Angela Chen

  • View
    45

  • Download
    0

Embed Size (px)

DESCRIPTION

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

Text of Angela Chen

  • Angela Chen

  • Sweeteners from Starch.

  • Sweeteners from Starch.

  • Sweeteners from Starch.

  • Sweeteners from Starch.

  • Sweeteners from Starch.

  • Sweeteners from Starch.

  • HydrocolloidsBinding 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 functionThus, plants store energy into starch granules

  • AMYLOSELinear polymer of glucose 1 - 4 linkagesDigestable by humans (4 kcal/g)250-350 glucose units on average Varies widelyCorn, wheat, and potato starch~10-30% amylose

  • AMYLOPECTINBranched chain polymer of glucose 1 - 4 and 1 - 6 glycosidic linkagesMostly digestible by humans1,000 glucose units is commonBranch points every ~15-25 units

  • StarchAmylose may have a few branched chainsHelical structure with a hydrophobic coreCore may contain lipids, metals, etc.Amylose to Amylopectin ratios ~ 1:4Varies with the plant sourceWaxy starches are ~100% amylopectinSugary mutant starches have more amylose

  • Straight-Chained Starch = AmyloseGlucose polymer linked -1,4 and -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 StarchesGelatinization is the easiest modificationHeated in water then dried.Acid and/heat will form dextrins-Amylasehydrolyzes (1-4) linkagerandom attack to make shorter chains-AmylaseAlso attacks (1 - 4) linkagesStarts at the non-reducing end of the starch chainGives short dextrins and maltoseBoth enzymes have trouble with (1 - 6) linkages

  • Gelatinization of Starch Native starch granules are insoluble in cold water, despite some swellingHeated water increases kinetic energy, breaking some intermolecular bonds, and allows water to penetrateThe 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 typesThere must be enough water to break open and bind to the starch hydrogen binding sites.

  • Starch grains swell when heated in waterGelatinization

  • H-bonds break, amylose can spill from the grain

  • Gelatinization is done

  • Water is trappedForming a gel.

  • WATERAs 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 saltPhosphorus oxychlorideSodium trimetaphosphateAdipic and acetic anhydrideStarch phosphates formed after neutralization

  • Cross-LinkingResists viscosity breakdownResists prolonged heating effectsResists high shear ratesResists high acid environmentsIncreased viscosityIncreased texture

  • Starch ModificationsStarch SubstitutionsAdding monofunctional groupsBlocking Groups added to the starchAcetyl (2.5% max starch acetates)Hydroxypropyl, phosphates, ethersSlows retrogradation (re-association of amylose)Lowers GTR, stabilizes the starch

    Acetate + Starch

  • Starch ModificationsOxidation and BleachingHydrogen peroxideAmmonium persulfateNa/Ca hypochlorite0.0082 lbs chlorine/pound of starchK-permanganateNa-chloriteWhitens the starchRemoves carotenes and other natural pigments ~25% of oxidizers break C-C linages~75% of oxidizers will oxidize the hydroxyl groupsLowers viscosity, improves clarity of gels

  • Polysaccharide Breakdown Products

  • Hydrolytic ProductsMaltoseMaltitolMaltodextrinsDextrinsDextrans

    Maltose = glucose disaccharideMaltitol = example of a polyol Maltodextrins = enzyme converted starch fragments

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

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

  • Maltodextrins and enzyme-converted starch:

    STARCHfermentationSUGARS

    ETHANOL

    MODIFIED STARCHES

    GELATINIZED STARCHalpha amylaseMaltodextrins

    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

    Low DE syrupalpha amylaseMDbeta amylaseHigh DESyrup

  • DextrinizationA non-enzymatic method to product low-molecular weight fragmentsHigh heat treatment of acidified starchPyro-conversion of starch to dextrinsBoth breaks and re-forms bondsWide-range of products formedVary in viscositySolubilityColor (white, yellow)Reducing capacityStability

  • HydrocolloidsBinding water with carbohydratesGums

  • 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 FOODGelationViscositySuspensionEmulsification and stabilityWhippingFreeze thaw protectionFiber (dietary fiber)Gut healthBinds cholesterol

  • STRUCTURAL CONSIDERATIONSElectrical charge, pH sensitiveInteractions with Oppositely charged moleculesSaltsAcidsChain lengthLonger chains are more viscousLinear vs Branched chainsInter-entangled, enter-woven molecules

  • Structural PolysaccharidesCellulosePolymer of glucose linked -1,4HemicelluloseSimilar to celluloseConsist of glucose and other monosaccharidesArabinose, xylose, other 5-carbon sugarsPectinPolymer of galacturonic acid

  • MODIFIED CELLULOSESChemically modified celluloseDo not occur naturally in plantsSimilar to starch, but -(1,4) glycosidic bondsCarboxymethyl cellulose (CMC) most commonAcid treatment to add a methyl groupIncreases water solubility, thickening agentSensitive to salts and low pHFruit fillings, custards, processed cheeses, high fiber filler

  • PECTINSLinear polymers of galacturonic acidGels form with degree of methylation of its carboxylic acid groupsMany natural sourcesSusceptible to degrading enzymesPolygalacturonase (depolymerize)Pectin esterases (remove methyl groups)Longer polymers, higher viscosityLower methylation, lower viscosityIncrease electrolytes (ie. metal cations), higher viscositypH 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 acid.

  • BETA-GLUCANSExtracts from the bran of barley and oatsLong glucose chains with mixed -linkagesVery large (~250,000 glucose units)Water soluble, but have a low viscosityCan be used as a fat replacerResponsible for the health claims (cholesterol) for whole oat productsFormulated 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 response.

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

    Beta-Glucan

  • OthersCHITINPolymer of N-Acetyl-D-glucosamineFound in the exoskeleton of insects and shellfishMany uses in industry, food and non-food.

    INULINChains of fructose that end in a glucose moleculeGenerally a sweet tasteIsolated from Jerusalem artichokes and chicoryAct as a dietary fiberPotentially 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 cookingUseful thickening agentCan be used in dried sauces and salad dressingsUsed 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

  • StarchStarch gels change their properties during storageSlow retrogradation of amylopectin is commonThe 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 pla