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 used to study the flow behavior of a 11 Brix tomato puree at several temperatures in the range: 76 to 120C. The activation energy of flow of the tomato puree, based on apparent viscosity at 50 s−1, was: 9.4 kJ mol−1. The apparent viscosity (η) versus temperature profiles of a 4.0% waxy rice (WR) starch dispersion were determined during continuous heating from 30 to 110C at six shear rates in the shear range: 114 to 644 s−1; beginning at about 95C, significant increase in ηa was observed at 114 and 160 s−1. The said profiles collapsed to a single curve when ηa values were converted to reduced viscosity, values of η of the starch dispersion were lower than those of η* at about the same shear rates, γ=5.7 s−1 and ω=6.3 rad s−1.