Color Deterioration in Frozen French Beans (Phaseolus vulgaris). 2. The Effect of Blanching

SUMMARY The effect of blanching on the conversion of chlorophylls to pheophytins and on their oxidation during the blanching and subsequent storage of green beans at ‐10° C was examined. Some conversion of chlorophylls to pheophytins occurred during blanching but there was no oxidation. During storage at ‐10 °C, both conversion and oxidation occurred. Two effects of blanching were distinguished: firstly, as enzymes were inactivated, the rates at which the chlorophylls underwent changes in storage at ‐10°C diminished; secondly, with blanch periods longer than necessary for inactivation of peroxidase and catalase the rates of chlorophyll change increased progressively during frozen storage. Under the blanching conditions used, a blanching period of 45 see to 1 min resulted in the most stable product.