Kevin asked: “What, exactly, are enzymes?”
We do talk about enzymes a fair amount over here. But what are they all about?
Chemically, enzymes are proteins, and their specialty is helping other molecules to undergo chemical reactions. There are thousands of types of enzymes occurring naturally in plants, animals, microbes, and our bodies, and each one is specifically geared to facilitate a different reaction.
We care about enzymes because so much of cooking involves chemical reactions. Sometimes we want to encourage reactions, and sometimes we want to prevent them. Enzymes are the key.
Here are some of the enzymatic reactions we frequently come across in the kitchen.
A whole clove of garlic has a surprisingly subtle flavor, but the garlic we eat is seldom subtle. That’s because cutting, crushing, mashing, or chewing the clove allows chemical components that are stored separately to combine. A mild compound called alliin encounters an enzyme called alliinase, and instantly the enzyme starts to split the large alliin molecules into smaller molecules of allicin, which is extremely pungent. Over the ensuing minutes, allicin itself transforms into all of the different familiar potent garlicky flavor compounds.
In the kitchen, we sometimes try to prevent the reaction by cooking garlic whole or by treating it with acid, since high heat and low pH both minimize the activity of the enzyme. (Once garlic has been roasted, you can mash it as much as you want and it won’t develop any allicin pungency.)
A similar reaction happens when onions are cut: An enzyme called LF synthase combines with mild isoalliin and transforms it into lachrymatory factor (LF), the irritating compound that makes us tear up.