The role of characteristic times in rheological description of structure forming food additives Original Research Article

The work is focused on the interpretation of flow curves obtained at two different temperatures for water solutions of xanthan and guar gum, and pastes of oxidized corn starch and starch phosphate. Based on exponential state equations for shear thinning and shear thickening systems characteristic times distributions were estimated using Tikhonov regularization method. Values of time constants and their intensities were strongly associated with the composition of the examined mixtures. Food thickeners such as GG or XG form solutions of very high viscosity. Characteristic times determined from De Kee equation take large values (0.1–1 s). This could be connected with a predominance of viscous behavior during shear. Starch pastes with GG or XG show very complex rheological behavior resulting from synergistic effects. This is reflected in the form of distributions of time constants, which have two peaks. One of them is specific to the non-starch hydrocolloid and corresponds to the characteristic time of approximately 1 s. Global maximum is located at the time of 0.001 s and is associated with the presence of starch and its gel structure. The differences in rheological characteristic times for various structure forming agents reflect their technological functions.