basic cooking principlesJudgment, Knowledge, Experience

effects of heat on foods

Foods are composed of proteins, fats, carbs, water, and vitamins and minerals.

They also consist of flavors and pigments (coloring agents).

Cooking affects all these components.

Cooking involves the chemical and physical reactions that affect the food.

carbohydrates

Starches and sugars are carbohydrates.

Found in fruits, vegetables, grains, beans, nuts.

heat affects on carbs1)

CARAMELIZATION : the browning of the sugars. Examples: browning of sauteed vegetables and the browning of bread crusts.

heat affects on carbs2) Gelatinization: The

absorption of water by starches causes the starch to swell. The chemical reaction used for thickening sauces and production of bread and pastries.

Acids inhibit gelatinization.

fruit and vegetable fibre

fruit & vegetable fiber

Fiber - provides structure and firmness to plants.

Fiber - cannot be digested.

Cooking fruits and vegetables breaks down the fiber.

Sugar makes fiber stronger. Sugar assists fruits in keeping their shape when cooked.

Alkalis, such as baking soda, makes fiber softer. They become mushy and lose flavor.

proteins

Protein is the major component of meats, poultry, fish, eggs, and milk.

proteins - coagulation

Proteins become DENATURED when the amino acids are heated and begin to break down.

proteins - coagulation

The strands then become attracted to one another and begin to BOND.

This bonding is called COAGULATION

coagulationThe solid network of these bonds becomes firm .

As the protein heats, it shrinks, becomes firmer and loses moisture.

Coagulation, (cooking), is usually completed at 160 - 185 degrees F.

maillard reactionMeat protein contains a small amount of carbohydrates.

When heated above 310° F the amino acids react with the carbohydrate molecules in a chemical reaction.

This occurs when meats brown and is called the MAILLARD REACTION.

This is done by searing the meat on a very hot dry surface.

connective tissue in meat

connective tissueProteins present in meats.

Meats with a lot of connective tissue are tough.

Some connective tissue dissolves during cooking.

ACIDS - speed coagulation AND help dissolve connective tissue.

fats

1. Fats are present in small quantities in most foods, they are present in larger quantities in: meats, poultry, fish eggs, and milk products.

2. Fats are important in cooking methods such as; frying.

3. Can be either solid or liquid at room temperature. Liquid fats are oils. Solid fats melt to become oils and change from solid to liquid. The melting point of fats varies.

smoke point

Fats begin to break down when heated.

When hot enough, they deteriorate and begin to smoke.

This is called the SMOKE POINT. It varies among fats.

A STABLE FAT has a high smoke point. It can be heated to a higher temperature, which is important when deep frying.

oil smoke points

oils &flavorings

Many flavors dissolve in fat & oil.

Fats are important carriers of flavor.

Flavors and vitamins can be lost when fats melt.

minerals, vitamins, pigments, flavors

1. Vitamins and minerals are important for nutrition.

2. Pigments and flavor are important for appearance.

3. Some are soluble in water and others are soluble in oil. It is important not to destroy these when cooking.

4. It is important to use cooking methods that preserve a food’s nutrients, taste, & appearance.

WATERI. Nearly all foods contain water.II.Dried foods contain as little as a fraction of 1% water.III. Fresh meat, fish, vegetables, and fruits consist mostly of water.IV.Three states of water: SOLID, LIQUID, GASV. LIQUID freezes at 0° C.VI. BOILS at 100° C and turns to steam.

VII. Water can also turn to gas at very low temperatures: EVAPORATION.VIII. Evaporation is responsible for the drying of foods.IX. This drying of foods allows them to be browned.X.When water carries compounds such as sugar or salt, the boiling and freezing points vary.

water

heat transfer

In order for food to be cooked; HEAT MUST BE TRANSFERED BY A HEAT SOURCE TO AND THROUGH THE FOOD.

The ways heat are transfered and the speed they are transfered at affect the cooking outcome.

conduction, convection, radiation or a combination.

conduction

1. Heat moves directly from one item to something touching it.

2. Heat moves from one part of something to other parts of the same item - through the food, from the exterior to the interior.

3. Heat moves rapidly through copper and aluminum, slower through stainless steel, slower through glass & porcelain.

CONDUCTION

convection

Heat is spread by movement of air, liquid or steam.

Natural - Hot liquids & gases rise while cooler ones sink. Natural circulation distributes heat.

Mechanical convectionMechanical Heat Transfer - Fans speed the transfer of heat - the food cooks faster.

Stirring is a form of mechanical convection.

Rate of Convection differs with thickness of liquid.

Once the heat is carried to the food; it is then distributed by conduction.

radiation

Energy is transfered by waves from a source to the food.

Waves are changed to heat energy when they hit the food.

Radiation in the Kitchen - INFRARED & MICROWAVE.

microwaveThe water molecules are agitated by the radiation energy, which creates heat and thus cooks the food.

Waterless materials will not heat.

Microwaves can only penetrate 2 inches into foods.

Larger foods are heated by conduction.

infrared

Broiling - most common

An electric or ceramic element heated by gas or electric, becomes so hot that it gives off infrared radiation.

High intensity infrared ovens designed to heat food rapidly.