Proceedings of the 2nd International Symposium on Food Rheology and Structure pages:25-33
2nd International Symposium on Food Rheology and Structure edition:2 location:Zurich date:13-16 March 2000
In addition to rheo-mechanical shear and oscillation measurements, recent years have also seen the parallel determination of rheo-optical material functions, such as flow birefringence and flow dichroism, used in order to investigate macroscopic viscoelastic flow behaviour at a molecular level. Apart from determining these moduli, which are proportional to rheo-mechanical parameters, it was also possible to determine the orientation of polymer segments and aggregated structures. In particular, it became possible to explain aggregation behaviour during the sol-gel transition and during temperature-induced phase separation on a molecular level. Investigations centred mainly on polysaccharides relevant to applications in the food industry. In addition to native polysaccharides (maize starch, waxy maize starch, waxy rice starch, potato starch, locust bean gum, guar, carrageenan, -glucan) and mixtures of these, investigations also included chemically modified celluloses (CMC, HPMC, HPC) and fermentation polymers (xanthan, schizophyllan). Particular consideration was given here to the dependence of the viscoelastic properties on concentration, molar mass, molar mass distribution, degree of substitution, solvent quality and temperature. The overriding aim was to establish structure-property relationships by correlating the rheo-mechanical and rheo-optical material functions with data from polymer analysis.