Abstract: The effects of adding dried Lyophyllum decastes (DLR) or dried L. decastes by-products (DBY) on physicochemical properties and nutritional functions of extruded barley flour (BF) were analyzed. Results revealed a notable decrease in the degree of starch gelatinization in the DLR and DBY groups compared to the control group with nothing added. Gastrointestinal digestion simulation using the INFOGEST 2.0 method indicated that the antioxidant capacity of DBY was significantly higher than the BF group and DLR group (P < 0.05) due to its rich soluble dietary fiber content derived from L. decastes by-product. All the BF, DLR and DBY groups showed increased acetic acid production between 0 and 24 h of simulated colonic fermentation, thus leading to a significant reduction in pH (P < 0.05). Butyric acid levels significantly rose in all groups from 24 to 48 h. The DBY group displayed higher levels of acetic, butyric and propanoic acid compared to the DLR group at 72 h. Analysis of the gut microbiota highlighted the significant influence of individual variability on the regulatory effects of DLR and DBY, both of which notably promoted the growth of Dorea and Anaerostipes. Correlation analysis suggested that DBY augmented the levels of acetic and propanoic acid by stimulating Bifidobacterium (r > 0.5, P < 0.05). In summary, the incorporation of L. decastes or its by-products effectively enhanced the quality and functional attributes of barley flour products. Notably, DBY exhibited superior antioxidant activity and modulation of the gut microbiota. These findings offer theoretical support for the development of extruded L. decastes-barley products.

Key words: extrusion; barley; Lyophyllum decastes; in vitro digestion; fermentation; gut microbiota