Whey protein isolate—low methoxyl pectin coacervates as a high internal phase Pickering emulsion stabilizer

The application of whey protein isolate (WPI)–low methoxyl pectin (LMP) particles generated by complex coacervation as a food-grade high internal phase Pickering emulsion (HIPE) stabilizer was investigated. The coacervation pH greatly influenced the emulsification ability of the resultant WPI–LMP particles and those separated in pH 3.5 could generate a HIPE with oil fraction of up to 79.02%, which could be ascribed to their small particle size and moderate contact angle. The emulsification ability of the WPI–LMP coacervates was quite sensitive to ionic strength and their concentration, in which, HIPEs could be fabricated only in the absence of NaCl and stabilizer concentration 1.5% (w/v) or higher. The HIPEs showed decreased droplet size with WPI–LMP coacervate concentration rise and were of the oil-in-water type according to confocal laser scanning microscope observation. The HIPEs stabilized by the WPI–LMP coacervates were stable only in solutions with pH of 4.0 or lower and were resistant to centrifugation and heating, but collapsed readily upon freezing and thawing; meanwhile, a higher stabilizer concentration conferred better stabilities. Hence, the WPI–LMP coacervates could find potential applications in the food industry as a HIPE stabilizer.