ENZYME ACTION AND OFF‐FLAVOR IN FROZEN PEAS a

Enzymes are believed to be responsible for the development of off-flavor in raw and underblanched vegetables during frozen storage (1). A variety of enzymes have been suggested as being causative agents in flavor deterioration (l), but interest has centered mainly around catalase and peroxidase. Tests for the presence of these two enzymes have long been used as criteria of adequacy of blanching of vegetables prior to freezing. Furthermore, a reasonably good correlation has been observed between the presence of residual amounts of these enzymes and extent of off-flavor in frozen vegetables. To date, however, the identity of the responsible enzymes has remained obscure. Recently it has been shown that lipoxidase and lipase are responsible for the progressive deterioration of lipids in raw peas during frozen storage (5, 12). These changes in the lipids, characterized by increases in titratable acidity, development of lipid peroxides, and loss of chlorophyll, closely paralleled the progressive development of off-flavor (7). I t was deemed most likely that lipoxidase and possibly lipase are primary causative agents in the production of off-flavors during frozen storage of raw peas. Proof of involvement in off-flavor development of any or all of the above enzymes may be ascertained by a study of their action in model systems. Preparations of catalase, peroxidase, lipoxidase, and lipase of known specific activity were added to enzymatically inert blanched peas, and the samples analyzed after a suitable period of frozen storage. This paper reports the production of off-flavors during the frozen storage of macerates of blanched peas, brought about by the addition of enzymes, and a correlated chemical study of lipid deterioration.