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

¹ Department of Bioscience and Chemistry, Faculty of Agriculture, University of Hokkaido, Sapporo 060, Japan
² Department of Polymer Science, Faculty of Science, University of Hokkaido, Sapporo 060, Japan

The effects of heat treatment on the gelation properties of casein micelle suspensions in the presence or absence of ß-LG were studied using a rheolograph-sol apparatus, scanning electron microscopy, and transmission electron microscopy. In the absence of ß-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 ß-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 ß-LG in the ultracentrifugal supernatant of the samples were estimated; the amounts of ß-LG decreased as temperature of heat treatment increased. This result may mean that complex formation by interaction between ß-LG and -CN is occurring. The microstructures showed many fine grains on the surface of casein micelles when the samples were heated with ß-LG.

Key Words: casein micelles • ßbeta;-lactoglobulin • rheology • rennet gels

Submitted on August 31, 1995
Accepted on July 1, 1996