ABSTRACT
The challenge for the fresh food sector is to maintain quality at affordable prices. There are two modes of quality loss in fresh foods (Figure 12.1). Chemical deterioration occurs independently of enzymes (Chapters 9 and 10). Echoing the classical one-gene one-phenotype concept, biological deterioration can be described by a one-enzyme one-defect model (Chapter 11). Deterioration is due to multiple defect reactions each of which is catalyzed by a single enzyme. For instance, fruit softening is due to the enzyme ‘‘pectinase.’’ Discoloration is ascribed to polyphenol oxidase (PPO). Off-flavor is linked to products formed by lipoxygenase. This atomistic view is oversimplistic. The one-enzyme one-defect model arose from laboratory studies using single enzymes and substrates. Food deterioration due to aging and senescence is an extremely complicated phenomenon, which is only beginning to be unraveled using genetic tools.
