The Effect of Processing on Ascorbic Acid and Dehydroascorbic Acid in Different Varieties of Yam

The effect of some processing method on the ascorbic acid and dehydroascorbic acid content of two cultivars of yam (Dioscorea rotundata and D. cayenensis) were investigated. The processing method adopted were cooking, frying and roasting. The assay of ascorbic acid in the two cultivars ranged from (5.0 – 9.2 mg / 100 g fresh tissue). The moisture contents of the processed samples ranged from 40-55% for D. rotundata and 48-60% for D.cayenensis except for roasted samples which had a moisture content of 30% for the two cultivars of yam. The pH values were similar in all the varieties examined. The level of ascorbic acid after 0 - 8 days of storage ranged from 5.2 - 7.3 mg / 100 g fresh tissue on a moisture -free basis (mfb). The dehydroascorbic acid content varied from 5.0 - 9.2 mg / 100 g fresh tissue on a moisture- free basis. The retention in ascorbic acid and dehydroascorbic acid of the various treatments ranged from 4.9 - 6.2 mg / 100 g and 5.2 - 8.9 mg / 100 g respectively. Thus, different processing methods has contributed to the loss of ascorbic acid with the highest loss observed when the yam samples were roasted and least loss when they were fried.