Rheological predictions of sensory attributes of lotions.

Complex behavior of 33 commercial lotions was investigated in order to identify correlations between laboratory instrumental measurements and sensory attributes of these products. Sensory attributes were evaluated by trained panelists. Six attributes were identified as potentially related to rheology, which belong to three main sensory categories: appearance, pickup, and rub out. Potential rheological predictors were extracted from the data of rotational rheometry. Yield stress and instantaneous viscosity maximum (IVM) were determined in stress ramp. Alternative definitions of yield stress based on step-shear and oscillatory strain sweeps were also considered along with linear viscoelastic moduli, G' and G″. Statistical analysis has shown all these definitions of yield stress and IVM are in fact closely correlated and that IVM is the best overall predictor of most attributes although G'/G″ ratio also is significant for rub out attributes. However, integrity of shape, the main appearance attribute, is even better predicted by an imitative slump-like test in which image analysis is used to quantify sample spreading on a flat surface.