Chapter 9 Complex Carbohydrates

Two Names for Complex Carbohydrates

• 1. Polysaccharides- a chain of many sugar units or saccharides

• 2. Macromolecules- very large molecules that contain hundreds or thousands of atoms each

Four Types of Complex Carbohydrates

• 1. Starches

• 2. Cellulose

• 3. Carbohydrate Gums

• 4. Pectin

Cellulose

• A polysaccharide made from large amounts of β-D-glucose

• Some animals use cellulose as a food source

• Humans lack the digestive enzymes to break down cellulose

• Cellulose is a fiber and forms the rigid structure of plants

Carbohydrate Gums

• Polysaccharides that are soluble in water and extracted from plants

• Used to thicken and stabilize mixtures and trap color and flavor by protecting them from moisture absorption, evaporation, or chemical oxidation

• Ex. Gum arabic, karaya gum, gum tragacanth, gum agar, carageenan, algin

Pectin

• Complex carbohydrates that are found in plant cells and made of chemical derivatives of sugar called sugar acids

• Found naturally in fruits• It can produce a strong gel that is stable to near

100ºC• In the presence of sugar, pectin dehydrates, and

acid will thicken pectin• Pectin is a key component in jams and jellies

Functions of Complex Carbohydrates in Food Preparation• 1. Provide structure

• 2. Bind ingredients together

• 3. Act as absorbing agents or thickeners

Providing Structure

• Flour provides the majority of bulk and structure for baked goods and other food products

• Starch is the main component of wheat flour • Starch thickens when heated and gels when

cooled so that foods with starch can take and hold different shapes

• Cellulose provides structure for fruits and vegetables

• Pectins and gums give texture to jams, jellies and ice cream

Binding Agents

• Amylose molecules work better than amylopectin molecules at holding batters to vegetables and meats when they are deep fried

• If the batter-dipped food is allowed to sit for about 20 minutes prior to frying then the binding will be increased

• Carageenan is a gum used to bind cocoa in chocolate milk and stabilizes ice cream and other dairy products

Thickening Agents

• Starch is used to thicken liquids and is usually combined with them in food preparation

• Starch must be heated first to break its intermolecular bonds in order to mix with liquids by forming hydrogen bonds

Examples of Starch Mixtures

• Sols- ex. pancake, waffle, and muffin batter, white sauce and gravy

• Pastes- ex. water or milk combined with starch. This paste can be stirred into hot broth without lumping and is used to thicken soups and stews

• Gels- amylose forms more stable gels than amylopectins

• Slurries- uncooked mixtures of water and starch

Viscosity

• The resistance of a mixture to flow• Viscosity is tested by using line-spread

sheets• Line spread sheets have a sample placed

in the middle of marked lines of concentric circles and however far the sample flows is how viscous the sample is

• Gels are more viscous than pastes, pastes are more viscous than sols

Stability

• The ability of a thickened mixture to remain constant over time and temperature changes

• A stable sauce can be frozen or reheated and still look and taste the same as when first prepared

• Waxy maize starch is a very stable starch

Opacity vs. Translucency

• Opacity- the ability of an object to block light

• Translucency- the measure of how much light can pass through an object

Complex Carbohydrates and Nutrition

• Complex carbohydrates provide 4 calories of energy per gram.

• The brain uses glucose as its energy source

• Cellulose, or fiber, aids in hunger satiety, digestion, and elimination

• Fruits, vegetables, and grains all have fiber

Nutritional Functions of Starches

• Provide energy

• Provide bulk for digestion

• Tie up bile acids and decrease its reabsorption

• Lower blood cholesterol levels and fight atherosclerosis

• Promote the use of fat