Impact of sweetpotato starch structures, thermal properties, and granules sizes on sweetpotato fry textures

Abstract

Sweetpotato French fry (SPFF) textures have been previously correlated with starch contents, but little is known about the relationship of starch properties with SPFF textures. Associations of SPFF textures with starch properties were explored by comparing starch thermal properties (gelatinization temperatures and starch type percentages), amylopectin chain length distributions, and granules sizes among genotypes that produced a wide range of SPFF textures. SPFF textures were modeled with these starch data and raw sweetpotato compositions to investigate the impact of starch attributes on SPFF textures. Starch structures, thermal properties, and granule sizes varied among genotypes. In general, starches from orange-fleshed sweetpotatoes had lower degrees of polymerization (DP) (more DP 6–9 chains and fewer DP 18–25 chains), more B-type starch, and lower gelatinization temperatures than yellow or cream-fleshed genotypes, but no differences in granule size distributions. Predictions of fry textures using raw composition were significantly improved when starch properties were included. Starch thermal properties, particularly the percentage of A-type starch, most influenced the prediction of SPFF textures. Structural equation modeling identified causal relationships between SPFF textures and starch properties. Starch thermal properties and the interaction with α-amylase levels had the strongest correlations with SPFF textures. Alongside raw compositions, starch thermal properties provide valuable information for predicting SPFF textures that could be used to make varietal selections by processors and breeders.