic compounds to o-quinones: Catalyze conversion of mono-phenols to o-diphenols In all plants; high level in potato, mushrooms, apples, peaches,

bananas, tea leaves, coffee beans

Tea leaf tannins

CatechinsProcyanidins PPO o-Quinone + H2OGallocatechins O2

Catechin gallates

Colored products

Worthington Enzyme Manual

http://www.worthington-biochem.com/index/manual.html

Functional Proteins

Protein FunctionalityHydrodynamic-Aggregation

Viscosity, Elasticity, Viscoelasticity Solubility, Water holding capacity

Hydrophobic- Surface Active Emulsion and foam stabilization Flavor binding

Concentration

Vis

cosi

ty

Dilute

Sem

i-di

lute

Con

cent

rate

d

Hydrodynamic Functionality

Viscosity A property of liquids Viscosity is the resistance to flow. The amount of

energy you need to expend to get a given flow rate.

Stress (force per unit area) is proportional to rate of strain (i.e., flow rate)

Particles of any type in a fluid will increase its viscosity

Large, well hydrated polymers contribute most to viscosity

Elasticity A property of solids Elasticity is the force to achieve a given

percentage change in length Stress (force per unit area) is proportional to strain

(fractional deformation) An elastic material must have some solid-like

network throughout the structure The more load bearing structures the more elastic The more inter-structure links the more elastic

ViscoelasticityMany materials simultaneously show solid

and liquid like properties If they are stretched they will partly and

slowly return to their original shape Elastic solids would completely recover Viscous liquids would retain their shape

Water BindingWater Binding Gels contain pores Water can flow out of

the pores If the gel contracts it

may expel liquid SYNERESIS

Due to closer association of protein with protein

pH

1 2 3 4 5 6 7 8

Sol

ubili

ty /%

0

20

40

60

80

100

SolubilityEmulsoid

Suspensoid

Whey vs. Casein Dense, ordered

globular proteins

2D Gel

Loose, disordered, flexible chains

Loop-train-tail model

Practical Applications

A quick stroll through the literature…

WH= whole hydrolysate

Story Behind the Story Amy-Acrylamide

Andrea-Maillard ingredients

Effect of Citric Acid and Glycine Addition on Acrylamide andFlavor in a Potato Model System

Class discussion;

Bianca and Cassie

A quick review

Protein Analysis Methods