The effect of transglutaminase on colloidal stability of milk proteins

Food industry is on constant search for improved, enzymatically modified forms of proteins, which are the most important functional food ingredients, capable of either introducing or modifying texture, appearance, and flavour. One of the key aspects of food design is creating new functional properties and novel food macro- and microstructures in order to provide tailored food characteristics expected by consumers. Milk proteins are among the most thoroughly studied protein complexes occurring in foods and having a wide range of functionalities. The common usage of milk proteins has also contributed to the development of techniques designed to modify and improve functional properties of milk proteins. The aim of this study was to investigate the impact of enzymatic modification induced by microbial transglutaminase (TGM) in milk proteins on the range of cross-linking as well as heat and ethanol stability of these proteins. Milk used in the study was subjected to various technological processes and then incubated with the enzyme added at an amount of 2 Units g−1 protein for 2 h at 40 °C. Modification of milk proteins by transglutaminase leads to their partial cross-linking and formation of high molecular weight polymers in the range of 55–200 kDa. The changes of cross-links between milk proteins occur most dynamically in the first hour of incubation at 40 °C. Enzymatic modification of milk proteins significantly increases the ethanol stability of raw as well as pasteurized milk and UF concentrate. Addition of transglutaminase does not change the heat stability of milk measured as the time of heat coagulation at 140 °C.