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Chapter 3 Carbohydrates 1 Learning Objectives 1. 2. 3. 4. 5. 6. Identify the functions of carbohydrates List important monosaccharides and disaccharides and give examples of foods in which each is found Identify foods high in natural sugars, added sugars, and fiber List the potential health risks of consuming too much added sugar Identify food sources of starch and list the uses of starch in cooking Distinguish between the two types of dietary fiber and list examples of food containing each one Learning Objectives (cont’d) 7. 8. 9. 10. 11. 12. Describe the health benefits of a high-fiber diet Describe how carbohydrates are digested, absorbed, and metabolized by the body State the dietary recommendations for carbohydrates Identify foods as being made from whole grains or refined grains Discuss the nutritional value and use of grains and legumes on a menu Recognize alternatives to sugar in foods Photosynthesis Plants can make their own carbohydrates from the carbon dioxide in the air and water taken from the soil. Photosynthesis converts energy from sunlight into energy stored in carbohydrates, which the plants uses to grow and be healthy. 4 Functions of Carbohydrate Functions as primary source of body’s energy Central nervous system and red blood cells rely almost exclusively on glucose Glucose is stored in liver and muscles as glycogen Spares protein from being burned for energy Helps body burn fat efficiently Part of various materials in body, such as connective tissue, some hormones & enzymes, and genetic material 5 Functions of Carbohydrate (cont’d) Fiber Promotes normal functioning of intestinal tract Lowers blood cholesterol You need at least 100 – 150 grams of carbohydrate daily to spare protein and fat from being burned for fuel and to provide glucose to the central nervous system and red blood cells Categories of Carbohydrate Simple carbohydrates Natural sugars Added (Refined) sugars Complex carbohydrates (polysaccharides) Starch Fiber 7 Monosaccharides and Disaccharides 8 Relative Sweetness of Sugars and Artificial Sweeteners Sweetener Rating Sugars Lactose 20 Glucose 70 – 80 Sucrose 100 High-fructose corn syrup Fructose 120 – 160 140 Artificial Sweeteners Aspartame (Nutrasweet, Equal) Acesulfame-K (Sunette) Saccharin (Sweet ’N Low) Sucralose (Splenda) 160–220 200 200 – 700 600 9 Neotame 7,000–13,000 Added Sugars Added sugars: Sugars added to a food for sweetening or other purposes, do not include natural sugars Examples: Granulated white sugar, brown sugar, high fructose corn syrup 10 Examples of Added Sugars White sugar (sucrose) High-fructose corn syrup or corn syrup Invert sugar Brown sugar Molasses Honey Powdered sugar Raw sugar Demerara sugar 11 Foods with Added Sugars in US Diet Soft drinks Candy Tabletop sugars Baked goods Fruit drinks Ice cream Sugars on the Nutrition Facts Label The number of grams of “Sugars” includes both natural and added sugars To find out if a food contains added sugar, look at the ingredient list 4 grams sugar = 1 teaspoon 13 Added Sugars and Health Dental caries (sugar & starch) Obesity Diabetes Heart Disease Hypoglycemia Hyperactivity in Children 14 Lactose Intolerance An intolerance to milk and most milk products due to a deficiency of the enzyme lactase Symptoms often include flatulence & diarrhea within 30 minutes to 2 hours Especially prevalent among Asian Americans, Native Americans, African Americans, Latinos, and other groups Treatment requires a diet limited in lactose Most people can drink small amounts of milk especially if taken with food 15 Complex Carbohydrate: Starch Made of a long chain of glucoses linked together The glucose chains may be straight (amylose) or branched (amylopectin) Found only in plant foods: grains, legumes, vegetables, some fruits Most starchy foods are cooked to make them flavorful and able to be digested Gelatinization – When starches are heated, they absorb water and swell in size 16 Structures of Starch and Glycogen 17 Fibers Polysaccharides found in plant foods that the body can’t digest or absorb Some fiber is digested by bacteria in the large intestine Two types: 1. soluble or viscous fiber 2. insoluble or nonviscous fiber 18 Food Sources of Fiber Soluble fiber 1. 2. 3. 4. Beans and peas Some cereal grains (barley, oats) Many fruits (apples, pears, grapes, citrus) Many vegetables (carrots) Insoluble fiber 1. 2. 3. 4. 5. Wheat bran, brown rice, whole grains Many vegetables (cabbage, carrots) Many fruits Beans and peas Seeds 19 Health Effects of Fiber Soluble, viscous fiber Traps carbohydrates to slow digestion and absorption of glucose Binds to cholesterol in GI tract Reduces risk of diabetes and heart disease Insoluble, nonviscous fiber Increases fecal weight so that feces travels quickly through the colon Provides feeling of fullness Helps prevent and treat constipation, diverticulosis, and hemorrhoids Helpful in weight management 20 Health Effects of Fiber Reduces risk of type 2 diabetes and helps control diabetes A diet high in fruits, vegetables, beans, and grains that contain soluble fiber can lower blood cholesterol levels and therefore lower the risk of heart disease More research needs to be done on whether fiber helps prevent colon cancer If you decide to eat more fiber….. Do so slowly and Drinks lots of fluids to give time for your intestine to adapt 22 Nutrition Science Focus: Regulation of Blood Glucose Digestion, Absorption, & Metabolism of Carbohydrates Starch digestion begins in mouth. (enzyme- salivary amylase) Before being absorbed, carbohydrates must be broken down into monosaccharides. Enzymes in small intestine (sucrase, lactase, maltase, and pancreatic amylase) ensure that single sugars are absorbed In the liver, fructose and galactose are converted to glucose or further metabolized to make glycogen or fat 24 Dietary Reference Intakes RDA for carbohydrate – 1 year old + 130 grams daily (minimal amount – you really need 2x) AMDR – 1 year old + 45-65% of kcalories AI for total fiber 14 g/1000 kcal Men 19 – 50 years old 38 g Men over 50 years old 30 g Women 19 – 50 years old Women over 50 years old 25 g 21 g DRIs – added sugars < 25% of total kcalories 25 A Kernel of Wheat Whole Grains Examples: Whole wheat Whole rye Oatmeal Whole oats Whole hulled barley Popcorn Brown rice Whole grains offer: More nutrients Phytochemicals More fiber Dietary Guidelines for Americans recommends 3+ servings of whole grains each day 27 Culinary Science Gelatinization Starchy thickeners Flour Cornstarch Arrowroot Potato starch Rice flour Artificial Sweeteners Approved Possibilities Saccharin Alitame Aspartame Cyclamate Acesulfame-K Sucralose Reduced-Kcal Neotame Sweetener Tagatose 29 5. Sugar Replacers or Polyols A group of carbohydrates that are sweet and occur naturally in plants Examples: sorbitol, xylitol found in sugarfree gums and candy 30 5. Sugar Replacers or Polyols Benefits: Don’t provide as many kcalories as sugar – only about 2 kcal/gram Don’t promote tooth decay Taste sweet – though not as sweet as sugar. Add bulk and texture to foods Cause smaller increases in blood sugar and insulin than sugar Side effects 31 Sugar Replacers or Polyols Sugar Replacer Kcal/gram Uses Description* Mannitol 1.6 Chewing gum, powdered foods, chocolate coatings •50 to 70% as sweet as sugar Candies, chewing gum, baked goods, frozen desserts •60% as sweet as sugar. gum, Sorbitol 2.6 •May causes a laxative effect when 20 grams or more are consumed •Does not absorb moisture so it works well as a dusting powder for chewing gum so the gum doesn’t stick to the wrapper baked goods •May cause a laxative effect when 50 frozen desserts grams or more are consumed •Cool, pleasant taste 32 Sugar Replacers or Polyols (cont’d) Xylitol Erythritol Isomalt 2.4 0.2 2.0 Chewing gum, candy •As sweet as sugar Beverages, chewing gum, candy, baked goods •Newest polyol Candies, toffee, fudge, wafers •45 to 60% as sweet as sugar •Pleasant taste •Very heat stable •Much less of a laxative effect than other polyols •Works well with other sweeteners to improve flavor and body •Used to add bulk and sweetness to foods •Very heat stable •Works well with other sweeteners to improve flavor 33 Sugar Replacers or Polyols (cont’d) Lactitol Maltitol 2.0 2.1 Chocolate, candies, cookies and cakes, frozen dairy desserts •30 to 40% as sweet as sugar No-sugar added ice cream, lowcarb bagels, candy, chewing gum, chocolate, baked goods •90% as sweet as sugar •Mild sweetness with no aftertaste •Used to add bulk and sweetness to foods •Works well with artificial sweeteners •Used to add bulk and sweetness to foods 34 Sugar Replacers or Polyols (cont’d) Hydrogenated Starch Hydrolysates 3.0 Candy, baked goods •25 to 50% as sweet as sugar •Used as bulk sweetener in low calorie foods. Performs other functions in foods as well. •Can mask unpleasant off-flavors •Blends well with flavors •Works well with other sweeteners *All sugar replacers have the following characteristics: • Occur naturally • Don’t provide as many kcalories as sugar. The average kcalories per gram is 2, compared with 4 kcalories/gram from sugar. • Don’t promote tooth decay • Cause smaller increases in blood glucose and insulin levels than sugar 35 Stevioside A naturally sweet extract from the leaves of the stevia bush found in South America Approved as GRAS substance – 2008 Glycemic Response How quickly and how high your blood sugar rises after eating Eating mainly foods with a low glycemic response is important for people with diabetes and seems to decrease the risk of heart disease, type 2 diabetes, and colon cancer, as well as enhancing weight management 37 Glycemic Index Glucose Corn flakes Waffles, French-fried potatoes, jelly beans Bagel, white bread White sugar, cantaloupe Raisins, tortilla chips, cola soda, ice cream, pizza Rye bread Orange juice Fresh orange, peas, carrots Fresh peach, old-fashioned oatmeal, apple juice White rice, spaghetti, apple, pear, tomato soup Skim milk, low-fat yogurt Kidney beans Grapefruit Soybeans Peanuts 38 Copyright ©2010 John Wiley & Sons, Inc. 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