Residual peroxidase activity as influenced by blanching, SO 2 treatment and freezing of cauliflowers

The influence of blanching time and SO 2 treatment on the residual peroxidase activity and its implication for the sensory quality of frozen cauliflowers were assessed after storage for up to one year at −18°C. The treated cauliflowers, sealed in polythene bags, were placed in waxed paperboard cartons and frozen in a contact plate freezer at −35°C. The sensory quality of frozen stored cauliflowers related well to their residual peroxidase activity, which was sensitive to the SO 2 treatment. Blanched cauliflowers following a brief dip in a metabisulphite solution prior to freezing gave a significantly (P<0.05) superior product even when stored for one year. The residual peroxidase activity, which ranged from 1 to 5.5% in the blanched samples, was below 1 % in the SO 2 ‐treated samples, and the SO 2 content of50 ppm found in these stored samples disappeared after 3 min cooking in boiling water.