Rheological properties of poppy seed paste/grape pekmez blends

Abstract

Rheological properties of poppy seed paste (PSP)/grape pekmez blends containing 10%, 15%, 20%, 25%, 30%, 35%, and 40% PSP were determined at different temperatures (10–40 °C). The PSP/grape pekmez blends behaved as a pseudoplastic fluid. The flow behavior index of the blends containing 10% PSP varied between 0.92 and 1.0, however, as the concentration of PSP increased to 40% the flow behavior index decreased to the range of 0.23–0.67. As the temperature increased the viscosity and the consistency coefficient (K) decreased. The activation energies (Ea) of the blends were found in the range of 23,054.8–66,059.1 kJ/kmol. The consistency coefficient increased from the range of 0.25–3.56 Pa sn to 35.63–203.01 Pa sn as the PSP concentration increased from 10% to 40%. The combined effect of the concentration, temperature and shear rate on the viscosity of the PSP/grape pekmez blends were described successfully by a simple equation. The blends showed a rheopectic time-dependent behavior. Practical applications: Rheological properties of fluid foods are necessary for designing and evaluation of food processing lines, quality control and consumer acceptability. In this study, flow behavior and the effect of temperature and PSP concentration on the rheological properties of the PSP/grape pekmez blends were determined. The effect of concentration, temperature, and shear rate on viscosity was represented by a simple equation which can be used in engineering calculations. Time-dependent flow behavior of the PSP/grape pekmez blends was also determined that it is important for the estimation of changes in the flow behavior during processing. © 2017 Wiley Periodicals, Inc.