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Angela Chen

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?.

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Angela Chen

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  1. Angela Chen

  2. Sweeteners from Starch….

  3. Sweeteners from Starch….

  4. Sweeteners from Starch….

  5. Sweeteners from Starch….

  6. Sweeteners from Starch….

  7. Sweeteners from Starch….

  8. Hydrocolloids Binding water with carbohydrates

  9. Starches- Our #1 Hydrocolloid? • Hydrocolloidsare 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

  10. Small versus Large • Small 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

  11. AMYLOSE • Linear polymer of glucose • α 1 - 4 linkages • Digestable by humans (4 kcal/g) • 250-350 glucose units on average • Varies widely • Corn, wheat, and potato starch • ~10-30% amylose

  12. AMYLOPECTIN • Branched chain polymer of glucose • α 1 - 4 and α 1 - 6 glycosidic linkages • Mostly digestible by humans • 1,000 glucose units is common • Branch points every ~15-25 units

  13. Starch • Amylose 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% amylopectin • Sugary “mutant” starches have more amylose

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

  15. Starch

  16. 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.

  17. 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

  18. 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.

  19. Gelatinization Starch grains swell when heated in water

  20. H-bonds break, amylose can spill from the grain

  21. Gains may loose integrity Gelatinization is done

  22. During cooling, junction zones form Between amylose and amylopectin

  23. water water water water water water Water is trapped Forming a gel.

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

  25. Starch Modifications • Cross-linking (common modification) • Alkali treatment (pH 7.5-12) with salt • Phosphorus oxychloride • Sodium trimetaphosphate • Adipic and acetic anhydride • Starch phosphates formed after neutralization

  26. Cross-Linking • Resists viscosity breakdown • Resists prolonged heating effects • Resists high shear rates • Resists high acid environments • Increased viscosity • Increased texture

  27. Starch Modifications • Starch 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

  28. Starch Modifications • Oxidation 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

  29. Polysaccharide Breakdown Products

  30. Hydrolytic Products • Maltose • Maltitol • Maltodextrins • Dextrins • Dextrans • Maltose = glucose disaccharide • Maltitol = example of a “polyol” • Maltodextrins = enzyme converted starch fragments • Dextrins = starch fragments (α-1-4) linkages produced by hydrolysis of amylose • Dextrans = polysaccharides made by bacteria and yeast metabolism, fragments with mostly α (1 - 6) linkages

  31. Maltodextrins and enzyme-converted starch: STARCH fermentation SUGARS ETHANOL MODIFIED STARCHES GELATINIZED STARCH alpha amylase Maltodextrins Corn Syrups Sugars

  32. 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 DE Syrup

  33. Dextrinization • A 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

  34. Hydrocolloids Binding water with carbohydrates “Gums”

  35. “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

  36. FUNCTIONS IN FOOD • Gelation • Viscosity • Suspension • Emulsification and stability • Whipping • Freeze thaw protection • Fiber (dietary fiber) • Gut health • Binds cholesterol

  37. 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

  38. “Structural” Polysaccharides Cellulose • Polymer of glucose linked ß-1,4 Hemicellulose • Similar to cellulose • Consist of glucose and other monosaccharides • Arabinose, xylose, other 5-carbon sugars Pectin • Polymer of galacturonic acid

  39. MODIFIED CELLULOSES • Chemically modified cellulose • Do not occur naturally in plants • Similar to starch, but β-(1,4) glycosidic bonds • Carboxymethyl 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

  40. 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

  41. 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.

  42. BETA-GLUCANS • Extracts from the bran of barley and oats • Long glucose chains with mixed ß-linkages • Very 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

  43. 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 .

  44. Others CHITIN • 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

  45. Paper Review Producing fructo-oligosaccharides: For Tuesday

  46. Starch • Starch 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

  47. Starch • Starch suspensions are not stable to heating • Swollen starch granules break down in hot, stirred or acidic conditions • Combinations (ie. heat and acid) will depolymerize • Cross-linking can help stabilize and slow or maybe prevent breakdown

  48. 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.

  49. “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

  50. FUNCTIONS IN FOOD • Gelation • Viscosity • Suspension • Emulsification and stability • Whipping • Freeze thaw protection • Fiber (dietary fiber) • Gut health • Binds cholesterol

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