Cross-linking casein micelles by a microbial transglutaminase: influence of cross-links in acid-induced gelation

Mechanical and structural properties of transglutaminase-induced casein gels are described here and compared with those of traditional acid casein gels. These gels were characterised by rheology and microscopy (confocal laser scanning microscopy and transmission electron microscopy). Unlike traditional casein gels produced by acidification and/or renneting which lead to gels cross-linked by weak physical interactions, gels formed using transglutaminase are covalently cross-linked. Gels with different characteristics can therefore be formed in this way and have some unusual and interesting features in terms of strength, kinetics of gelation, sensitivity to heat treatment and syneresis behaviour. The first steps of the transglutaminase-induced micellar aggregation were followed by turbidimetry and a mechanism for the aggregation process proposed.