High temperature rheology of tomato puree and starch dispersion with a direct-drive viscometer

A direct-drive concentric cylinder viscometer in a pressure chamber was use d to study the flow behavior of a 11 Brix tomato puree at several temperatu res in the range: 76 to 120C. The activation energy of flow of the tomato p uree, based on apparent viscosity at 50 s(-1), was: 9.4 kJ mol(-1). The app arent viscosity (eta(a)) versus temperature profiles of a 4.0% wary rice (W R) starch dispersion were determined during continuous heating from 30 to 1 10C at six shear rates in the shear range: 114 to 644 s(-1); beginning at a bout 95C, significant increase in eta(a), was observed at 114 and 160 s(-1) . The said profiles collapsed to a single curve when eta(a) values were con verted to reduced viscosity, eta(aR) = eta(a)((gamma) over dot/(gamma) over dot(r)). Values of eta(a) of the starch dispersion were lower than those o f eta* at about the same shear rates, (gamma) over dot = 5.7 s(-1) and omeg a = 6.3 rad s(-1).