Postharvest Storage Affects Sweetpotato Water-soluble Vitamin Composition

Water soluble vitamins (WSV), including vitamin C and the B vitamins, are important nutritional quality components in fruits and vegetables. The WSV content has been found to be influenced by different postharvest conditions and storage durations in various fruits and vegetables. In sweetpotato, however, limited information exists on the influence of storage on water soluble vitamin content. The objective of this study was to determine the effect of curing (31 °C and 90% relative humidity for 7 days) and storage (14 °C for 3 and 6 months) on vitamin C, thiamine (vitamin B1), riboflavin (vitamin B2), and vitamin B6 content in four sweetpotato cultivars. Vitamin C (measured as total ascorbic acid) remained similar during curing in three cultivars (Beauregard, Covington, and Orleans), but decreased in LA 07-146. Storage for 3 months did not affect ascorbic acid content in three cultivars, but it declined in Covington. All cultivars, except Orleans, decreased in ascorbic acid content after 6 months of storage. Thiamine content did not change during curing in three cultivars, but decreased in Covington. Thiamine content generally did not decrease during 6 months of storage. Although riboflavin showed a reduction of one-third in all cultivars during curing, it remained stable during 6 months of storage. Vitamin B6 content did not change during curing or 3 months of storage. The overall results indicated that long-term storage for 6 months of most sweetpotato cultivars generally resulted in a loss in ascorbic acid content, but little or no loss in riboflavin, thiamine and vitamin B6.