Effects of β-Lactoglobulin on the Rheological Properties of Casein Micelle Rennet Gels

The effects of heat treatment on the gelation properties of casein micelle suspensions in the presence or absence of β-LG were studied using a rheolograph-sol apparatus, scanning electron microscopy, and transmission electron microscopy. In the absence of β-LG, the characteristic parameters of the gelation curves (gel modulus, gelation time, and gelation rate) changed slightly as temperature increased from 65 to 80°C. In the presence of β-LG, the three parameters were strongly dependent on the temperature of the treatment; the gel modulus and the gelation rate at 80°C were about 50 and 12.5%, respectively, of the values found at 65°C. After heat treatment at various temperatures, the amounts of β-LG in the ultracentrifugal supernatant of the samples were estimated; the amounts of β-LG decreased as temperature of heat treatment increased. This result may mean that complex formation by interaction between β-LG and κ-CN is occurring. The microstructures showed many fine grains on the surface of casein micelles when the samples were heated with β-LG.