Plant foods, stabilized by heating (blanching) until all peroxidase activity is destroyed and then frozen, may be stored frozen for 1 to 2 years without significant deterioration of texture, color, flavor, or nutritional quality. Peroxidase is a convenient enzyme probe of adequate blanching. However, it is not the enzyme responsible for quality deterioration. Better quality products, with lower energy utilization, may be possible with less heat treatment by using the enzyme(s) responsible for quality deterioration as the detector for adequate blanching. To determine the enzyme(s) responsible for aroma and flavor deterioration, we identified the key aroma constituent(s) by sensory evaluation, isolated the enzyme(s) thought to be responsible, and added these enzymes, including peroxidase and catalase, back to blanched pureed vegetable singly and in all combinations. Following incubation, a trained sensory panel evaluated the aroma of the samples in relation to blanched and unblanched samples treated in the same manner. Lipoxygenase was identified as the key enzyme in English green peas and green beans, cystine lyase in cauliflower and broccoli, and probably lipoxygenase in corn‐on‐the‐cob. There may be another enzyme not yet identified involved.