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Bull. Spec. CORESTA Congress, Jerez de la Frontera, 1992, p. 99, ST25, ISSN.0525-6240

Rheology of homogenized tobacco

DE VOS J.
Tamag Basle Ltd., Birsfelden, Switzerland.
We offer a process for the production of homogenized tobacco sheet from offals such as stems, scraps and dust. In preparation for the sheet forming step, the ground tobacco waste is compounded with an aqueous binder dispersion to an extrudable dough; the binders are polysaccharides, used in stoichiometric equivalence with the tobacco stem content. Apart from Van Der Waals-London forces, bonds are mainly a result of hydrogen-bonding mechanisms; in the design of the compounding step sufficient residence time must be allowed for those reactions to run to completion. The present paper reviews the use of creep strain curves for the determination of compounding time requirements. The general shape of the curves conforms to the Burgers mechanical model. Properly formulated sheet-making doughs are shear-thinning, thixotropic compounds with a minimum yield stress. Flow curves of such compounds include both viscous and elastic components which can be determined from the dynamic response of a 2nd order system to sine-wave excitation. Experimental data on complex dynamic viscosity in oscillatory shear flow will be presented, followed by a review of their use in process design calculations. An additional benefit of the technique is that measurement of the complex dynamic viscosity also facilitates selection of binder formulations for good product filling power.