microwaves + heat transfer + chemical changes

how does microwave cooking work

high-frequency electromagnetic waves cause water molecules in food to vibrate, producing heat

what affects microwave cooking time

oven wattage, weight of food, water content, volume of food

what is standing time in microwaving

time after cooking when food continues to cook as heat distributes

what materials are safe in a microwave

china, heat-resistant glass, paper, appropriate plastics

what materials are unsafe in microwaves

metal and foil

what is conduction

heat transfer by direct contact between molecules (e.g. pan to food)

exampes of conduction in cooking

shallow frying, stir frying, sautéing

why are wooden spoons used instead of metal

wood is a poor conductor of heat so it doesnt get hot quickly

what is convection

heat transfer by movement of liquids or gases; hot molecules rise, cool ones sink, creating currents

examples of convection in cooking

boiling water, baking in an oven, deep frying

what is radiation

heat transfer via rays from a hot source; travels in straight lines and heats the surface of food

examples of radiation in cooking

grilling, BBQ, toaster

what is dextrinisation

browning of starch when exposed to dry heat, forming dextrins and a sweeter flavour (e.g. toast)

what is caramelisation

browning of sugar when heated to high temperatures, forming a brown liquid (e.g. toffee, roasted veg)

what is the Maillard reaction

browning that occurs when protein and sugar/starch are present and exposed to dry heat (e.g. cake crust, browned meat)

what is enzymatic browning

browning of certain fruits/veg when cut and exposed to oxygen due to enzyme activity (e.g. apples)

what is denaturation of protein

permanent change in protein structure due ot heat, acid or mechanical action; proteins uncoil

what is coagulation of protein

setting of protein from liquid to solid when heated (e.g. fried egg, cooked meat)

what is gelatinisation

when starch is heated in liquid, granules swell and burst, absorbing liquid and thickening the mixture (e.g. white sauce, cooked rice)

factors affecting gelatinisation

amount of starch, type of starch, temperature (usually 75-87°C), too much sugar or acid can reduce thickening