Abstract: This study evaluated the effect of heat-moisture treatment (HMT) on the basic nutritional composition, digestive properties, metabolite profile, and in vitro promoting effect on probiotic proliferation of whole-grain highland barley (Hordeum vulgare L.). The results showed that the β-glucan, amylose, and resistant starch contents of HMT-treated highland barley (HMT-HB) were significantly increased by 8.01% (P < 0.05), 73.04% (P < 0.05), and 51.06% (P < 0.05) compared with native highland barley (HB), respectively. In addition, HMT-HB demonstrated significantly elevated levels of lipids and lipid-like molecules, organic acids and their derivatives, and organic oxygen compounds as well as significantly reduced levels of organonitrogen compounds, alkaloids and their derivatives, nucleosides, nucleotides, and their analogues. Based on the identification of differential metabolites, the metabolic pathways of HMT-HB were found to be primarily enriched in purine metabolism, aminoacyl-tRNA biosynthesis, and linoleic acid metabolism. Further evaluations revealed that highland barley flour, both before and after HMT, significantly promoted the proliferation of Limosilactobacillus reuteri, Lactobacillus acidophilus, and Enterococcus faecalis (P < 0.05), whether utilized as an alternative carbon source or a supplementary carbon source. Notably, HMT-HB was more effective in this regard. The above findings provide a theoretical basis for the development of whole-grain highland barley-based health foods.

Key words: highland barley; heat-moisture treatment; probiotics; metabolites; digestive characteristics