Effect of ultrasound pretreated drying on functional and nutritional attributes of soy protein isolate: A comparative study with freeze, spray and oven-drying methods.

This study examines effect of ultrasound pretreatments (5, 10, and 15 min at 350 W) and freeze-drying (FD), spray drying (SD), and oven drying (OD) on functional and nutritional properties of soybean protein isolate (SPI) powder. Results indicated that lysine was most heat-sensitive amino acid and it underwent a significant reduction in ultrasound-pretreated dried samples, with a decrease of up to 13.65 % compared to control samples. Across all drying conditions, SD is more effective in enhancing foaming stability (83.78 %-88.21 %) and reduced browning index (1.17-1.89) compared to other methods. In contrast, FD maintains a superior emulsification activity index and oil holding capacities ranging (9.83-19.21 m/g) and (2.49 %-7.16 %) than that of other drying techniques. Morphological analysis revealed that FD produced irregular porous structures, while SD and OD resulted in more compact and wrinkled structures. These findings provide valuable insights and serve as a reference for production and application of SPI.