Soybean protein isolate (SPI) was treated using ultrasound at 400 W for 5 and 15 min at 80 °C. The effects of ultrasound heat treatment on the structure of SPI and properties of glucono-δ-lactone induced SPI cold set gels (GSCG) were investigated. The results showed that ultrasound heat treatment of SPI reduced α-helixes and β-sheets and increased random coils, leading to a less compact tertiary conformation. The increase in surface hydrophobicity and free sulfhydryls changed the particle size of SPI and its gelation properties. However, the formation of GSCG mainly involved hydrophobic interactions rather than disulfide bonds due to the limitation of sulfhydryl group oxidation during acidification. Ultrasound heat treatment of SPI produced GSCG faster and increased the storage/elastic modulus (G′), gel strength and water holding capacity of GSCG, resulting in a more compact and homogeneous microstructure with smaller pores. The 5 min ultrasound heat treated GSCG had higher G′ and gel strength than 15 min, suggesting the synergistic effect of ultrasound and heat treatment. The results suggested that the combination of ultrasound and heat treatment might be an effective method for modifying the structure of SPI and improving the properties of GSCG.

大豆分离蛋白（SPI）在80 W下于400 W超声处理5和15分钟。研究了超声热处理对SPI结构和葡萄糖酸-δ-内酯诱导的SPI冷固化凝胶（GSCG）性能的影响。结果表明，SPI的超声热处理减少了α-螺旋和β-折叠层，增加了无规卷曲，从而导致了较低的三级构象。表面疏水性和游离巯基的增加改变了SPI的粒径及其胶凝性能。然而，由于在酸化过程中巯基氧化的限制，GSCG的形成主要涉及疏水相互作用而不是二硫键。SPI的超声热处理更快地产生了GSCG，并提高了GSCG的储能/弹性模量（G'），凝胶强度和持水量，导致具有更小孔的更致密，更均匀的微观结构。超声热处理5min的GSCG的G'和凝胶强度高于15min，提示超声与热处理的协同作用。结果表明，超声和热处理相结合可能是一种有效的方法来修改SPI的结构和改善GSCG的性能。