A study on tailoring protein interactions to influence the functional properties of milk protein concentrate powders

Abstract

Milk protein concentrate (MPC) powders are milk-derived ingredients that are highly functional and provide a wide range of nutritional and functional benefits in food product applications. High protein MPC powders are good for protein enhancement while giving a clean dairy flavor without the addition of lactose to product formulations. Besides protein enrichment and nutritional benefits, MPC powders provide functional properties like gelling, emulsification, foaming, and thickening to name a few. The functional properties of milk protein concentrates are correlated with their protein content and protein-protein interactions which in turn is a gateway for a wide range of product applications in the food industry. Various processing methods have been studied to improve the functionality of milk proteins. Heat treatment and pH adjustment separately have been widely used to modify and bring about changes in the functionality of milk proteins. As the initial step in this research study, MPC powders were manufactured from skim milk which was heated at varying pH. The protein fractions of the resultant MPC powders were analyzed using capillary electrophoresis to determine the protein-protein interactions at serum and micellar phases. Increased casein-whey protein interaction was observed at lower pH while higher levels of soluble whey proteins (bound and unbound) were found at a lower pH. This significantly (p<0.05) improved the heat stability of the resultant powders as well as a change in viscosity with respect to pH change. In the study that followed, the same MPC powders were used for gelation studies. The rheological characteristics and gel parameters of the MPC powders were studied with respect to the protein interactions observed in the previous study. MPC powders with heated skim milk bases showed early onset of gelation but were not significantly different (P<0.05) with respect to the varying pH. The G′ was lowest for samples at pH 6.5 leading to the formation of a weaker gel, while at pH 7.1 the gel structure was stronger. The network structure of the gel became denser and less porous as the heating pH increased. Therefore, it can be concluded that tailoring protein-protein interactions by altering processing conditions during the manufacture of MPC powders brings about desirable changes in their functionality. These changes not only open possibilities for MPCs as a dairy ingredient but also in other untapped product applications.