Volume 17, Issue 2

A specific twin channel slit die was used to measure in-line the viscous behaviour of an extruded wheat starch. This allows to put in evidence the influences of temperature, water content and specific mechanical energy (SME). The proposed rheological law permits to satisfactorily predict the viscosity of a wheat starch for any processing condition. Original results are presented for the behaviour of cationic starches obtained by reactive extrusion.

We describe methodology of laser Doppler forced vibrology (LDFV) applied to texture assessment of soft agricultural products. The method is applied to a melon. The lowest frequency resonant peak (mode M0 ) is used for corrections of the whole amplitude frequency plot expressed in relation to the forcing deformation level. The main differences between vibrology in vertical and horizontal laser positions are described. Missing and/or degeneration of some modes in the laser horizontal position are explained. Peak analysis of the results obtained reveals the parameters connected with information on internal damping, i.e. internal viscosity. Modulus of elasticity is calculated either from the peak frequency of the M1 mode or by a new method from the M0 peak frequency. The modulus of elasticity of the latter method is nearly one order higher and is more variable than the former probably because the M0 mode is related to physical properties of the surface of the melon in contact with the vibrating table. Fine structure of the skin can lead to possible degenerated forms with more sub-peaks.

Models of kinetic theory provide a coarse-grained description of molecular configurations wherein atomistic processes are ignored. The Fokker-Planck equation related to the kinetic theory descriptions must be solved for the distribution function in both physical and configuration spaces. When the model involves high dimensional spaces (including physical and conformation spaces and time) standard discretization techniques fail due to excessive computation requirements. In this paper, we revisit some model reduction techniques recently proposed to circumvent those difficulties, exploring other new application areas related to entangled polymer models as well as the use of such reduced models for treating complex flows in which the distribution function involves both the physical and the conformation coordinates.