Effect of different hydrocolloids on texture, rheology, tribology and sensory perception of texture and mouthfeel of low-fat pot-set yoghurt

A systematic study on the effect of some commonly used hydrocolloids in yoghurt formulation, namely gelatin (0.5–1.5%), xanthan gum (0.005–0.015%), carrageenan (0.01–0.08%) and modified starch (0.5–1.5%) on the physical, tribology and sensory characteristics of skim pot-set yoghurt (0.1% fat) is presented. The results support to develop a tribology model for yoghurt, which can be directly correlated with the scores on texture and mouthfeel attributes from sensory panel by mean of statistical analysis. The tribological behavior, which signifies the lubrication property of the product, depended on the fat content, the type and dosage of hydrocolloid. Among the four hydrocolloids investigated, gelatin appeared to be the best hydrocolloid due to its ability to reduce syneresis, increase texture, viscosity, gel strength and lubrication properties of skim yoghurt. As a result, its sensory perception was significantly improved and attained the same sensory scores with full fat yoghurt for various desired sensory attributes, such as thickness, smoothness and creaminess. Both xanthan gum and carrageenan increased the firmness and viscosity of skim yoghurt, but also significantly increased the syneresis and undesired sensory mouthfeel characteristics, such as chalkiness and lumpiness. Modified starch slightly improved lubrication properties and thickness of skim yoghurt without significant changes in the product texture. From tribological analysis of investigated samples, a four-zone tribology model for yoghurt was proposed. Each zone corresponds to different mechanisms of fluid entrained between the two contact surfaces. The tribology behavior of the yoghurt fluid, therefore, can be represented by the position of each transition point and the slope of each friction zone, which were aligned with the sensory scores from trained panel.