Effect of some enzymes treatment on rheological behavior of strawberry juice and its concentrates
2005
Bahlol, Hammam E.
Strawberry juice (7.5 °Brix) was prepared and treated with (Pectinex. M and Rohament MAX) enzymes at different dosages (0. 300 and 600 ppm) after that the strawberry juice preparations were concentrated to 2, 3 and 4 folds. Rheological properties of these preparations were studied at a temperature range 5-80C and shear rate range 0.3 to 100 s. 1 by using Brookfield Digital Viscometer Model DV-11+. The Bingham, Casson, IPC Paste and Power Law rheological models were applied to describe the rheological properties of all preparations. These properties are key parameters required to solve food industry problems in numerous areas: quality control, evaluation of consumer acceptance or texture (including physicochemical changes which occur during processing and storage). The results indicated that strawberry juice preparations behave as nonNewtonian fluids (pseudoplas tic) and have a definite yield stress. The Bingham and Casson plastic viscosity and yield stress, 10 RPM viscosity, consistency index and flow index, decreased with increasing enzyme dosage. Rohament MAX enzyme was more effective in reducing viscosity and rheological parameters than Pectinex. M enzyme at different concentrations and temperatures. The effect of temperature on the viscosity can be described by means of an Arrhenius-type equation. The activation energy for viscous flow depends on the total soluble solids. The (Bingham and Casson plastic viscosity and yield stress, 10 RPM viscosity, consistency index and flow index) decrease with increase of temperature. Sensory evaluation for all preparations were carried out.
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