Structural characteristics and functional properties of walnut glutelin as hydrolyzed: effect of enzymatic modification

Currently, edible walnuts are either eaten fresh or being processed as walnut oil. However, the walnut dregs produced after the oil is pressed from the walnuts cannot be used for comprehensive utilization. Instead, they are often used as animal feed after simple treatment or directly used as waste landfill. The walnut dregs contain >20% of high-quality plant protein. Walnut protein consists of gluten, prolamin, albumin, and globulin. Poor function of walnut protein has been reported. Therefore, the gluten in walnut cake protein was modified by enzymatic method and the microstructure of walnut protein was changed, thereby improving the functional properties of walnut protein. It is generally believed that walnut protein modified by enzymatic method might be more suitable for industrial production. Our study showed that the modified walnut glutelin (WG) increased the solubility by ~1.33 times, the water holding capacity by ~0.23 times, the emulsifiability by ~0.32 times, and the emulsion stability by ~0.75 times. The oiliness was slightly lowered and the foaming characteristics were not greatly changed. Therefore, our study concluded that the microscopic structure of the protein had undergone certain changes based on the spectrum and electron microscopy. The modification of the microstructure also provides a theoretical basis for the comprehensive utilization of walnut protein, which could broaden the application of walnut protein in the industrial food production.