Influence of cell-wall permeability on starch digestion in sweet potato cells

Abstract

This study aims to evaluate the effects of cell-wall permeability on starch digestibility in sweet potato (SP) cells. Intact cells were separated from purple, red, and white SP tubers, which differ in terms of cell-wall composition and structure, and used as whole SP food models. Purple SP cells exhibited markedly higher polyphenol content but lower starch crystallinity than red and white SP cells. Thermal analysis showed that the gelatinization enthalpy of starch considerably increased due to cell wall damage and the damaged cells of purple SP increased more. The purple SP cell wall dissolved the least pectin and had the lowest permeability for amylase-sized fluorescence probes after cooking, indicating it had stronger thermal stability and resistance to amylase penetration. Among the three cell samples, purple SP cells had the highest starch digestibility (93.95%) when the cell walls were damaged; however, when cell walls remained intact, the starch digestibility (75.95%) of purple SP cells was significantly lower. Therefore, cell-wall permeability mainly controls starch digestion within SP tubers. More polyphenols may enhance cell-wall stability and barrier amylase capacity. This study provides novel insights into the function of the cell wall, which protects starchy plants from the action of amylase.