Effect of processing, preservation and storage on rheology of guava pulp

Abstract

Rheological behavior of white and pink guava pulps was investigated using Rheotest 2 coaxial cylinder viscometer over shear rates of 0.6 to 145.8 s-1. The shear rate-shear stress data followed the power law, Casson, Herschel-Bulkley, Michaels and Bolger models. The power law flow behavior index values were in the range of 0.14 to 0.19. Presence of measurable yield stress indicated Bingham model of the pulps. Storage of pulps for 30 weeks had negligible influence on flow behavior index values. The consistency index and yield stress values decreased with extending storage from 0 to 30 weeks. The Michaels and Bolger model distinctly described the non-Newtonian nature of cold- and hot-break pulps as well as different behavior of the pink guava pulps. The structure shear resistance values for hot-break pulps at zero shear rate were considerably higher than those of the cold-break, indicating their high pseudoplasticity.