Effects of ultrasonic pretreatment of soybean protein isolate on the binding efficiency, structural changes, and bioavailability of a protein-luteolin nanodelivery system

The combination of protein and flavonoids can ameliorate the problems of poor solubility and stability of flavonoids in utilization. In this study, soybean protein isolate pretreated by ultrasonication was selected as the embedding wall material, which was combined with luteolin to form a soybean protein isolate-luteolin nano-delivery system. The complexation effect and structural changes of soybean protein isolate (SPI) and ultrasonic pretreatment (100 W, 200 W, 300 W, 400 W and 500 W) of soybean protein isolate with luteolin (LUT) were compared, as well as the changes in digestion characteristics and antioxidant activity in vitro. The results showed that proper ultrasonic pretreatment increased the encapsulation efficacy, loading amount and solubility to 89.72%, 2.51 mu g/mg and 90.56%. Appropriate ultrasonic pretreatment could make the particle size and the absolute value of zeta-potential of SPI-LUT nanodelivery system decrease and increase respectively. The FTIR and fluorescence results show that appropriate ultrasonic pretreatment could reduce alpha-helix, beta-sheet and random coil, increase beta-turn, and enhance fluorescence quenching. The thermodynamic evaluation results indicate that the Delta G < 0, Delta H > 0 and Delta S > 0, so the interaction of LUT with the protein was spontaneous and mostly governed by hydrophobic interactions. The XRD results show that the LUT was amorphous and completely wrapped by SPI. The DSC results showed that ultrasonic pretreatment could improve the thermal stability of SPI-LUT nano-delivery system to 112.66 +/- 1.69 degrees C. Digestion and antioxidant analysis showed that appropriate ultrasonic pretreatment increased the LUT release rate and DPPH clearance rate of SPI-LUT nanodelivery system to 89.40 % and 55.63 % respectively. This study is a preliminary source for the construction of an SPI nanodelivery system with ultrasound pretreatment and the deep processing and utilization of fat-soluble active substances.

Automated summary

This study investigated the use of ultrasound pretreatment to improve the encapsulation efficacy, solubility, and stability of a soybean protein isolate-luteolin nano-delivery system. The results demonstrated that ultrasound pretreatment enhanced the performance of the system, including increased loading amount and solubility, decreased particle size, and improved thermal stability. It also showed that ultrasound pretreatment increased the release rate and antioxidant activity of the nano-delivery system. This research provides preliminary evidence for the development of ultrasound pretreatment in the construction of protein-based nano-delivery systems.