Investigating the effect of whey protein-starch conjugate on quality attributes of oil-in-water emulsion

Whey proteins are of wide application in the formation and stabilization of food emulsions. However، due to their high sensitivity to environmental conditions they quickly lose their functional properties. Glycolation of whey protein fractions is one of the methods used to modify their structure and improve their functional characteristics. The present work was carried out with the aim to prepare whey protein- starch conjugates and investigate the effect of protein to polysaccharide ratio on the quality attributes of oil-in-water emulsion. The results indicated that surface electrical charge decreased by increasing starch to protein ratio. On the other hand، changes in the surface and interfacial tension did not follow a clear trend in response to altering the mass ratio of protein. The drop size distribution curves were monomodal and nearly normal for all samples and became noticeably sharp with minimum width at protein to starch ratio 1:1. The finest and largest droplets were observed in the aforementioned sample and the one stabilized by modified starch، respectively. Studying the flow behavior of emulsions also revealed that starch containing sample exhibited the characteristics of near-Newtonian fluid، whilst the others were shown to have shear thinning pseudoplastic properties which became more distinct by increasing protein ratio leading to highest consistency index and lowest flow behavior index at %100 whey protein.