Abstract: The extraction efficiency, physicochemical properties, and structural characteristics of β-glucan extracted from highland barley branby sequential microwave-ultrasound-assisted extraction were explored. At the same heating rate, microwave enhanced α-amylase activity. The extraction efficiency of highland barley β-glucan was correlated with ultrasound power and treatment time. An ultrasound power of 600 W for 30 min and microwave heating at 60 ℃ for 30 min resulted in the maximum β-glucan yield of (6.30 ± 0.38)%. The results of physicochemical properties showed that with increasing sonication time up to 40 min, the solubility and foaming capacity of barley β-glucan increased significantly (P < 0.05), while the turbidity and emulsifying capacity decreased significantly (P < 0.05). The results of particle size distribution showed that with increasing sonication time, the relative molecular mass of barley β-glucan decreased, and ultrasound changed the rheological behavior of β-glucan, decreasingits viscosity and resulting in shear thinning. The infrared spectroscopic results showed that sonication did not change the functional groups of β-glucan, but it caused partial breakage of the glycosidic bonds. The microscopic results showed that ultrasonic treatment led to a looser structure of barley β-glucan, which was conducive to improving its extraction efficiency. Therefore, the microwave-ultrasound-assisted extraction of β-glucan from highland barley provides a basis for developing new food types and functional products.

Key words: combined microwave-ultrasound treatment; barley β-glucan; extraction efficiency; physicochemical properties; structural properties