Abstract:In order to study and measure the changes of the emulsifying properties of sweet potato protein hydrolyzates obtained by enzymatic treatment under high hydrostatic pressure,Proreinase.K, Alcalase, AS1.398, Neutrase and Papain were selected, and the mixed liquors of sweet potato protein and each of the above mentioned 5 enzymes were treated under four pressures (100, 200, 300 and 400 MPa) at the optimal temperature and pH conditions for the enzyme activities for 4 min respectively. Then the degree of hydrolysis, microstructure of emulsion, emulsifying activity index (EAI) and emulsion stability index (ESI) of the supernatant were measured. The results showed that, compared with ordinary pressure, the degree of hydrolysis of the sweet potato protein hydrolyzates under high hydrostatic pressure increased significantly. The particles of emulsions became more fine and uniform except Alcalase. Besides, the EAI of other four hydrolyzates emulsions increased significantly, of which the EAI of hydrolyzates treated by Papain under 300MPa reached the maximum of 101.59 m2·g-1. While the ESI of sweet potato protein hydrolyzates which treated under high hydrostatic pressure all increased compared with that under ordinary pressure, and the ESI of hydrolyzates treated by Neutrase under 300MPa reached the maximum of 75.80 min. Furthermore, when the sweet potato protein was treated with Papain (pH 7,55℃) under 300MPa which condition the EAI was the highest for 6 min, the EAI and ESI of the hydrolyzates reached the maximum of 129.58 m2·g-1 and 21.98 min, respectively. This study provides a basic theoretical support for the application of sweet potato protein as an emulsifier in food industry.