Biochemical changes during storage of sweet potato roots differing in dry matter content

Changes during storage were investigated in carbohydrate level, digestibility, alpha-amylase, trypsin inhibitor activity and pasting properties of roots of six genotypes of sweet potato (Ipomoea batatas (L.) Lam) differing in dry matter content. Most genotypes showed a slight decrease in starch content during 0-180 days of storage, but in the genotype Hi-dry, it decreased substantially. Alpha-amylase activity increased during the first 2 months of storage, followed by a decrease with continued storage to a level similar to that at harvest. The decline in starch content was correlated with alpha-amylase activity in the first 60 days storage (r = 0.80, P = 0.06). Trypsin inhibitor activity (TIA) in the fresh roots varied among genotypes from 3.90 to 21.83 U/mg. Storage had little influence on TIA level. There was considerable genotypic variation in digestibility, with up to 27% reduction in digestibility after 120 days in storage. Glucose and sucrose concentration increased early in storage and then remained fairly constant. Storage reduced flour pasting viscosities, with up to nearly a 30% decline in peak viscosity. (C) 2002 Elsevier Science B.V. All rights reserved.