The Effect of Environmental Variables on the Processing of Sweetpotatoes into Flakes and on Some Properties of Their Isolated Starches

SUMMARY Freshly harvested uncured sweetpotatoes were successfully processed into precooked dehydrated sweetpotato flakes by the controlled addition of amylolytic enzymes to the cooked puree prior to drying. The enzyme concentration required decreased as the harvesting sea‐son and storage period progressed. Reaction time was not critical when the enzyme concentration was not excessive. The puree was readily liquefied by commercial amylases, but the reducing sugar content of the flakes was not increased. To determine whether there might be a correlation between starch properties and the decreasing enzyme requirement, the effects of postharvest treatments of the sweetpotato were studied. The amylose content, pasting properties, and susceptibility to amylolysis of the isolated starch were determined. Curing with both optimum and prolonged storage effected changes in the pasting properties of the isolated starches. However, neither the susceptibilities of the starches to amylolysis nor their amylose contents were affected. Time of harvest and short‐term storage of the uncured roots did not alter any of the starch properties investigated. The processing characteristics of the sweetpotato could not be correlated directly to the properties of the isolated starches. It was observed, however, that although the starch fraction in the cooked puree was not saccharified by the amylolytic enzymes used in processing, β‐amylase was not inhibited in its action on the isolated starches.