RHEOLOGY OF POMEGRANATE JUICE EXTRACTS AND CONCENTRATES

The rheology of pomegranate juice extracts and concentrates of the two varieties Khob Al-jamil and Mellasy has been studied at a wide range of temperatures (5-65C), concentra ons (15-65Brix) and shear rate (l0-500 s-1), using a Brookfield cone and plate version rheometer. The results indicated that fresh pomegranate juice extracts (15 and 17Brix) behaved as Newtonian fluids while the other concentrates (25-65Brix) are nonNewton exhibiting a pseudoplastic (shear-thinning) behavior. The effect of temperature on the apparent viscosity of concentrates followed the Arrhenius-type equation and the activation energy for the concentrates ranged from 4361.3 to 36737.9, 5140.1 to 40003.6 and 5918.9 to 43268.6 kJ/kmole for the Khob Aljamil concentrates, and from 6511.9 to 28890.3, 7008.9 to 32284.1 and 7505.8 to 35678.7 kJ/kmole for the Mellasy concentrates over the concentra on range of 25 to 65Brix and at the shear rates 50, 100 and 200 s-1, respectively. The effect of concentration on values of the apparent viscosity evaluated at shear rate of 100 s-1 for various pomegranate concentrates was also examined, and was described by power-law and exponential equations. The values of r2 revealed the adequacy of the exponential-type equation than the power-type equation. Finally, four equations that describe the combined effect of concentration, temperature and shear rate on the apparent viscosity of various pomegranate concentrates were developed