Effect of concentration on the rheology and serum separation of tomato suspensions

The (o)Brix value of the tomato concentrate, from which tomato suspensions were prepared, was shown to have a large effect on the resulting apparent viscosity and storage modulus. The apparent viscosity of a tomato suspension prepared from a 30 (o)Brix tomato concentrate was only 35% of that of a suspension prepared from a 4.9 (o)Brix juice, both standardized on the same water unextractable solids (WUS) (0.65%) and total tomato solids (TS) level. After homogenizing the difference in apparent viscosity was only about 10-15%. A similar trend was found for the dynamic moduli. The decrease in rheological parameters of the nonhomogenized suspensions is probably partly related to the decrease in diameter of the tomato particles due to the concentration process. Moreover, microscopic fracture of the cellulosic, microfibrillar network of the cell wall plays a part. Serum separation of diluted nonhomogenized tomato suspensions was higher if made from a concentrate that was concentrated to a higher (o)Brix value. This phenomenon is discussed in terms of variations in uniaxial compression of the network in the diluted tomato suspensions caused by gravitational force.