Some biochemical changes associated with post‐harvest storage of white yam (Dioscorea rotundata) tubers

Healthy Dioscorea rotundata tubers were kept for 8 months under local storage conditions and periodically analysed for the activity of some enzymes of carbohydrate metabolism as well as for the concentrations of key tuber metabolites. Except for polyphenol oxidase, all the other enzymes monitored showed low and maximum activities before and at onset of sprouting, respectively. The activities of these enzymes after sprouting remained higher than those in the pre‐sprouting period. Hexokinase, alcohol dehydrogenase and phosphorylase showed an approximately 2‐fold increase in activity at sprouting while glucose‐6‐phosphate dehydrogenase showed a more than 3‐fold increase in activity. Polyphenol oxidase (PPO) activity and starch content decreased steadily with storage with PPO activity decreasing to one‐half by the end of storage. L‐ascorbate, total polyphenols, carotenoids and lipids increased with storage and peaked at sprouting.