Physical-assisted deep eutectic solvent improves the extraction of soluble dietary fiber from highland barley bran and its effects on structure, properties and functions.

Highland barley bran is a vastly underutilized by-product with limited efficient utilization techniques. This study established a green, low-carbon physical-assisted deep eutectic solvent (DES) method to extract soluble dietary fiber (SDF) from highland barley bran. The impacts of ultrasound, microwave and high-speed shearing assistance on the extraction yield, structure, chemical properties and in vitro biological activities of SDF were comprehensively evaluated. Response surface methodology was adopted to optimize DES and extraction parameters: extraction temperature 70 °C, extraction time 90 min, water content 48%, choline chloride-citric acid ratio 2:1, liquid-solid ratio 20:1 mL/g. The maximal SDF yield reached 12.08%, markedly exceeding 6.10% of conventional enzymatic extraction. Combined physical assistance further increased the average yield to 14.94%, with enhanced in vitro bioactivities. This study provides a theoretical basis for the high-value utilization of highland barley bran.