Effects of Heat-Moisture Treatment and Pullulanase Treatment on the Nutritional Functionality, Biological Activity and Physicochemical Characteristics of Highland Barley Flour

To address the challenges of low nutrient utilization, insufficient biological activity (such as β-glucan), and poor processing adaptability associated with highland barley (Hordeum vulgare var. coeleste) flour and to enhance its application value in functional foods, this study employed wet-heat treatment and pullulanase treatment to modify highland barley flour. Changes in its physicochemical compositions, biological activity, enzyme inhibition capacity, digestibility, and particle structure before and after modification were examined, aiming to provide theoretical support for its further development. The findings revealed that both treatments significantly increased the content of key nutrients compared with the unmodified control group. Specifically, wet-heat treatment elevated the levels of dietary fiber and β-glucan from 10.50% and 5.60% to 12.81% and 6.76%, respectively. Pullulanase treatment enhanced these components to 11.46% and 9.11%, respectively, while also significantly increasing protein and essential amino acid levels. Notably, isoleucine (Ile), leucine (Leu), and tryptophan (Trp) levels were 1.5, 1.8, and 1.6 times higher in the pullulanase treatment group than in the control group, respectively. Furthermore, the total phenolic, flavonoid, and anthocyanin contents, along with the scavenging capacity against 2,2'-azobis (3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) cation radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and ferric reducing antioxidant power (FRAP) were significantly increased by both treatments, with pullulanase treatment being more effective. Moreover, they significantly increased the inhibitory activities of barley flour against α-glucosidase and α-amylase, with pullulanase treatment having a more pronounced effect. In vitro digestion experiments indicated that barley flour had a medium glycemic index (GI) of 56.13. However, after wet-heat and pullulanase treatments, its estimated glycemic indices significantly decreased to 54.61 and 51.88, respectively, aligning with the criteria for low GI foods. In terms of physicochemical properties, the peak gelatinization temperature of barley flour increased from 59.18 to 65.49 and 59.68 ℃, respectively, and the gelatinization enthalpy rose from 4.99 to 5.55 and 6.88 J/g, respectively. Additionally, the particle size distribution became more concentrated, with D₅₀ decreasing from 205.01 μm to 135.20 μm and 25.04 μm after wet-heat and pullulanase treatments, respectively. Under scanning electron microscopy (SEM), both treated samples exhibited surface dents and cracks, with more pronounced structural damage observed in the pullulanase-treated group. Overall, wet-heat treatment was more effective in enhancing the gelatinization stability and dietary fiber content of barley flour, while pullulanase treatment offered distinct advantages in enriching β-glucan content, essential amino acid levels, biological activity, and enzyme inhibition capacity. In conclusion, both modification processes enhance the nutritional functionality and processing characteristics of barley flour, allowing for the selection of an appropriate modification strategy based on the specific requirements of target functional foods.