Emulsifying properties of conjugates formed between whey protein isolate and subcritical-water hydrolyzed pectin.

Abstract This work aimed to evaluate the feasibility of subcritical water-hydrolyzed pectin from passion fruit (Passiflora edulis) peel for improving emulsifying property of whey protein at pH near its isoelectric point. The hydrolyzed pectin with different molecular weights (20, 77, and 146 kDa) were conjugated with whey protein isolate by a dry-heating method at 80 °C, 79% RH, for 6, 24, and 48 h. Soluble fraction after the conjugation was analyzed for conjugated molecules by SDS-PAGE and fluorescence spectroscopy. SDS-PAGE showed polydisperse bands from 15 to 250 kDa, which indicated that whey protein isolate-pectin conjugates were formed. Fluorescence spectroscopy also revealed that the highest conjugates yield was obtained from the conjugation with 146 kDa pectin at 6 h. These conjugates were used as emulsifiers in oil-in-water emulsions containing 5% w/w of medium-chain triacylglycerol in an aqueous phase at pH of 5. The smallest oil-droplet size and most stable emulsion was also obtained using the conjugates at 6 h of the dry-heating. Moreover, the conjugates from larger pectins showed significantly higher emulsion stability. Graphical abstract Image 10971 Highlights • The conjugates were tested as emulsifiers and could give small oil-droplet sizes <1.0 μm. • Emulsions showed excellent stability albeit they were prepared at near pI of WPI. • The most stable emulsion was obtained using the conjugates at 6 h of dry-heating. [ABSTRACT FROM AUTHOR]