Understanding the nutritional, structural, and physicochemical properties and in vitro digestibility of thermally-treated whole grain highland barley

Abstract

Abstract This study focused on the effect of thermal processing including atmospheric boiling (AB), high-pressure boiling (HPB), and baking (B) on the nutritional and structural properties, gelatinization properties, and in vitro digestibility of starch and protein of whole grain highland barley (HB). Various thermal processing affected the nutritional profile and pasting properties of HB at different extent due to the function of heat-moisture or dry heat. Starch gelatinization of AB-HB and HPB-HB was promoted compared to untreated native HB, whereas, B-HB delayed starch gelatinization. Thermal processing reduced the relative crystallinity of HB compared to untreated native HB. Processing of AB and HPB increased the content of rapidly digestible starch (RDS) and decreased the contents of slowly digestible starch (SDS) and resistant starch (RS) compared to native HB. There was no significant difference of contents of RDS, SDS, and RS between B-HB and untreated native HB. Estimated glycemic index (eGI) of AB-HB and HPB-HB was significantly increased compared to native HB, whereas, eGI of B-HB was significantly reduced. Protein digestibility of native and B-HB was significantly lower than that of AB-HB and HPB-HB during gastric digestion. In the intestinal digestion, protein digestibility of HPB-HB was the highest, then followed by AP-HB, native HB, and B-HB. Digestion and thermal processing both influenced molecular weight of protein subunits of HB. Overall, this research provided theoretical foundation for the effect of thermal processing on whole grain HB regarding to the nutritional profile, physiochemical properties, and in vitro digestibility of starch and protein.