1 chapter 3 carbohydrates. learning objectives 1. identify the functions of carbohydrates 2. list...
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Chapter 3
Carbohydrates
Learning Objectives
1. Identify the functions of carbohydrates
2. List important monosaccharides and disaccharides and give examples of foods in which each is found
3. Identify foods high in natural sugars, added sugars, and fiber
4. List the potential health risks of consuming too much added sugar
5. Identify food sources of starch and list the uses of starch in cooking
6. Distinguish between the two types of dietary fiber and list examples of food containing each one
Learning Objectives (cont’d)
7. Describe the health benefits of a high-fiber diet
8. Describe how carbohydrates are digested, absorbed, and metabolized by the body
9. State the dietary recommendations for carbohydrates
10. Identify foods as being made from whole grains or refined grains
11. Discuss the nutritional value and use of grains and legumes on a menu
12. Recognize alternatives to sugar in foods
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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.
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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
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
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Categories of Carbohydrate
Simple carbohydrates Natural sugars Added (Refined)
sugars
Complex carbohydrates (polysaccharides) Starch Fiber
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Monosaccharides and Disaccharides
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Relative Sweetness of Sugars and Artificial SweetenersSweetener Rating
Sugars
Lactose 20
Glucose 70 – 80
Sucrose 100
High-fructose corn syrup 120 – 160
Fructose 140
Artificial Sweeteners
Aspartame (Nutrasweet, Equal) 160–220
Acesulfame-K (Sunette) 200
Saccharin (Sweet ’N Low) 200 – 700
Sucralose (Splenda) 600
Neotame 7,000–13,000
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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
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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
Foods with Added Sugars in US Diet
Soft drinks Candy Tabletop sugars Baked goods Fruit drinks Ice cream
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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
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Added Sugars and Health
Dental caries (sugar & starch)
Obesity Diabetes Heart Disease Hypoglycemia Hyperactivity in Children
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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
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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
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Structures of Starch and Glycogen
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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
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Food Sources of Fiber
Soluble fiber1. Beans and peas
2. Some cereal grains (barley, oats)
3. Many fruits (apples, pears, grapes, citrus)
4. Many vegetables
(carrots)
Insoluble fiber1. Wheat bran, brown
rice, whole grains
2. Many vegetables (cabbage, carrots)
3. Many fruits
4. Beans and peas
5. Seeds
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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
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
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If you decide to eat more fiber…..
Do so slowly and Drinks lots of fluids
to give time for your intestine to adapt
Nutrition Science Focus:Regulation of Blood Glucose
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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
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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 25 g Women over 50 years old 21 g
DRIs – added sugars < 25% of total kcalories
A Kernel of Wheat
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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
Culinary Science
Gelatinization
Starchy thickeners Flour Cornstarch Arrowroot Potato starch Rice flour
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Artificial Sweeteners
Approved Saccharin Aspartame Acesulfame-K Sucralose Neotame
Possibilities Alitame Cyclamate
Reduced-Kcal Sweetener Tagatose
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5. Sugar Replacers or Polyols
A group of carbohydrates that are sweet and occur naturally in plants
Examples: sorbitol, xylitol found in sugar-free gums and candy
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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
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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•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
Sorbitol 2.6 Candies, chewing gum, baked goods, frozen desserts
•60% as sweet as sugar. gum, baked goods•May cause a laxative effect when 50 frozen desserts grams or more are consumed•Cool, pleasant taste
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Sugar Replacers or Polyols (cont’d)
Xylitol 2.4 Chewing gum, candy
•As sweet as sugar•Pleasant taste
Erythritol 0.2 Beverages, chewing gum, candy, baked goods
•Newest polyol•Very heat stable•Much less of a laxative effect than other polyols•Works well with other sweeteners to improve flavor and body
Isomalt 2.0 Candies, toffee, fudge, wafers
•45 to 60% as sweet as sugar•Used to add bulk and sweetness to foods•Very heat stable•Works well with other sweeteners to improve flavor
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Sugar Replacers or Polyols (cont’d)
Lactitol 2.0 Chocolate, candies, cookies and cakes, frozen dairy desserts
•30 to 40% as sweet as sugar•Mild sweetness with no aftertaste•Used to add bulk and sweetness to foods•Works well with artificial sweeteners
Maltitol 2.1 No-sugar added ice cream, low-carb bagels, candy, chewing gum, chocolate, baked goods
•90% as sweet as sugar•Used to add bulk and sweetness to foods
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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
Stevioside
A naturally sweet extract from the leaves of the stevia bush found in South America
Approved as GRAS substance – 2008
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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
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Glycemic IndexGlucose
Corn flakes
Waffles, French-fried potatoes, jelly beans Bagel, white breadWhite sugar, cantaloupeRaisins, tortilla chips, cola soda, ice cream, pizzaRye breadOrange juiceFresh orange, peas, carrotsFresh peach, old-fashioned oatmeal, apple juiceWhite rice, spaghetti, apple, pear, tomato soupSkim milk, low-fat yogurtKidney beansGrapefruit
SoybeansPeanuts
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