MICROWAVE AND CONVENTIONAL BLANCHING EFFECTS ON CHEMICAL, SENSORY, AND COLOR CHARACTERISTICS OF FROZEN BROCCOLI

Broccoli (cv. Empress) obtained from a local supplier was blanched wit hin 15 h of harvest. It was blanched by four methods in covered contai ners: conventional boiling water (1900 mL, 4 min) (BW), steam (300 mL water, 4 min) (ST), microwave heated in 1 L glass containers (60 ml wa ter, 4 min, 700 W) (MW), and microwave heated in 1 L Seal-a-Meal(TM) b ags (45 ml water, 4 min) (MWB). Aliquots were frozen at -18C for 4 wee ks. Fresh unblanched broccoli peroxidase activity ranged from 389 to 8 29 units/min; activity was essentially zero immediately after all blan ching treatments. The highest reduced ascorbic acid (RAA) content occu rred in fresh unblanched broccoli. Some peroxidase regeneration occurr ed during frozen storage. Immediately after blanching, all blanched br occoli had lower RAA content than control broccoli. MW-blanched brocco li retained the greatest amount of RAA and had appearance, visual colo r, texture scores, and chroma of florets and stems equivalent to ST-bl anched broccoli. MW-blanched broccoli had flavor and general acceptabi lity scores similar to BW-blanched broccoli. After 4 weeks in frozen s torage, MW-blanched broccoli had the highest RAA content.