Effect of the Compositional Factors and Processing Conditions on the Creaming Reaction During Process Cheese Manufacturing

Selected influencing factors in processed cheese making (protein and fat content, fat globule size, and rework addition) affecting the physical changes known as “creaming” were investigated for their effect on this multistage structure formation reaction. The creaming curve (viscosity vs. time) shows four typical stages: an initiation phase, a first exponential stage, a plateau, and a second exponential phase. Increasing the protein content from 10 to 17% (w/w) accelerated the reaction. Light microscopy showed that the fat content (0–20%) affected the shape of the creaming curve as well and it was shown that a fat level of 15–20% is required for the characteristic creaming curve to occur. Moreover, modifications in the initial milkfat globule size (3.7 μm down to 1.1 μm) by means of upstream homogenization (0–250/50 bar) accelerated the exponential phase and modified the shape of the creaming curve, shortening the initiation and plateau phases. The reaction started earlier with decreasing incoming fat globule size, and the slope was steeper. When fat was present in the system, it was not only the content, but the milkfat globule size which dictates the viscosity change and shape of the curve. The addition of rework dramatically affects the structure formation process, rework probably acting as a catalyst accelerating the reaction. However, protein polymerization was found to be constant during the entire course of the reaction suggesting that weaker physical bonds are responsible for the structuring of the matrix.