FOOD FOOD CHEMISTRY: CHEMISTRY:
Unit-2Unit-2StarchStarch
BYBY
DR BOOMINATHAN Ph.D. DR BOOMINATHAN Ph.D. M.Sc.,(Med. Bio, JIPMER), M.Sc.,(FGSWI, Israel), Ph.D (NUS, SINGAPORE)M.Sc.,(Med. Bio, JIPMER), M.Sc.,(FGSWI, Israel), Ph.D (NUS, SINGAPORE)
PONDICHERRY UNIVERSITYPONDICHERRY UNIVERSITY
III lectureIII lecture
8/August/20128/August/2012
Source: Collected from different sources on the internet and presented by Dr Boominathan Ph.D.
StarchStarch
Thanks to Dr. EricksonThanks to Dr. Erickson
Central Washington Central Washington University, USAUniversity, USA
What is it?What is it?
Complex carbohydrate made up Complex carbohydrate made up of two componentsof two components
Components:Components:– AmyloseAmylose– AmylopectinAmylopectin
Properties depend Properties depend on amounts of on amounts of the componentsthe components
Where is it found?Where is it found?
Roots/TubersRoots/Tubers– PotatoPotato– ArrowrootArrowroot– TapiocaTapioca
CerealCereal– CornCorn– Waxy cornWaxy corn– WheatWheat– RiceRice– Waxy riceWaxy rice
Amaranth starch(Bar: 1 µm)
Arrowroot starch(Bar: 20 µm)
Buckwheat starch(Bar: 5 µm)
Cassava starch(Bar: 10 µm)
Corn starch(Bar: 10 µm)
Oat starch(Bar: 5 µm)
Potato starch(Bar: 50 µm)
Rice starch(Bar: 2 µm)
AmyloseAmylose
Linear Linear component of component of starchstarch
Contains Contains 1,4-1,4-alpha-glucosidic alpha-glucosidic bondsbonds
Molecular Molecular weight: weight: less less than 0.5 millionthan 0.5 million
Can form Can form coils coils which will trap which will trap iodineiodine and turn and turn blueblue
AmylopectinAmylopectin
Branched Branched component of component of starchstarch
Contains Contains 1,4-1,4-alpha-glucosidic alpha-glucosidic as as well as well as 1,6-alpha-1,6-alpha-glucosidic bondsglucosidic bonds
Molecular weight: Molecular weight: 50-500 million50-500 million
Limited coiling Limited coiling causes causes purplish-purplish-red colorred color when when iodine addediodine added
Amylose vs. Amylose vs. AmylopectinAmylopectin Starches usually contain Starches usually contain more more
amylopectin than amyloseamylopectin than amylose Generally Generally roots/tubers contain roots/tubers contain
more amylopectinmore amylopectin than than cerealscereals Roots/Tubers: 80% amylopectinRoots/Tubers: 80% amylopectin Cereals: 75% amylopectinCereals: 75% amylopectin Waxy corn Waxy corn andand rice rice contain contain
virtually virtually all amylopectinall amylopectin
Starch CompositionStarch Composition
Starch % amylose % amylopectin Tapioca 17% 83% Potato ~20% ~80% Wheat 25-26% ~75% Corn 24-28% ~75 Waxy corn ~0% ~100% Hi amylose Rice
~ 75% 22%
~ 25% 78%
Starch GranuleStarch Granule
Made in the cytoplasm of plant Made in the cytoplasm of plant cellscells
Amylopectin forms in Amylopectin forms in concentric concentric circles circles with with amyose dispersed in amyose dispersed in betweenbetween
Held together by Held together by hydrogen bondshydrogen bonds The granule swells when heated in The granule swells when heated in
waterwater
Starch GranuleStarch Granule
FunctionsFunctions
GelatinizationGelatinization– Structure in baked productsStructure in baked products– Thickener in sauces, soups, and Thickener in sauces, soups, and
dressingsdressings DextrinizationDextrinization GelationGelation
– Pie fillingPie filling
GelatinizationGelatinization
When starch is heated in waterWhen starch is heated in water Hydrogen bonds break, Hydrogen bonds break, allowing water to allowing water to
enter the granule and the granule swellsenter the granule and the granule swells Amylose migrates out of the granuleAmylose migrates out of the granule H-bonding between H-bonding between water and water and
amylopectin increasesamylopectin increases Reduced free water changes the Reduced free water changes the viscosity viscosity
of the starch mixtureof the starch mixture, thickening it, thickening it
5 % Corn Starch, 30C 5 % Corn Starch, 50C
5 % Corn Starch, 60C 5 % Corn Starch, 70C
Gelatinization and Gelatinization and TemperatureTemperature Gradually thicken with Gradually thicken with
temperaturetemperature Can be heated to 100Can be heated to 100ooC without C without
much granule rupturemuch granule rupture If held at 95If held at 95ooC will implode and C will implode and
lose viscositylose viscosity
Gelatinization and Gelatinization and Type of StarchType of Starch
Best Best thickening thickening ability (TA)ability (TA): potato : potato starchstarch
Worst thickening Worst thickening ability: wheat starchability: wheat starch
More More amylopectin=TA amylopectin=TA more more translucent=more translucent=more stringystringy
Viscosity and Type of Viscosity and Type of StarchStarch
Gelatinization and Gelatinization and SugarSugar Used together in pie fillings and puddingsUsed together in pie fillings and puddings Sugar competes with the starch for water so Sugar competes with the starch for water so
less water available for gelatinizationless water available for gelatinization Delays gelatinization and decreases Delays gelatinization and decreases
viscosityviscosity Increases gelatinization temperatureIncreases gelatinization temperature The more sugar added, the longer the delayThe more sugar added, the longer the delay Disaccharides have a stronger effect than Disaccharides have a stronger effect than
monosaccharidesmonosaccharides
Gelatinization and AcidGelatinization and Acid
Used together in fruit pie fillings, Used together in fruit pie fillings, specifically lemon fillingsspecifically lemon fillings
Acid breaks down starch Acid breaks down starch molecules so the paste is thinnermolecules so the paste is thinner
Decreases viscosityDecreases viscosity Acid effect can be minimized by Acid effect can be minimized by
adding after gelatinization or adding after gelatinization or heating rapidlyheating rapidly
GelationGelation
As a starch paste cools, a gel is As a starch paste cools, a gel is formedformed
Free amylose molecules lose energy Free amylose molecules lose energy as the temperature decreases and as the temperature decreases and form hydrogen bondsform hydrogen bonds
The The bonds create a network that bonds create a network that holds the swelled granules in placeholds the swelled granules in place
Gelation and Starch Gelation and Starch SourceSource The The more amylopectin (less more amylopectin (less
amylose), the softer the gelamylose), the softer the gel Potato starchPotato starch=high =high
amylopectin=good thickening amylopectin=good thickening agent=agent=softsoft gelgel
Corn starchCorn starch=less =less amylopectin=less effective amylopectin=less effective thickening agent=thickening agent=strong gelstrong gel
Gelation and Other Gelation and Other EffectsEffects HeatingHeating
– If temp. too high, will burst, if temp too low, limited amylose If temp. too high, will burst, if temp too low, limited amylose releasedreleased
– Enough amylose needs to be released from the Enough amylose needs to be released from the granule without the granule burstinggranule without the granule bursting
– Moderate temperature and rate of heatingModerate temperature and rate of heating AgitationAgitation
– Agitation during cooling disrupts amylose networkAgitation during cooling disrupts amylose network– Should mix flavorings immediately after removing Should mix flavorings immediately after removing
from heatfrom heat– If stir while heating too much, will break up granules and get If stir while heating too much, will break up granules and get
weakened gel.weakened gel.
Gelation and Other Gelation and Other EffectsEffects Sugar (addition of)Sugar (addition of)
– Decreases gelatinization and Decreases gelatinization and amylose releaseamylose release
– Softer gelSofter gel Acid (addition of)Acid (addition of)
– Decreases gelatinization by Decreases gelatinization by hydrolysis of granuleshydrolysis of granules
– Softer gelSofter gel
Aging GelsAging Gels SyneresisSyneresis (happens due to aging and when cut a gel and (happens due to aging and when cut a gel and
water leaks out)water leaks out)– Loss of water from a gelLoss of water from a gel– Amylose molecules pull together, squeezing water Amylose molecules pull together, squeezing water
outout RetrogradationRetrogradation
– Realignment of amylose moleculesRealignment of amylose molecules– Heat breaks the H-bonds holding the amylose and lets Heat breaks the H-bonds holding the amylose and lets
them move within the gelthem move within the gel– Hydrogen bonds break and reform into more orderly Hydrogen bonds break and reform into more orderly
crystalscrystals– Can be reversed by gently heatingCan be reversed by gently heating– Examples: refrigerated pudding, stale breadExamples: refrigerated pudding, stale bread
DextrinizationDextrinization
When starch is heated without When starch is heated without waterwater
A higher temperature is reached A higher temperature is reached than with waterthan with water
Bonds break throughout the Bonds break throughout the starch forming dextrinsstarch forming dextrins
Genetically-modified Genetically-modified StarchesStarches Waxy starchWaxy starch
– High in amylopectinHigh in amylopectin– Used in fruit pies because thickens well, but does Used in fruit pies because thickens well, but does
not gel wellnot gel well– Have good freeze-thaw stabilityHave good freeze-thaw stability
High amylose starchHigh amylose starch– Amylose creates strong bonds to form strong gelsAmylose creates strong bonds to form strong gels– Used in edible films to coat foodUsed in edible films to coat food– Edible films used in cough drops, candy, coatings for Edible films used in cough drops, candy, coatings for
deep fried potatoes, produce, baked productsdeep fried potatoes, produce, baked products
How to compare How to compare starches?starches? Line spread test:Line spread test:
– Measures thickening powerMeasures thickening power– Poor heated starch into cylinder, lift Poor heated starch into cylinder, lift
cylinder and measure spread after cylinder and measure spread after specified time using concentric circlesspecified time using concentric circles
Universal Texture Analyzer:Universal Texture Analyzer:– Measures gel strengthMeasures gel strength
Percent sag:Percent sag:– Measures gel strengthMeasures gel strength– Measure molded gel height and compare Measure molded gel height and compare
to unmolded gel heightto unmolded gel height– Stronger gel=small % sag, weaker Stronger gel=small % sag, weaker
gel=large % saggel=large % sag
Modified StarchesModified Starches Physically or chemically modifying native Physically or chemically modifying native
starchesstarches Are used for specific applications in the Are used for specific applications in the
food industry, Why?food industry, Why? Native starches have undesirable Native starches have undesirable
qualities:qualities:– Poor processing tolerance to heat, shear and Poor processing tolerance to heat, shear and
acidacid– Poor texturesPoor textures– Do not store, hold, and freeze/thaw wellDo not store, hold, and freeze/thaw well
* Poor processing to heat/shear/acid: due to granules bursting which decreases viscosity
* Freeze/thaw: has to do with amylose binding
Pre-gelatinized Pre-gelatinized StarchesStarches Use:Use:
– Instant puddingInstant pudding Dehydrated gelatinized starchDehydrated gelatinized starch
– Heated so granule swells and then Heated so granule swells and then dehydrateddehydrated
– Swells when water added, no heat Swells when water added, no heat necessarynecessary
– Decreases preparation timeDecreases preparation time– Physical changePhysical change
Thin-Boiling StarchesThin-Boiling Starches
Use:Use:– Pass freely through pipesPass freely through pipes
Acid-hydrolyzed starchAcid-hydrolyzed starch– Hydrolyzes 1,6-alpha-glucosidic bondsHydrolyzes 1,6-alpha-glucosidic bonds– Amylopectin in smaller piecesAmylopectin in smaller pieces– Decreases thickening power, but Decreases thickening power, but
makes a strong gel because hydrogen makes a strong gel because hydrogen bonds form more readilybonds form more readily
Cross-linked StarchCross-linked Starch
Use:Use:– Increases storage time because of reduced Increases storage time because of reduced
retrogradationretrogradation (eg., refrigerated puddings) (eg., refrigerated puddings) – More stable at high temperature, with More stable at high temperature, with
agitation, and with acid additionagitation, and with acid addition– Salad dressings, baby foods, pie fillingsSalad dressings, baby foods, pie fillings
Cross-linked starch moleculesCross-linked starch molecules– Alter hydroxyl ends under alkaline conditions Alter hydroxyl ends under alkaline conditions
by acetic anhydride, succinic anhydride, or by acetic anhydride, succinic anhydride, or ethylene oxideethylene oxide
– Amylose doesn’t realign b/c altered hydroxyl group Amylose doesn’t realign b/c altered hydroxyl group doesn’t line up well. Cross-links amylosedoesn’t line up well. Cross-links amylose
Viscosity and Cross-Viscosity and Cross-linked Starcheslinked Starches
Resistant StarchResistant Starch
Small intestine is unable to digest, limited Small intestine is unable to digest, limited digestion in large intestinedigestion in large intestine
ClassificationsClassifications– RS1: trapped in cells (seeds/legumes)RS1: trapped in cells (seeds/legumes)– RS2: native starch (raw potatoes, bananas, waxy RS2: native starch (raw potatoes, bananas, waxy
maize)maize)– RS3: crystalline, non-granular starch (cooked RS3: crystalline, non-granular starch (cooked
potatoes)potatoes)– RS4: chemically modifiedRS4: chemically modified
Can contribute fiber to food without the fat Can contribute fiber to food without the fat that bran hasthat bran has
Takes up less water than other fiber, making Takes up less water than other fiber, making dough less stickydough less sticky
Smooth even textureSmooth even texture Less than 3 cal/gLess than 3 cal/g