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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?. - PowerPoint PPT Presentation
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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