Polyphenol Oxidase Activity And Antioxidant Changes Associated With Storage And Processing Of Four Food Crops.

ABSTRACT 

Four fresh food crops namely, Dioscorea rottindala (white yam), Xantliosonra spp. (cocoyam), 1pornoea batatas (sweet potato), and Solanurir tuherosum (Irish potato) were bruised, cut arid kept to deterorate. The stored samples were randomly selected daily and analyzed for polyphenol oxidase activity and the levels of antioxidants: p-carotene, vitamin C, vitamin E and glutathione for five days period. TIre fresh food crops were also subjected to various methods of heat processing namely, boiling, frying, and roasting and subsequently analyzed for antioxidant contents. Increased polyphenol oxidase activity and progressive loss of antioxidants from day 1 to day 5 in all the tubers were observed. Heat processing was also observed to result in loss of antioxidants in the fresh crops. It is suggested that (I) bruised and cut tubers should not be stored under ambient conditions to prevent considerable losses of antioxidants catalyzed by polyphenol oxidase and (ii) prolonged arid direct intense heat processing of tuber crops should be avoided, especially when peeled, to conserve their antioxidant contents.