ABSTRACT
It goes without saying that proteins are very important in foods. Apart from their nutritional value they play an important role in texture of foods, they can act as emulsifiers, foaming agents, and gelling agents. Proteins are characterized by their primary (basically the amino acid sequence), secondary (a-helix and b-sheet), tertiary (3D structure), and quaternary structures (association of subunits). Processing can alter the secondary, primary, and quaternary structure, and this can have large consequences. Enzymes are, of course, also proteins. As shown in the previous chapter, enzymes can have a large
effect on food quality for the very reason that they act as catalysts. In the cases that such reactions are undesirable it is, obviously, important to prevent their action. Fortunately, enzymes can be inactivated relatively easily. Traditionally this is done by a heat treatment, but there are also other ways, such as high pressure, change in chemical environment (pH, solvent quality, ionic strength) change. In any case, knowledge of the kinetics of enzyme inactivation is essential, in order to be able to optimize the treatment. Since enzymes are proteins, the mechanism of inactivation is basically protein denaturation, and therefore it makes sense to discuss protein and enzyme denaturation in one chapter.
