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Chemistry of Foods

Chemistry of Foods. Chapter 3. Learning Objectives. •Convert grams of fat, protein, and carbohydrates into kcal Name four carbohydrates and describe their chemical makeup • Classify carbohydrates • Compare the sweetness of various sugars • Name three uses of carbohydrates in foods.

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Chemistry of Foods

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  1. Chemistry of Foods Chapter 3

  2. Learning Objectives •Convert grams of fat, protein, and carbohydrates into kcal • Name four carbohydrates and describe their chemical makeup • Classify carbohydrates • Compare the sweetness of various sugars • Name three uses of carbohydrates in foods

  3. What is nutrition? • Process by which the foods people eat provide the nutrients needed to grow and stay healthy • Nutrients: • Naturally occurring chemical substances found in food • 6 categories: • Proteins • Lipids • Vitamins • Minerals • Water • carbohydrates

  4. What is nutrition? • Kilocalories- energy (kcal) • Proteins • Fats • Carbohydrates • Conversion: • 1 gram of protein or carbohydrate = 4 kcal • 1 gram of fat = 9 kcal

  5. Carbohydrates • Carbohydrates come from plants • Simple: • Different forms of sugar • Monosaccharides & disaccharides • Complex: • Starches and dietary fiber • polysaccharides

  6. Carbohydrates • Named carbohydrates because hydrates of carbon • Composed of hydrogen and carbon • Cn(H2O)n • Major function: provide energy • Although not essential, important in many body functions

  7. Carbohydrate Functions in Food • Flavor enhancing & sweetening • carmelization • Water binding • Contributes to texture • Hygroscopic nature/water absorption • Provides food for yeast • Regulates gelation of pectin dispersing molecules of protein or starch

  8. Carbohydrate Functions in Food • Acts to subdivide shortening for creaming control crystallization • Prevents spoilage • Delaying coagulation protein • Gives structure due to crystals • Affecting osmosis • Affecting color of fruits • Affecting texture (viscosity, structure) • Contributes flavor other than sweetness

  9. Carbohydrate Functions in Food • May have multiple functions • Example: lollipops- • Control crystallization • Gives structures • Flavor enhancer and sweetner

  10. Monosaccharide • 6 carbons • Hexoses • Glucose (aka dextrose), fructose, galactose • 5 carbons • Pentoses • Ribose, deoxyribose

  11. Disaccharides • Two monosaccharides linked together • Sucrose- 1 glucose + 1 fructose • Lactose- 1 glucose + 1 galactose • Maltose- 2 glucose • Linked together by removing water (dehydration) • Broken by adding water back (hydrolysis)

  12. Sweetness • Not all sugars have same sweetness • Cola-type 10-12% sugars • Depends on formula (mix) • Table 3-3 • Several applications in foods • Table 3-1

  13. Sugars in Foods • Color, texture, sweetness • Major role as sweetener • Honey, sorghum/molasses, maple syrup, and selected fruit juice- sweetener substitute for cane and beet sugar • Glucose & fructose are most soluble and enhance browning

  14. Sugars in Foods • Inversion- • Hydrolysis of sucrose into fructose and glucose • AKA invert sugars • Need an enzyme or acid

  15. Carmelization • Process of applying heat • Sugars dehydrate and breakdown • Complex reaction but simple to do • Example: peanut brittle • Once melting point is reached sugar will carmelize • Each sugar as its own melting point

  16. Crystallization • Can be a problem in variety of products • Example: crystallization of lactose • Make nonfat milk difficult to disperse • Make frozen desserts gritty

  17. Crystallization • Candies: • Divided into two groups- • Crystalline and noncrystalline • Crystaline: fudge, donfant, many others • Noncrystaline: caramels, brittles, taffies, marshmallows

  18. Crystallization • Rate of crystallization depends on speed at which nuclei grow into crystals

  19. Crystallization • 4 factors: • Concentration- • More concentrated = faster • Temperature- • Higher temperature = slower • Agitation • Mixing = faster • Impurities- • Fats and protein

  20. Polysaccharides • Combinations of more than 2 sugars = oligosaccharides • If very large called polysaccharides • Added to foods for a variety of reasons • Increase dietary fiber content • Thicken • Starch most common polysaccharide • “Gum” naturally occurring added to food

  21. Polysaccharides-Starch • Starch most common polysaccharide • Made of glucose units linked together • Storage form of energy for plants • Glycogen storage form of energy for animals • Starch forms granules • Vary is size and shape depending on type of plant

  22. Polysaccharides-Starch • Two- types: • Amylose and amylopectin • Amylose = 20-30% of most native starches • Some starches only contain amylopectin • Example: cornstarch

  23. Polysaccharides-Starch • Amylose contributes to gel formation • Reversible up to between 140˚F – 158˚F • Temperature affects gelatinization (irreversible swelling) • Starts between 140˚F – 158˚F • Increase in water absorption • Gelatinization range • Temp. in which all granules are fully swollen

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