Effect of enzymatic hydrolysis conditions on structure of soy protein isolate/gum arabic complex and stability of oil‐in‐water emulsion

The emulsifying, antioxidant and foaming properties of soy protein isolate hydrolysates (SPH) can be improved by the addition of gum arabic (GA). We investigated the effects of different hydrolysis conditions on the complexation of SPH and GA, and the effects of the complex on the properties of emulsions.Fluorescence spectroscopy showed that the addition of GA had a stronger effect on bromelain and pepsin hydrolysates than trypsin hydrolysate, and therefore had a higher binding constant (KA ) and a larger number of binding sites (n). The addition of GA could also improve protein solubility and emulsifying ability. The emulsions prepared with complexes, especially the complex of GA and SPH obtained by pepsin hydrolysis for 3 h, had a high absolute charge value, uniform particle size distribution, stable morphology, and good storage stability. After storage, the emulsification index (CI) of the emulsion only increased to 23.08%; its 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity was 24.37 ± 1.22% and its 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS+ ) free radical scavenging activity was largely retained.During long-term storage, pepsin-treated protein (especially protein treated for 3 h) and GA can form a stable emulsion with antioxidant properties. This work provides new ideas for the development of natural and safe emulsifiers that have antioxidant properties and can be stored long-term and used in the food industry. © 2022 Society of Chemical Industry.