Nanofibrils, an effective method to modulate the functional properties of proteins, can be promoted by ultrasound pretreatment. This study investigated the effect of ultrasound pretreatment on the structure, functional property, antioxidant activity and digestibility of soy protein isolate (SPI) nanofibrils. The results showed that high amplitude ultrasound had a significant effect on structure of SPI nanofibrils. SPI nanofibrils pretreated by 80% amplitude ultrasound showed a blueshift of the amide II band in Fourier transform infrared spectroscopy (FTIR), resulted in more tryptophan residues being buried and increased the crystallinity. Low amplitude ultrasound (20%) pretreatment significantly improved the solubility, emulsifying activity index (EAI) and water absorption capacity (WAC) of SPI nanofibrils, but 80% amplitude ultrasound pretreatment of SPI nanofibrils reduced emulsifying stability index (ESI). High amplitude ultrasound (60% and 80%) pretreatment of SPI nanofibrils improved the foaming capacity and foaming stability and decreased denaturation temperature. DPPH radical scavenging activity of SPI nanofibrils were significantly improved by ultrasound pretreatment. 20% amplitude ultrasound pretreatment improved DPPH, ABTS radical scavenging activity and ferric reducing antioxidant power of SPI nanofibrils. The digestion rate of 80% amplitude ultrasound-pretreated nanofibrils were consistently higher, and SPI nanofibrils pretreated by ultrasound were more fragmented and shorter after simulating gastrointestinal digestion. This study would expand the application of food-grade protein nanofibrils in the food industry.

纳米原纤维是一种调节蛋白质功能特性的有效方法，可通过超声预处理得到促进。本研究调查了超声预处理对大豆分离蛋白 (SPI) 纳米原纤维的结构、功能特性、抗氧化活性和消化率的影响。结果表明，高振幅超声对SPI纳米纤维的结构有显着影响。经 80% 振幅超声预处理的 SPI 纳米原纤维在傅里叶变换红外光谱 (FTIR) 中显示出酰胺 II 波段的蓝移，导致更多的色氨酸残基被掩埋并增加了结晶度。低振幅超声（20%）预处理显着提高了SPI纳米纤维的溶解度、乳化活性指数（EAI）和吸水能力（WAC），但 SPI 纳米纤维的 80% 振幅超声预处理降低了乳化稳定性指数 (ESI)。SPI 纳米纤维的高振幅超声（60% 和 80%）预处理提高了发泡能力和发泡稳定性并降低了变性温度。超声预处理显着提高了SPI纳米纤维的DPPH自由基清除活性。20% 振幅超声预处理提高了 SPI 纳米纤维的 DPPH、ABTS 自由基清除活性和铁还原抗氧化能力。80%振幅超声预处理的纳米纤维的消化率一直较高，模拟胃肠消化后，超声预处理的SPI纳米纤维更碎裂、更短。这项研究将扩大食品级蛋白质纳米纤维在食品工业中的应用。