Effects of ultrasound treatment on physico‐chemical, functional properties and antioxidant activity of whey protein isolate in the presence of calcium lactate

Abstract BACKGROUND The aim of this study was to investigate the effects of ultrasound applied at various powers (0, 200, 400, 600 or 800 W) and for different times (20 or 40 min) on the physico‐chemical, functional properties and antioxidant activities of whey protein isolate (WPI) dispersions in the presence of 1.20 mmol L −1 calcium lactate. RESULTS Surface hydrophobicity and free sulfhydryl group of the WPI dispersions containing 1.2 mmol L −1 calcium lactate were significantly enhanced after sonication. Furthermore, particle size of WPI dispersions containing 1.20 mmol L −1 calcium lactate was minimised after sonication. Scanning electron microscopy of sonicated WPI suspensions containing 1.20 mmol L −1 calcium lactate showed that WPI microstructure had significantly changed. After WPI dispersions were treated by sonication assisted with calcium lactate, its gel strength enhanced and solubility decreased. Gel strength of sonicated WPI dispersions (600 W, 40 min) was the maximum among all the WPI treatments. Emulsification activity of sonicated WPI dispersions reduced while its emulsion stability increased. The DPPH radical scavenging activity and ferrous reducing power of sonicated WPI dispersions mostly increased. CONCLUSION Ultrasound treatments induced structural changes in WPI molecules, leading to different microstructure and improved gel strength of WPI in the presence of calcium lactate. © 2017 Society of Chemical Industry