Physicochemical Properties and Surface Activities of Collagen Hydrolysate-Based Surfactants with Varied Oleoyl Group Grafting Degree

A series of collagen hydrolysate-based surfactants (CHBS) were prepared by grafting different amount of oleoyl group onto collagen hydrolysate (CH). Their physicochemical properties and surface activities were investigated, and their emulsifying ability on rapeseed oil water emulsion was evaluated. The results showed that, as increasing grafting degree of oleoyl group, the free amino content and isoelectric point of CHBSs and the size of CHBS particles formed in aqueous solution declined, while their molecular weight and surface hydrophobicity increased. The CHBSs with high grafting degree, such as CHBS-30, CHBS-40, and CHBS-50 (postfix datum represents mmol amount of oleic acid chloride to react with 10 g collagen hydrolysate), exhibited satisfactory wetting capacity and foaming capacity, and the CHBSs with low grafting degree, such as CHBS-10 and CHBS-20, presented good emulsifying capacity. The surface activity of CHBSs was closely correlated with the hydrophobicity of their molecules, as well as their capacity to reduce the surface tension of air water interface. In addition, CHBS-20 showed good emulsifying ability on rapeseed oil water emulsion in neutral and alkaline pH, even in the condition of low salt concentration.