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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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