Effect of Hydrolysis Degree on Structural and Interfacial Properties of Sunflower Protein Isolates

The effect of different degree of hydrolysis (DH) by Alcalase on the structural and interfacial properties of sunflower protein isolates was investigated. Sunflower protein isolates were extracted from defatted sunflower flour and hydrolyzed by Alcalase by applying different DH (low [10%], medium [20%] and high [30%]). Size exclusion chromatography results showed that the sunflower protein hydrolysates with different low molecular mass distribution were detected. Circular dichroism analysis showed the hydrolysates possessed a decreased -helix but higher -turn and random coil structures. The analysis of intrinsic fluorescence spectra indicated a moveable tertiary conformation of the hydrolysates. In comparison with sunflower protein isolate, its hydrolysates showed higher foaming activity and emulsion stability, but the foams were unstable and the emulsifying activity index was decreased. The hydrolysis significantly modified the structural and interfacial properties of the sunflower protein isolate. Practical ApplicationsThe structural and interfacial properties of sunflower protein isolates were remarkably modified by the Alcalase hydrolysis with the DH range of 10-30%. The hydrolysates exhibited relatively higher foaming capacity and emulsion stability index. Limited hydrolysis and excessive hydrolysis of sunflower protein isolates can enhance foaming capacity and emulsion stability of the products. Thus it was demonstrated that by controlling DH of sunflower protein isolates, hydrolysate with a desirable functional properties can be obtained.