Influence of different functional ingredients on physical properties, rheology, tribology, and oral perceptions of no fat stirred yoghurt.

Effects of adding four functional ingredients: inulin, pectin, galacto-oligosaccharides (GOS), and beta glucan on physical, rheology, tribology, and sensory characteristics of skim (0.1% fat) stirred yoghurt were studied. Three levels of each ingredient were chosen: inulin (7, 8, and 9%), pectin (0.2, 0.25, and 0.3%), GOS (9.1, 11.3, and 13.6%), and beta glucan (0.1, 0.2, and 0.3%). Among the investigated ingredients, inulin and GOS appeared to be preferable choices due to their ability to both reduce syneresis and slightly increase sample lubrication while maintaining texture, rheology, and sensory characteristics of skim yoghurt. Pectin and beta glucan, conversely, increased viscosity and gel strength, slightly increased sample lubrication for the skim yoghurt but created large particles (i.e., greater than 100 µm) in the product body. This led to the increase in lumpiness and residual coating while reducing smoothness and creaminess of the sample. The observed tribology behaviors of the stirred yoghurts were similar to the previous study of pot-set yoghurt whose friction curves comprised four friction zones (Nguyen, Kravchuk, Bhandari, and Prakash). The sensory characteristics of six selected samples for various texture and mouthfeel attributes obtained from a trained panel were in agreement with particle size, rheology, and tribology characteristics of the yoghurt samples. PRACTICAL APPLICATIONS: With the increasing demand for low fat and functional food, there is a need to understand the impact of adding functional ingredients in low fat yoghurt to satisfy consumers' requirements. This study investigates the effects of these functional ingredients at different dosages on physical, rheology, tribology, and sensory characteristics of skim (0.1% fat) stirred yoghurt. The results from this study may guide use of functional ingredients in yoghurt production.