RHEOLOGICAL BEHAVIOR OF PROCESSED MUSTARD .2. STORAGE EFFECTS

Samples of processed yellow mustard with three different particle size distributions (slightly-coarse, standard, and fine) were prepared according to a standard formulation and pilot-plant replication of the commercial methodology and stored for 3 months at 5-degrees-C, 25-degrees-C, and 45-degrees-C. After 3-month storage at 45-degrees-C, all samples showed visible liquid separation (syneresis) and aggregation of colloidal particles, as indicated by increase in d(pop) and decrease in % colloids. The fine milled samples exhibited syneresis and an increase in d(pop) after 3-month storage even at 25-degrees-C. The bimodal distribution did not show significant changes as a result of aggregation. In general, increase in d(pop) increased apparent viscosity (eta-ap), flow behavior index (n) from the Herschel-Bulkely model, and exponent n" from the loss modulus (G") power law equation. As d(pop) increased, Bingham yield stress sigma-o), plastic apparent viscosity (eta-p), shear stress constant (A) from the Weltman stress decay model, yield stress (sigma-o) and consistency index (m) from the Herschel-Bulkley model, exponent n' from the storage modulus (G') power law equation, and minimum values of loss tangent (tan delta) decreased. In heterodisperse semi-solid foods such as processed mustard, the particle size distribution influences the structure (i.e., packing) and the rheological behavior. Therefore, time and temperature dependent instabilities such as syneresis may be minimized by controlling particle size distribution during processing.