Um reoviscosímetro de queda de esferas de baixo custo para fluidos alimentares.

Abstract

The falling ball viscosimeter (Hoppler) was modified to measure the rheological properties of non-Newtonian food fluids. The theory that formed the basis in developing this rheoviscosimeter was the analysis of slow falling of rigid spheres in the vicinity of non-Newtonian fluids. An electromagnetic device with automatic chronometry has permited the determination of the corresponding shear stress and the shear rate through the terminal velocity measurements, including non transparent fluids. The falling ball rheoviscosimeter demonstrated precision when tested with a Newtonian product (glycerol) and gave flow constants not significantly different from those obtained using rotoviscosimeters for the evaluation of a non-Newtonian product (carrageenan). The rheological parameters (K, n) of carageenan, in this work, demonstrated agreement when compared with results obtained with different rheoviscosimeters. Although the modified Hoppler viscosimeter as reported here does not encompass as wide a range of shear rates as some of the more expensive instruments, its range is sufficiently large to include most food fluids in respect to the stimulations associated with  the sensory evaluation of viscosity.