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ABSTRACT

Green beans were blanched by four methods: water blanching, steam blanching, microwave blanching and convection oven blanching. Minimum adequate blanch time for complete peroxidase enzyme inactivation was less in the microwave oven. Weight loss was significant in the samples blanched in the convection oven due to moisture vaporization. Ascorbic acid was found to be significantly (P < 0.05) higher in the microwave blanched sample. The ascorbic acid contents of water blanched green beans were higher than those of steam blanched ones. Convection oven blanched green beans were found to be lowest in ascorbic acid and chlorophyll contents, and microwave treated samples were found to be highest. For equivalent peroxidase inactivation, more losses of chlorophyll were detected in steam blanched samples than in water blanched samples. The results of color measurements with a Hunterlab colormeter indicated that blanching with water and steam resulted in a more intense greenness of the samples.