Physicochemical properties of yoghurt supplemented with polymerized whey protein and inulin

Polymerized whey protein (PWP) and inulin are important functional biopolymers, but their combined use in yoghurt system has not been studied. The present study was carried out to investigate the effect of combination of PWP (2%-4.5%, w/v) with inulin (0.5%-3%, w/v) on the physicochemical properties of yoghurt. During yoghurt fermentation, the yoghurt of the group PWPIY5 containing the highest concentration of PWP (4.5%, w/ v) but lowest inulin (0.5%, w/v) could efficiently form stable yoghurt gel as indicated by the fast acid formation with the highest titratable acidity of 0.72 +/- 0.02% at 5 h, and best micro-rheological properties with the highest elasticity and lowest fluidity. Furthermore, PWPIY5 exhibited the best fine-textured yoghurt in terms of hardness, smoothness and particle size distribution, and the best viscosity properties with the least syneresis among all the experimental groups. Scanning electron microscopy confirmed the more homogeneous protein aggregates and denser network structure with smaller pores in the yoghurt of PWPIY5. Therefore, combination of PWP with inulin represents great potential to be explored in functional fortified yoghurt with improved physicochemical and functional properties.