Relation between sensory texture analysis and rheological properties of stirred yogurt

The sensory and rheological characteristics of stirred yogurts varying in fermentation temperature, heat treatment of milk, dry matter content and composition of bacterial cultures were investigated. Two independent sensory properties, non-oral viscosity and oral viscosity, were evaluated. To reflect these properties precisely it was necessary to perform rheological measurements at both small and large deformations. Non-oral and oral viscosities were successfully modelled from a set of rheological variables by partial least squares regression, resulting in a three component model explaining 83.8% of the variation in non-oral viscosity and a two component model explaining 82.0% of the variation in oral viscosity. Non-oral viscosity was highly correlated with the complex modulus (G*) from the dynamic oscillatory measurements (r = 0.823) and the viscosity obtained from a Brookfield viscometer (with Helipath stand) operating at 5 rev./min (r = 0.862). Similarly, there were relationships between oral viscosity and the hysteresis loop area from the viscometry test (r = 0.867) and between oral viscosity and the viscosity obtained from the Posthumus funnel (r = 0.834).