Effect of oxidization and chitosan on the surface activity of soy protein isolate

• The structure of soy protein isolates were changed by the performic acid.
• Based on the changed structure, chitosan reacted with the soy protein isolates.
• The emulsifying capacity of the composites increased substantially.
• The structure of the oxidized composites changed a lot compared to the pure one.

The objective of this research was to study the effect of oxidization of performic acid and chitosan on the structure and surface properties of soy protein isolate. As the degree of oxidization increased, the emulsifying capacity and stability of all the oxidized soy protein isolate and chitosan (SPI/CHI) systems increased substantially, which were 29.7%, 31.7%, 34.1%, 31.9% and 31.9% respectively compared. Fluorescent spectrum showed that the fluorescence intensity of SPI/CHI conjugates decreased and the higher the oxidized degree was, the lower the fluorescence intensity. Results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the location of acidic bands of SPI/CHI conjugates moved upwards and broadened. Meanwhile, the basic bands lightened or even disappeared gradually as the oxidization increased. Scanning electron microscope (SEM) showed that the particles became lager as the degree of oxidization increased. Better thermostability of the oxidized SPI/CHI systems was shown in the differential scanning calorimetry (DSC).