Structural characteristics of β-glucans from various sources and their influences on the short- and long-term starch retrogradation in wheat flour

Abstract

Beta-glucans possess the ability of retarding starch retrogradation. However, β-glucans from different sources might show various influences on retrogradation process and the structure-function relationships of β-glucans related to the feature still remains unclear. In the study, the β-glucans from oat (OG), highland barley (HBG), and yeast (YG) were selected. Each β-glucans formed aggregate as observed by atomic force microscopy. OG and HBG with a lower M_w aggregated more obviously and exhibited higher intrinsic and apparent viscosity. The two β-glucans showed more restraining effect on the short-term starch retrogradation in the sol-like test system (RVA) and the long-term starch retrogradation in the gel-like test system (DSC). However, YG with a higher M_w exerted a greater retarding effect on the short-term starch retrogradation in gel-like test systems (Mixolab and rheology). LF-NMR indicated that OG and HBG increased the population of less-bound water by wrapping around the starch. In summary, the structural characteristics of β-glucan (M_w and aggregation state) and experiment condition (solid content) jointly influenced starch retrogradation, because a lower Mw and higher aggregation capacity β-glucan interacted more readily with starch and inhibited more starch re-association due to the higher diffusion rate in the sol-like system.

Keywords: Conformation; Retrogradation; Structure-function relationship; Wheat flour; β-Glucan.