Influence of transglutaminase-induced modification of milk protein concentrate (MPC) on yoghurt texture

This study evaluated the effect of transglutaminase (TGase) treatment on the textural properties of acid-induced milk protein concentrate (MPC) gel and yoghurt fortified with modified MPC. The effects of reaction duration, pH, temperature, and enzyme concentration on the strength and water-holding capacity (WHC) of MPC (72% protein) gel were analysed. The gelling mechanism of modified MPC was explored and the modified MPC was incorporated into production of stirred-style yoghurt. Optimal MPC gel properties were achieved after TGase treatment at pH 7.25 and 35 °C for 1 h using 2.5 U g−1 TGase. The TGase-induced reaction occurred quickly in the first 0.5 h and led to the formation of large particles with fairly uniform size (from 100 to 1000 nm). All the κ-casein and 61.7% of the β-casein participated in the reaction. Modified MPC greatly enhanced the gel quality of the yoghurt in terms of gel strength, viscosity, WHC and serum-binding capacity.