9. Enzymes are Inactivated.

Enzymes are proteins that act as biological catalysts in plants, animals, and microorganisms. They catalyze, or speed up, chemical reactions without actually being used up in the process. This makes enzymes very efficient, so that a small amount goes a long way. Not only can enzymes speed up chemical reactions; they can cause reactions to occur that might not happen otherwise.

All enzymes, being proteins, are denatured by heat. The process of denaturation inactivates enzymes and stops their activity. Most enzymes are inactivated by temperatures of 160°–180°F (70°–80°C), but they vary in their heat sensitivity. Before they are inactivated, however, rising oven temperatures increase their activity. This increased activity occurs in the early stages of baking only.