Impact of the dairy product structure and protein nature on the proteolysis and amino acid bioaccessiblity during in vitro digestion

Abstract

Elderly people exhibit specific nutritional needs, in particular they require higher protein intake. The objective of this study was to compare, using an in vitro digestion protocol, the nutritional performance of novel dairy products, based on whey proteins and which mimicked different commercial cheese textures. Whey proteins have replaced caseins in these different gels for their known ability to promote muscle synthesis in the elderly thanks to their high amount of leucine.The hydrolysis of proteins and the bioaccessibility of amino acids have been evaluated from the simulated gastro-intestinal digestion of four whey-based products of identical composition but different structural properties. Heat-induced gelation of a whey-based dairy emulsion was performed by applying different combination of pH, stirring and heat treatment, in order to obtain a range of different gel structures, from liquid to more or less firm and or whipped gels. A commercial Mozzarella cheese has been tested as the casein-based control.Results showed that both the kinetics of protein hydrolysis and the amino acid release were significantly higher in the casein-based gel than in whey protein matrices. The extent of protein hydrolysis was higher in the whey protein gels compared to the liquid control sample, due to a facilitated hydrolysis of the heat-denatured proteins compared to native proteins. Peptide release and amino acid bioaccessibility were however not significantly influenced by the matrix structure. Further studies, using an in vivo digestion model will allow assessing the amino acids bioavailability of these matrices.