The contribution of cell wall integrity to gastric emptying and in vitro starch digestibility and fermentation performance of highland barley foods

Studies have shown that the structure, composition, and bioavailability of compounds in whole grains are affected by processing and the role of cells walls. In this study, the effects of different processing methods on highland barley, one of the mostly widely produced whole grains worldwide, were investigated. The processing methods applied were flaking-boiling (HB flake), sand-roasting (Puffed HB), and sand-roasting-milling (Tsamba). Results showed Puffed HB and Tsamba had higher levels of damaged starch content, starch short-range molecular order, and relative crystallinity than HB flake. The half-time of gastric emptying (t1/2) was the slowest for Tsamba (132.3 min) compared to HB flake (122.5 min) and Puffed HB (84.0 min), indicating the slowest gastric emptying rate, which could be attributed to its high viscosity of gastric digesta. After in vitro gastroduodenal digestion, Puffed HB exhibited the lowest starch digestibility and the least amount of β-glucan due to its less damaged cellular structure. Furthermore, Puffed HB resulted in a 21% and 18% higher in vitro production of total short-chain fatty acids than Tsamba and HB flake, respectively. Besides, undigested starch of Puffed HB after in vitro gastroduodenal digestion delayed in vitro fecal fermentation of β-glucan. Our study provided insight into the potential mechanisms of how cell wall integrity affected the gastric emptying, in vitro starch digestibility, and in vitro fecal fermentation of highland barley foods.