Influence of microbial transglutaminase cross-linking on gelation kinetics and texture of acid gels made from whole goats and cows milk

Abstract

The influence of microbial transglutaminase (mTGase) in modifying the functionality of proteins in cows milk has been extensively studied but to a lesser degree for goats milk. On a comparative basis, the effect of cross-linking by mTGase on the physical properties of chemically acidified UHT goats milk and UHT cows milk has been performed. Transglutaminase treatment (3 U mTGase/g protein) of cows and goats milk was conducted at 40 °C for 60 min and terminated by heat treatment (85 °C/10 min) for enzyme inactivation. Gelation was induced by acidification with 40 g.L−1d-glucono-δ-lactone. Monitoring gel formation by oscillatory rheometry revealed that the incubation of milk with mTGase accelerated gelation, which occurred at a higher pH for cows milk in comparison to goats milk. Electrophoretic analysis revealed that under the same conditions, nearly 31% of the cows milk proteins were cross-linked by the action of mTGase compared to only 9.6% of the goats milk proteins. This resulted in increased gel stiffness and reduced syneresis of the acid gels of both systems, but the extent of the effect depended on the milk source. In general, even with the mTGase treatment, goats milk gels were much weaker than cows milk gels. Despite this fact, the information gained in this study indicates that mTGase might be successfully applied in the production of acidified goat milk products.