Subtle differences in starch fine molecular structure are associated with large differences in texture and digestibility of Chinese steamed bread

Abstract

Chinese steamed bread (CSB) is a staple food for a large number of people in China, but it has a high glycemic index, which is nutritionally undesirable. Developing a CSB with more slowly digestible starch has been achieved, but current processes for this result in a product with poor sensory appeal. In this study, the relations among starch chain-length distribution, starch digestibility and texture of CSBs made from 10 different wheat flour varieties were investigated, the long-term aim being to develop CSBs with an optimal combination of slow starch digestibility and desirable texture. Although there were only small differences among the CLDs of different wheat flours, they were strongly correlated to the differences of both starch digestibility and textural attributes of CSB. A slower starch digestion rate was associated with relatively longer amylose intermediate to long chains, lower amounts of amylopectin short chains and higher amounts of amylose short chains. A softer CSB texture was related to a relatively higher amount of amylopectin long chains and shorter amylopectin short chains. A higher springiness/resilience of CSB was associated with more amylopectin long chains, longer amylose intermediate to long chains, fewer amylose long chains, and smaller average chain length of amylopectin short chains. A higher cohesiveness of CSB was developed with a higher amount of amylopectin long chains. These results suggest that it is feasible to produce CSB with both slow starch digestibility and desirable texture, by choosing the wheat flour with optimized starch structures. Small variance of wheat starch chain-length distribution can cause a significant difference of starch digestibility and texture of Chinese steamed bread. • Small differences exist among wheat starch chain-length distributions. • Slower starch digestibility associated with higher amounts of amylose short chains. • A softer texture of Chinese steamed bread related to more amylopectin long chains. • Higher springiness of Chinese steamed bread related to fewer amylose long chains.