Assessment of Microwave Blanching as a Preparatory Tool for Home Freezing of Yellow Squash ( Cucurbita pepo ) J. ROBERT

1. Assessment of Microwave Blanching as a Preparatory Tool for Home Freezing of Yellow Squash (Cucurbita pepo) J. ROBERTS, L. T. Walker and J.C. Anderson Department of Food & Animal Sciences Alabama A & M University, P.O. Box 1628, Normal, AL 35762 ABSTRACT Microwave blanching of fruits and vegetables has been identified as a process that retains nutrients better than conventional blanching methods (boiling water and steam). Only low energy level (500-700 Watt) microwaves using selected vegetables have been investigated in the past. Further studies are necessary to determine the effect of today’s higher energy level microwaves on the blanching of vegetables. Yellow squash was blanched in covered containers for 3 min using: boiling water (BW), steam (ST), and 3 microwaves (1000 watt - MW1, 1200 watt - MW2, and 1300 watt - MW3). Samples were ice-cooled, placed in freezer bags, and stored at –18oC for 6 months. Enzyme activity, physico/chemical, nutritional and sensory parameters were assessed during and following 6 months of frozen storage. Peroxidase (POD) activity decreased from 2.77-4.03 units (unblanched - UB) to 0.005-0.138 units after initial blanching. The MW3 treatment retained 96% Fe (170 mg/kg) and 93% K (2133 mg/kg), which was significantly higher than the other microwave blanch treatments. Total ascorbic acid (TAA) retention was highest (14.4 mg/100g) for the ST blanched treatment (97%). There were no significant TAA retention differences among the MW3 and ST treatments. Texture values were least firm for the BW treatment (66 Newtons) due to an increased cooking effect. Sensory preference scores indicated a level of acceptance that was no different from the commercial (control) product. The study indicated that the overall quality of MW (all 3 energy levels) blanched yellow squash was as good as or superior to BW and ST blanching methods. The availability of this and other such information to home preservers of fruits and vegetables could lead to a higher quality of products for consumption. 200 180 0.16 Initial 160 4 mo 0.14 140 Initial 6 mo 4 mo 120 Shear Force (Newtons/15g ) 0.12 6 mo 100 80 0.1 Enzyme Activity (units POD/mL filtrate) 60 0.08 40 20 0.06 0 UB MW1 MW2 MW3 BW ST 0.04 Treatments 0.02 0 MW1 MW2 MW3 BW ST Treatments 16 14 12 10 TAA (mg/100g) 8 6 4 2 0 UB MW1 MW2 MW3 BW ST Treatments This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.