Flow Pattern of the Dispersed System of Tobacco and Water during Extruding. IVInfluence of Water Content on the Apparent Viscosity of Tobacco-Water Systems and Its Interpretation in Terms of Their Pressure Transmission Characteristics

摘要

In spite of little difference in chemical compositions between the residues on extraction of the flue-cured tobacco (Bright Yellow) and that of the air-cured tobacco (Matsukawa), an appreciable difference in apparent viscosity ηa appeared between dispersed systems of these residues in water. To clarify the reason of the difference, the pressure transmission characteristics of the systems were examined in a closed cylinder apparatus. The following results were obtained.For the systems of the residues in water, the rate of transmitted pressure increased with the increase of water content of the systems, and the inclination of the rates changed remarkably at some water content ψ′critical. Up to the contens ψ′critical, water was bound tightly to the particles as adsorptive water, and did not behave as dispersion medium. At higher water contents, a layer of water was formed around the particle and its thickness d was evaluated by _??_.Here A(m2/g) is the specific surface area of the residue and ρ (g/cm3) is the density of the medium. The apparent viscosities ηa for the two residues having different specific surface areas gave a single line in the plot of log ηa against d. For the systems of the Matsukawa residue in sugar solution or KNO3 solution, the value of ψ′critical changed with the concentration of solutions. Apparently, the results suggested that the thickness of the adsorptive film decreased with the increase of the concentration. The log ηa vs. d plot obtained for the systems of sugar solutions gave a curve essentially similar to that for the water systems.