Steady, dynamic, creep/recovery, and textural properties of yoghurt/molasses blends: Temperature sweep tests and applicability of Cox-Merz rule

Abstract

In this study, physicochemical, rheological (steady, dynamic, and creep/recovery), and textural properties of yoghurt/molasses blends (0, 5, 10, and 15% molasses) were investigated. The blends showed shear thinning behavior, as described by Ostwald de Waele model (R-2 >= 0.955). Consistency coefficient value (K) of the blends decreased with increasing molasses concentration in the sample. Storage modulus (G') of blends was higher than loss modulus (G ''), exhibiting weak gel-like behavior. Molasses addition decreased G' and G '' values. Temperature sweep tests indicated that blends followed Arrhenius relationship. A modified Cox-Merz rule was applicable using shift factors. Compliance values (J(t)) increased as molasses concentration increased, revealing that deformation stability and internal viscosity (eta(1)) decreased with concentration. Creep behavior was characterized using Burger model. Obtained J data as a function of time could be satisfactorily fitted to Burger model (R-2 >= 0.994). The final percentage recovery of blends remarkably decreased with the increase of molasses concentration. Firmness, consistency, cohesiveness, and viscosity index values decreased with molasses addition. According to the results of the current study, molasses amount to be added to the yoghurt should be determined regarding rheological properties since resistance of the sample to deformation decreased with increase in molasses concentration.