Effect of different treatments on nutrient composition and In vitro fermentation characteristics of highland barley

This study investigated how processing methods modify highland barley (HB) flour's properties. HB flour was treated with: extrusion (EHB), high-pressure (HHB), microwave (MHB), superfine grinding (SHB), and glutamine transaminase (THB). Nutritional composition was analyzed using standard methods. Results showed that, TGase treatment significantly increased protein content by 6.17 g/100 g ( p < 0.05). Extrusion significantly increased total dietary fiber, β-glucan content by 4.75 g/100 g, 3.06 g/100 g ( p < 0.05). Using the processed HB flours as the sole carbon source, in vitro fermentation was conducted with human fecal microbiota. Results showed that all treatments significantly altered the overall composition of the gut microbiota in a model simulating the human distal colon, compared to untreated HB. EHB fermentation specifically and significantly reduced the abundance of Proteobacteria while increasing Bifidobacterium abundance ( p < 0.05). SHB fermentation significantly increased Lactobacillus abundance ( p < 0.05). Metabolome analysis indicated that all modified HB flours enhanced lipid, glucose, and amino acid metabolism. Furthermore, Pearson correlation analysis revealed a strong positive correlation between Bifidobacterium abundance and soluble dietary fiber/β-glucan content, and between Bacteroides abundance and γ-aminobutyric acid content. These findings indicate that processing methods differentially enhance HB's nutritional value and microbiota-modulating potential, with EHB, SHB and THB showing particular promise for functional food applications. • TGase treatment increased protein content by 40.6 %. • Extrusion boosted total dietary fiber (24 %), resistant starch (62.1 %), and β-glucan (36.8 %). • Extrusion reduced proteobacteria while increasing bifidobacteria. • Superfine grinding significantly raised lactobacillus abundance. • Correlated with soluble dietary fibers and β-glucan. bacteroides strongly linked to γ-aminobutyric acid.