Effects of composition, temperature and shear rate on chocolate milk rheology: an empirical modeling approach incorporating yield behavior

Abstract This study elucidates the effects of composition and temperature on the rheological behavior of chocolate milk formulation. The fat [0.5, 1 and 1.5 g] and xanthan gum contents [0.05, 0.1 and 0.15 g] varied and shear stress-strain rate data were recorded at varying temperature [21.4, 65 and 80 °C]. All compositions showed predominantly a pseudoplastic behavior [i.e., pseudoplasticity index, n < 1] with a strong influence on composition and temperature. Three semi-empirical rheological models, i.e. Power-law, Herschel–Bulkely, and Casson models were fitted on the data using an in-house developed computer program for the best statistical fit. The pseudoplasticity index [ n ] varied with the composition that initially decreased with temperature and subsequently increased. The other model parameters such as consistency index [ k ], Casson and Herschel–Bulkely yield stress, and Casson viscosity [at a specified rate i.e., 34.7 s −1 ] were computed through model fitting and correlated to the microstructural changes inside the fluid keeping in view the composition and temperature. This study helps in correlating chocolate milk processing and quality control based on complex microstructure to the rheological parameters measured at simulated temperatures and shear rates.