Presentation on theme: "Starch Widely used as a food ingredient for many purposes."— Presentation transcript:
1 Starch Widely used as a food ingredient for many purposes. A very wide selection of starches, both native and modified (National Starch has >200 different starches for sale for selected application)Starch gelation and pasting characteristics altered by other ingredients and by processing conditions
3 Starch FormsStarch is the primary carbohydrate source for growing seeds and leaf tissue development and is found in leaves, tubers, fruits and seeds.Two general types of starch exist – amylose and amylopectin. Both are polymers of glucopyranose molecules, but differ in structure and functional properties,
4 Characteristics of Amylose and Amylopectin Characteristic Amylose AmylospectinFormEssentially linearBranchedLinkage-1,4 (some -1,6)-1,4; -1,6Polymer units200-2,000Up to 2,000,000Molecular weightGenerally <0.5 millionmillionGel formationFirmNon-gelling to soft
10 Crystal Structure Forms The form depends upon the source of the granules.Type A crystal structure is found in most cereals, whereasType B is found in some tubers and high amylose cereal starches.Some plants have both A and B and are desginated Type C. When starches are heated in the presence of lipid, a different crystal structure may be formed, which is called Type V.
11 Types of crystal structure in amylopectin (Chaplin, 2004).
12 Native StarchesThe most common native starches are corn (maize), rice, wheat, potato, tapioca (cassava) and waxy maize.Except for waxy maize, these starches generally contain from 15-27% amylose.Waxy maize and other waxy native starches generally contain less than 2% amylose.High amylose starches contain more than 30% amylose and have quite different properties. They: Are difficult to gelatinise > 100° CCan form films and fibres Have more helical structure - may entrap fatty acids – retardsgranule swelling
13 Differences in Native Starches Vary in amylose and amylopectin contentVary in crystal structureVary in gelation and pasting characteristicsVary in minor components that can be incorporated within the structure of amlyose and amylopectinPhoshate estersPhospholipidsProteins
14 Properties of selected commercial starches (National Starch) Viscosity, mild heat, neutralViscosity, high heat, acidicShear resistanceFreeze-thaw stabilityCommentsTapioca (N)35Bland flavoured, fillings and canned2Process tolerant, short texture; dairy products, soups and saucesTapioca (CL)46High viscosity, dairy productsPotatoRapid hydration, high viscosity; meat, sauces snacksCornProcess tolerant, low hot viscosity; dressings and cerealsWaxy maize, cross linkedFreeze thaw stability; frozen foods, fillings and sauces
15 Types of Food Starches Unmodified Native starches: Corn, wheat, etc. Pregelatinized starchesModifiedAcid thinned - hydrolyze to reduce molecular weightCrosslinked - Chemically linking OH's from two adjacent molecules. Toughens granule. Adds acid and heat stabilityDerivatized - Add bulky groups to starch to reduce retrogradation. Changes hydrophobicityCrosslinked-Derivatized - Does bothOxidized - reduces retrogradation.
17 Cross-linked starches make up about 25% of all starches used in foods Cross-linked starches make up about 25% of all starches used in foods. The four major cross-linking agents are shown in Table 7. In addition to different cross-linking agents, the degree of cross-linking varies. The details of the cross-linking of commercial starches remain proprietary to the company making the starch.Table 7: Cross-Linking Agents for StarchEpichlorhydrinStarch - O-CH2-CHOH-CH2-O-StarchSodium TrimetaphosphateStarch - O-P-O-StarchPhosphorus OxychlorideReagentDerivativeAcroleinStarch-O-CH2-CH2-C-O-Starch
18 Cross-linked starches make up about 25% of all starches used in foods Cross-linked starches make up about 25% of all starches used in foods. The four major cross-linking agents are shown below. In addition to different cross-linking agents, the degree of cross-linking varies. The details of the cross-linking of commercial starches remain proprietary to the company making the starch.Reagent DerivativeEpichlorohydrin Starch - O-CH2-CHOH-CH2-O-StarchSodium Trimetaphosphate Starch - O-P-O-StarchPhosphorus Oxychloride Starch - O-P-O-StarchAcrolein Starch-O-CH2-CH2-C-O-Starch
19 Derivitized Starches The five primary derivatized starches, the derivatising agents and the degree of substitution are shown in the following table. The starch properties will vary with the type of derivatised starch and the degree of substitution. Many companies made “double derivatized” starches that are both cross-linked and derivatized.
21 Gelatinization and Pasting “Starch gelatinisation is the collapse (disruption of molecular order) within the starch granule, manifested in irreversible changes in properties such as granular swelling, native crystalline melting, loss of birefringence and starch solubilisation. The point of initial gelation and the range over which it occurs is governed by the starch type, concentration, method of observation, granular type and heterogeneities within the granule population under observation.”“Pasting is the phenomenon following gelatinisation in the dissociation of starch. It involves granular swelling, exudation of molecular components from the granule; and eventually the total disruption of the granules”
22 Factors Affecting Hydration Amount of water Availability of water Time and Temperature of heating Starch type Corn vs. rice etc. Crosslinking Derivitization PregelatinizationpH Saturated monoglycerides
23 ProblemsFailure to hydrateRetrogradationAmylasesLoss of viscosity
26 Pasting characteristics of different native starches (from Food Additives, 2nd Ed 2002, Brane et al. Eds)
27 Gelatinization of starches Type % Amylopectin % Amylose Gelatinization Range °C Granule Size mCornWaxy CornHigh AmylosePotatoRiceTapiocaWheat
28 Paste Properties of Native Starches Starch Type Viscosity Clarity Gel Shear StabilityCereal Regular Short Opaque Strong GoodWaxy Long Clear V Weak PoorRoot, tuber Clear-opaque Weak PoorHigh Amylose V Short V Opaque V Strong Stable
29 Summary of cornstarch paste properties TypeCommentsNativePoor freeze thaw stabilityHigh amyloseGranules- birefringentAcid modifiedDecreased hot paste viscosityHydroxy-ethylIncreased paste viscosity - low retrogradationPhosphateReduced gel at refrigeration temperature - low retrogradationCross-linkedReduced peak viscosity, increased stability; freeze thaw stabilityAcetylatedGood paste clarity and stability
30 Exogenous and Endogenous Effects on Starch Pasting Characteristics AcidpHSugarLipidsProteinsShear
34 Processing Effects Processes that are known to affect the pasting characteristics of starches include:· Order of addition of ingredients· Temperature achieved· Rate of temperature rise· Duration of heating· Rate of cooling· Storage temperature· Shear
35 RetrogradationSolubilised starch polymer and remaining insoluble granular fragment tend to re-associate after heating. The re-associating is termed “Retrogradation”.Retrogradation has been defined as follows:“Retrogradation is a process which occurs when starch chains start to re-associate into an ordered structure. In its initial phase, two or more starch chains may form a simple junction point, which then may develop into more extensively ordered regions. Ultimately, under favourable conditions, a crystalline order appears.”Generally, amylose-containing starches show greater retrogradation. Factors relating to retrogradation include:
36 Factors relating to retrogradation include: · Amount of branching· High amylopectin starches - e.g., waxy maize shows no retrogradation when frozen· Hydrogen bonding between OH groups in amylose in gelatinised starches during cooling· Water forced out of gel structure (syneresis) &Starch insolubilized.
37 Amylopectin also plays a role in retrogradation over time Amylopectin also plays a role in retrogradation over time. Short-term retrogradation is largely associated with amylose (which reaches a limit in 2 days), whereas long-term retrogradation is thought to involved amylopectin (reaching a limit is 40 days)The botanical source is important in respect to retrogradation, not only for starches that differ in amylose content, but also for starches with very similar amylose content.For retrogradation to occur there must first be an aggregation of the chains.Amylopectin from potato and tapioca (B type starches) retrograde to different degrees and this has been related to difference in short branch chains.
38 Puddings, sauces, pie fillings Functions of starch in food systems and examples of how these are utilised in different food systems.FunctionExampleThickenerPuddings, sauces, pie fillingsBinderFormed meats; breaded items; pastaGelling agentsConfectionsEncapsulation, Emulsion StabilizerFlavours, bottlers emulsionsCoatingCandies, glazes, icings and toppingsWater BinderCakesFree Lowing/Bulking AgentBaking powderReleasing AgentCandy makingTexture modifierProcessed cheese, meat productsFat ReplacerSalad dressings, dairy products, baked goods
39 ApplicationsThe amount of starch used in different types of foods ranges from 0.2% in beverage products to 12% is some candies. Use levels, except for gums & candies, generally fall into two general categories.<1%: beverages, butter sauces, cake mix and icing and marshmallows2 – 5%: baby foods, spoonable salad dressings, Harvard style beets and creamed soups, cheese analogs
42 In the selection of a starch for a food application, consideration needs to be given to: · Flavour· Texture· Body· Appearance
43 In the selection of a starch for a food application, consideration needs to be given to: FormulationHow long is the shelf life of the foodHigh Acid or Low AcidProcessing conditionsHigh heat vs low heatHigh shear vs low shearBoth high heat and high shear
44 Other Questions to ask in Selecting a Starch Is there sufficient moisture to hydrate the starch?· Is the solids level to low or too high?· How will lipids affect the starch and the resultingfood?· What salts and what salt levels are required inthe food?· What type and level of sugar is being used?· Are there other hydrocolloids included in theformulation?
45 Source, type, application, function and benefits of some starches in selected foods. OriginTypeApplicationFunctionBenefitCornNativeSoup mixesThickenerBody, mouth feelPre-gelledPuffed snacksTextureImproved processingWaxy maizeCross linkedSalad dressingStabiliserBody, gloss, stabilityTapiocaCold water swellingInstant dairy productsBland flavour, premium cook up texturePotatoNative, cook upDry mixesRapid hydration, high viscosity
46 Starch types for different foods and applications BindingViscosity buildingFilm formationTexturisingSoups and sauces-X, XS, PX, PXS--BakeryPNX, P, PX, PXSD, MP, X, PX, PXS, MDairyN, A, M,X, XS, P, PX, PXSX, XS, PXS, A, NX, O, PO, MSnacksN, P, PN, PO, D---Batters & coatingsX, PX, OP, PXDO, PO, D. MMeat productsN, X, XS, P----XSN=native; X = cross-linked; P=pregelatinised; S=substituted (derivatised); O=oxidised; A=acid hydrolysed;D=dextrin; M=maltodextrin. Where letters are together without a comma, all types are combined into a single product.
47 Selection of starches for dairy foods ProductRequirementsBest Starch TypeCommentsGeneral DairyHeat tolerant, shear tolerant, freeze-thaw stable, bland flavourCross-linked and substitutedTapioca best from a flavour viewpointUHT productsMore heat & shear tolerantIncrease degree of cross-linkingFrozen dessertsFreeze-thaw stability most importantSubstitutedFat replacers in low fat products, cross-linked for better freeze thaw stabilityDry mix applicationsPerform under low heating conditionsPregelled, low level of cross-linking, freeze- thaw stabilityInstant puddings and cheese sauces most common usageYoghurtAcid stableCross-linkedUsed to minimise syneresisProcessed cheeseGelling characteristicsCross-linked waxy maize
48 Common problems, causes and possible solutions for dairy foods Possible causesPossible solutionsSyneresisPoor freeze thaw stability; colloid system breakdownDecrease shear; Increase starch level, Increase cooking time and/or temperature; Use stabilised starchRunny textureLow solids contentIncrease starch; select different starch; decrease shear; check for amylases in other ingredientsGraininessStarch not cookedConsider pregelled starch. Adjust water; adjust processing time and/or temperature
49 Selection of starches for extruded products RequirementsBest Starch TypeCommentsCereals“Bowl” stabilityHigh amylose starchExpanded snacksGood expansionLight to moderate cross- linked starch“Half” productShear stabilityPregelled, cold water swelling, moderate cross linkedSingle screw extrusion followed by bakingTwin screw extruded productsShear, pressure and temp. stabilityCross linked “cook-up” starches
50 Common problems, causes and possible solutions for extruded products Possible causesPossible solutionsLack of crispnessWeak expansionIncrease amylose if product exposed to high shearPoor cutting or shapeLow dough viscosity or strengthIncrease amylosefor high shear; Increase amylopectin for low shear adjust moisture contentNon-uniform sheet thicknessHigh water absorptionDecrease water content; choose starch with low water holding capacity
51 Selection of starches for meat products RequirementsBest Starch TypeCommentsBologna & frankfurtersHigh viscosity, high water holding capacityLightly or moderately cross linked and substitutedneed to have products that are freeze/thaw stableSurimi, cold applicationsHigh water holding capacityBlends of native and modified amylose- containing starchesUsed as a filler; blends used to improve moistness of the gelSurimi, hot applicationsBlends of native and modified waxy starchUsed as a filler; blends used to improve gel moistness
52 Common problems, causes and possible solutions for meat products Possible causesPossible solutionsPoor water holding capacityLack of water-binding componentsAdd substituted, stabilised starch; use starch with high water binding capacityLow freeze-thaw stabilityLow level of modificationIncrease degree of cross linking and or substitutionPoor bite, soft textureStructure not fully developedCheck starch selection; add substituted, stabilised starch
53 Take Home Starches are very complex Selection of a starch is related to the type of food and processing conditionsLots of choices – different starches (both native and modified) give different characteristics to the foodModified starches generally used when you need:Resistance to shearResistance to heatResistance to acidReduced retrogradationProduct expected to have a very long shelf-life