Studies on Rheological Properties of Stirred Milk Gels Made from Milk with Defined Genetic Variants of κ-Casein and β-Lactoglobulin

The rheological properties of acidified milk gels made from milk with defined genetic variants of κ-casein and β-lactoglobulin have been investigated. Gels were prepared from skim milk after heating for 4 min at 90°C by acidification with glucono-δ-lactone and gentle stirring after holding for 24 h at 20°C. Stirred acidified milk gels were then kept at 6°C for 96 h and thereafter measured for the rheological properties using a Bohlin VOR Rheometer. The milk gels containing only the B variant of β-lactoglobulin (homozygous cows) were found to have a significantly higher elastic modulus as compared to milk gels containing both β-lactoglobulin A and B or only A. An explanation could be that more β-lactoglobulin B had aggregated with the casein micelles, since a strong correlation was found between the loss of native β-lactoglobulin in the milk serum and the gel firmness. No correlation was found between gel firmness and any of the κ-casein genetic variants, dry matter content and the total protein concentration, respectively. Furthermore, viscous properties did not vary between the acidified milk gels in this experiment.