Influence of treatments on hydrated milk protein concentrate particles and resulting cast feta cheese characteristics

Milk protein concentrate (MPC) is a relatively new food ingredient which contains both casein and whey proteins. Due to its protein composition, MPC can provide various functional properties in a food system as well as improve the nutritional value of the food products. However, one of the most economically feasible applications of MPC is in the cheese-making industry, especially where the milk supply is limited.; Recombined milk fat and 56% MPC is used for cheese-making in some areas outside of the United States. MPC with protein content higher than 60% has been reported to be difficult to use in cheese-making, including cast Feta cheese production.; A hypothesis of shell formation during spray-drying of MPC particle that affected the properties of the MPC particles was proposed. The objectives of this study were to provide an understanding of the MPC particle variability related to the functionalities of the MPC in rennet coagulation and cheese-making, and to investigate means to improve the cheese-making properties of commercially available high protein content MPCs.; High protein content MPC samples tended to have a large particle size. All the MPC samples with protein content higher than 50% had a particle size larger than 20 um. Ultrasonication, heat, and shear treatment by homogenization were some of the effective ways to dissociate the particles. A combination of two treatments provided synergistic effects on dissociating particles.; Addition of CaCl2 was needed for the MPC solution to form a rennet-induced gel. The gel strength was affected by the treatments of the MPC solution, as well as the added rennet and calcium concentrations. Generally, the correlation between the MPC hydrated particle size and the resulting rennet gel strength was negative.; There was no good correlation between the hydrated MPC particle size and the hardness of the resulting cheese. However, the MPC85 cheese was significantly softer than its MPC56 counterpart. The pH of the cheese had a large impact on the cheese texture. Addition of lactose into the MPC85 cheese milk reduced the pH of the cheese and improved cheese hardness. The ESEM examination of surface microstructure revealed differences between MPC cheese samples.