Components of Vane Yield Stress of Structured Food Dispersions

Abstract

The vane technique was used to determine the static (s0s) and dynamic (s0d) yield stresses of six commercial foods: mayonnaise, mustard, ketchup, applesauce, and two brands of tomato puree (samples TD and TR). The samples, other than TR, exhibited shear-thinning behavior. For those samples, based on a model proposed earlier, the contributions of bonding (sb), network (sn), and viscous (sv) to yield stress of the products were determined. For the homogenized products, sb > sn, while for those processed in a finisher sn > sb. Because sample TR exhibited shear-thickening behavior, the model to estimate yield stress components was not applicable. The structural conditions necessary for the validity of the proposed model are established. Equilibrium stress (s¥) values obtained by extrapolation of vane torque data to infinite time were comparable to s0d values.