Chapter 9 – The Complex Carbohydrates

Chapter 9 – The Complex Carbohydrates Starches, Cellulose, Gums and Pectins

Types of Complex Carbohydrates • Starches – most abundant complex carbohydrate in diet. • Composed of glucose • Main dietary source in U.S. is wheat flour • Nature’s reserve carbohydrate supply

Types of Complex Carbohydrates • Cellulose - known as fiber in the diet • Provides bulk in food – good for digestive functioning • Cannot be a food source for humans like it is for cows or termites since humans lack the digestive enzymes needed to digest • Forms rigid structure of plants – strings in celery and membranes surrounding kernels of corn are largely made up of cellulose.

Types of Complex Carbohydrates • Gums – available commercially for • Thickeners • Stabilizers • Trapping color and flavor • Example: gum arabic used in salad dressings and gummy candies

Types of Complex Carbohydrates • Pectins – occurs naturally in fruit; sugar acid that causes hydrogen bonding between negatively charged molecules resulting in thickened structure. • Key component in jams and jellies • Basic recipe for jams and jellies 1% pectin, 60-65% sugar, and 34-39%crushed fruit or fruit juice.

Functions of Complex Carbohydrates in Food Prep • Provide structure– the starch’s ability to thicken when heated and gel when cooled enables foods containing starch to take and hold many shapes.

Functions of Complex Carbohydrates in Food Prep • Bind – as a binding agent, complex carbohydrates tend to hold two other substances together • Amyloseor amylopectin molecules hold batters to vegetables and meats during deep-frying. If allowed to set 20 minutes before frying, binding is increased due to chemical reactions that take place.

Functions of Complex Carbohydrates in Food Prep • Thicken – starch can thicken liquids. This function is possible because of • Starch’s chemical structure • The size of its molecules • The way it reacts to heat

Gelatinization • Term used by food scientists to describe thickening a liquid with starch. • As the temperature increases, so does the swelling of the granule structure. • The temperature at which maximum swelling occurs is the gelatinization point. This is the point at which starch will hold the most water and the greatest thickening power.

Gelatinization • Applying heat to a starch-water mixture causes it to thicken (gelatinization). • As heat is added, starch opens up or stretches which allows water molecules to slip in the much larger starch molecules. • Heat increases the amount of water that can be trapped which will make the mixture become thicker.

Gelatinization • Salt and sugar caninterfere with thickening process by decreasing the strength and viscosity of the gel.

Physical Properties of Starch and Liquid Mixtures • Each starch has different physical properties • Food scientists must determine which type of starch is best for a given food product. • Five properties are evaluated: • Retrogradation • Viscosity • Stability • Opacity vs. translucency • Texture

Physical Properties of Starch and Liquid Mixtures • Starch and liquid combinations can be 4 types: • Slurries – uncooked mixtures of water and starch • Sols – thickened liquids – they are pourable. Examples: pancake, waffle and muffin batter. Cooked sols include white sauce and gravy.

Physical Properties of Starch and Liquid Mixtures • Pastes – thickened mixtures of starch and liquid that have very little flow, but thin enough to be spread easily. Example: the start of making a gravy • Gels – starch mixtures that are rigid. The stability is controlled by controlling the linear amylose starches and the branched amylopectins

Physical Properties of Starch and Liquid Mixtures • Retrogradation – the firming of a gel during cooling and standing. • Occurs because starch granules are trying to return to the structure they had before cooking. • Desirable when it causes a gel to thicken during cooling. • Undesirable if it continues to the point that cracks form in the gel. Ex. Gravy uncovered in refrigerator several days will develop these.

Physical Properties of Starch and Liquid Mixtures • Retrogradation (continued) • An important factor is serving temperature. • If serving a sauce immediately, then cook to desired thickness. • If served at room temperature, finish cooking while it is still thinner as it will thicken as it cools.

Physical Properties of Starch and Liquid Mixtures • Viscosity – is the resistance of a mixture to flow. • Food scientists run viscosity tests to measure how foods such as ketchup will flow.

Physical Properties of Starch and Liquid Mixtures • Stability – is the ability of a thickened mixture to remain constant over time and temperature changes. • Waxy maize starch – example of a stable starch when frozen or heated. It is a clear, soft paste that is as thick hot as cold. • Cornstarch – has more thickening power than flour; smoother in texture; makes appetizing mushroom gravy. But it does not reheat well

Physical Properties of Starch and Liquid Mixtures • Opacity vs. Translucency – refers to how much an object blocks light. • Cornstarch, potato starch, and arrowroot produce gels that are more translucent. Good to use in fruit sauces, fruit pie fillings, and glazes that are translucent. • Wheat flour is best used in chowders and white sauce.

Physical Properties of Starch and Liquid Mixtures • Texture – in this context has mostly to do with mouth feel. • Example: most people would not care for whole wheat flour being used to make a sauce or gravy because the texture would not be very smooth.

Thickening Sauces With Starch • Starch can be added to liquid to make a thickened sauce three basic ways. In each method, starch granules are separated to prevent lumping. • Cold water paste • Starch and fat • Starch and sugar

Thickening Sauces With Starch • Cold Water Paste – a method used to prevent lumps when thickening a sauce: • Quickly stir an equal amount of cold water and starch. • Continue stirring until a smooth paste is formed. • Then more liquid such as broth can be added to make a gravy.

Thickening Sauces With Starch • Starch and Fat – separate the starch granule with melted fat: • An equal amount of starch is added to heated fat. • Once starch is stirred into the fat, the liquid can be added SLOWLY, stirring constantly to keep the sauce smooth. • This method is used in making white sauce and gravy from meat drippings.

Thickening Sauces With Starch • Starch and Fat (continued) – Professional chefs often thicken soups and sauces using: • Buerre manie – is a ball of equal amounts of solid fat and starch mixed together. • These balls can be added to hot soups to thicken the broth. • The balls can be prepared ahead of time and refrigerated for several days or frozen for several months.

Thickening Sauces With Starch • Starch and Fat (continued) –Cajun cooks commonly use a roux to thicken sauces or gravy: • Rouxis a gravy that has had the starch heated in fat until it turns a rich red-brown. • Toasting the flour adds a distinctive flavor. • Needs low heat and constant stirring while browning the starch to prevent burning or uneven browning.

Thickening Sauces With Starch • Starch and Sugar – to avoid lumps with this method: • First thoroughly combine the starch and sugar. • Then gradually add the liquid with constant stirring. • Used most often in sweet sauces and puddings. • Presence of sugar also reduces the viscosity of the liquid and the resulting gel will be tender and smooth rather than rigid.

Nutritional Impact of Complex Carbohydrates • Starches divided into two categories: digestible starches and indigestible fiber. • Starches like sugar provide 4 calories/gram • Most abundant and economical source of calories available to people. • Carbohydrates should provide over 50% of your daily caloric intake. • Carbohydrates in the form of glucose is the only energy source your brain can use.

Nutritional Impact of Complex Carbohydrates • Excess carbohydrates are stored as glycogen. • The liver stores about 33% of total glycogen. • The muscles store the other 66.99% glycogen. • Fiber provides bulk – contributes to feeling full, aids digestion and elimination. • Fiber sources include whole grains, fruits and vegetables.

Nutritional Impact of Complex Carbohydrates • Nutritional Functions of Starches – in addition to providing energy, carbohydrates: • Provide bulk for digestive process • Tie up bile acids, decreasing their re-absorption • Lower cholesterol levels in the blood, retarding atherosclerosis • Promote the utilization of fat

Chapter 9 – The Complex Carbohydrates