Effects of high hydrostatic pressure sterilisation and thermal sterilisation combined with glutamine transaminase treatment on the properties of yoghurt

Abstract

The effects of conventional thermal sterilisation and high hydrostatic pressure (HHP) sterilisation combined with glutamine transaminase (TGase) on the characteristics of set yoghurt were investigated. Upon thermal and HHP treatment, the addition of an appropriate amount of TGase had no significant effect on the acidity and viable bacteria count of the yoghurt. However, the water holding capacity, viscosity, and firmness of the yoghurt significantly improved. When yoghurt was thermal treated combined with TGase and with HHP followed by TGase, the optimal values of the yoghurt indicators were achieved when 2 U g−1 TGase was added. When TGase was added at 4 U g−1 before HHP treatment (TGase-HHP), the optimal values of the yoghurt indicators were achieved. It was clear that the proteins in TGase-HHP yoghurt exposed more TGase binding sites than the other two types of treatment. In addition, tests were performed with chroma meters, electronic tongues and electronic noses.