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Keywords:

  • yield stress;
  • vane method;
  • static yield stress;
  • dynamic yield stress;
  • bonding;
  • network;
  • viscous

ABSTRACT:

The vane technique was used to determine the static (σos) and dynamic (σ0d) yield stresses of 6 commercial foods: mayonnaise, mustard, ketchup, applesauce, and 2 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 (σ-b), network (σ-n), and viscous (σv to yield stress of the products were determined. For the homogenized products, σb > σn, whereas for those processed in a finisher, σn > σb. 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 (σ) values obtained by extrapolation of vane torque data to infinite time were comparable to σ0d values.