Ultrasonic assisted extraction of mulberry leaf protein: Kinetic model, structural and functional properties, in vitro digestion

The world's protein resources are in short supply, and to develop a new source of plant protein, this experiment used ultrasonic-assisted technology to extract mulberry leaf proteins, and investigated the effects of different ultrasonic power densities (150, 300, and 450 W/L), ultrasonic temperatures (30, 40, and 50 °C), and ultrasonic time (2.5, 5, 7.5, 10, 12.5, 15, 17.5, and 20 min) on the yield and structure-function properties of mulberry leaf proteins. Peleg's model was used to describe extraction kinetics. The highest yield of mulberry leaf protein was 30.03 % at 50 °C, 450 W/L, and 20 min, which was 17.6 % higher than that of the control sample. The secondary and tertiary structures of mulberry leaf protein treated by ultrasound were changed, the content of α-helix and β-turn was decreased, the content of random coil and β-sheet was increased, the fluorescence intensity was changed, and the solubility, emulsification, antioxidant capacity, and in vitro digestibility were significantly improved. According to the experimental results, ultrasonic-assisted extraction technology can significantly increase the yield of mulberry leaf protein and effectively improve its structural and functional properties.