Transglutaminase: effect on rheological properties, microstructure and permeability of set style acid skim milk gel

Abstract

Reconstituted skim milk was incubated with microbial transglutaminase to allow enzymatic cross-linking of the milk proteins. Subsequently the cross-linked skim milk was acidified by glucono-δ-lactone. Three methods were applied to study the nature of the gels. A Bohlin VOR rheometer was used to follow the development of rheological properties during acidification; gel permeability was determined by measuring liquid flow through the gel; and the microstructure of the gels was investigated by confocal laser scanning microscopy (CLSM). It was found that skim milk incubated with transglutaminase formed a 4- to 6-fold suffer gel with a 2- to 3-fold lower permeability on acidification than gels without transglutaminase. Images from CLSM revealed that skim milk gels with transglutaminase have a finer protein network with thin strands between the particles than the untreated acid skim milk gels, which were found to consist of coarser particles.