Rheological properties of commercial mustards

Abstract

Seven commercial mustards, made by different manufacturers, were studied to examine their physicochemical and rheological properties and to establish relationships between those properties. Physicochemical analysis revealed distinct differences between the mustards in the dry matter and extract contents and smaller differences in the protein, fat and ash levels. Two of the investigated mustards did not satisfy the requirements of the relevant Polish standard regarding dry matter content. Rheological studies included determination of the following: (a) flow curves with a controlled shear rate or shear stress, (b) curves showing the time and temperature dependence of apparent viscosity, and (c) mechanical spectra. Apparent viscosity and complex viscosity were correlated using the generalised Cox–Merz rule. The rheological investigations confirmed that mustard is a pseudoplastic fluid exhibiting a yield stress, thixotropy and viscoelastic (with dominant elastic) properties. Statistical analysis of the results showed significant linear correlations between the dry matter, fat, protein and ash contents of mustards and some parameters of rheological models.