What chemical reaction is used in cooking that requires continual adding of energy?

Answer 1

There are many chemical reactions involved in normal cooking. Many of them are endothermic reactions that require constant addition of energy in order for them to continue to proceed. That is one reason why cooking involves heat. Another reason for heat addition in cooking is phase changes (like boiling water) which are not generally considered chemical reactions.

There are many oxidation reactions in cooking that require heat to proceed. Oxidation is combining other chemicals with oxygen. Burning is a common type of oxidation reaction.

When you make toast, you are drying and burning the bread. The color change is due mostly to oxidation reactions (the burning of organic compounds in bread). To keep toasting, you have to keep adding heat energy. Stop adding the energy and you stop toasting.

Answer 2

HEAT.