Structural and Functional Changes in Ultrasonicated Oyster Protein Isolates

Structural and functional changes in ultrasonicated oyster protein isolates (OPI) were investigated. Ultrasound treatments were carried out with probe (20 kHz) at 200, 400 and 600 W for 15 and 30 min. The results showed that functional properties of OPI significantly improved after sonication. Absolute zeta potential and protein solubility increased by 18.40 mV and 82.5 % at 600 W for 15 min. Oil holding capacity, emulsifying activity index, emulsion stability index, foaming ability and foaming stability increased by 300 %,15.23 m(2)/g, 9.24 min, 23.9 % and 14.8 % at 600 W for 30 min. However, ultrasound treatment significantly (P < 0.05) decreased particle size and water holding capacity. The conformation of OPI became stretched and unfolded after sonication. Functional improvements resulted from stretched and unfolded conformation and reduction of particle size. Controlled condition of ultrasound can produce OPI with distinct structural and functional properties, which could meet the complex needs of manufactured food products in food industry, but further study is needed to understand the specific mechanism.