Microwave blanching: Effect on peroxidase activity, texture and quality of frozen vegetables

Carrot slices and French-Try style sweet potatoes were blanched for selected times (30-180 sec) in a microwave oven and a boiling water bath. Both blanched and unblanched samples were packaged and frozen-stored at -20 degrees C. Samples were evaluated for peroxidase inactivation and texture degradation before and after blanching and after storage for 3.5 and 7 months. Microwave and thermal kinetics of peroxidase inactivation and texture softening were comparable and followed semi-logarithmic models. Larger size samples of both carrots and sweet potatoes Indicated better inactivation of the enzyme, when heated in the microwave oven for mass-equivalent times. Although all frozen-stored samples, except those unblanched, were of acceptable quality at the end of the 7 month storage, samples blanched for Intermediate periods were generally superior. Microwave-blanched samples were comparable to Individually quick water-blanched samples, when the qualities of the frozen-stored samples were compared.