RHEOLOGICAL CHARACTERIZATION OF PEACH PUREES

Abstract

ABSTRACT In this work, two commercial peach purees (21 and 11.9°Brix) industrially obtained have been studied at several temperatures involved in industrial processes. Viscoelastic functions were that of a weak gel, and decreased with temperature and increased with concentration. Rheograms were obtained in order to determine the yield stress, which is related to stability against settling during storage. Herschel–Bulkley equation was used to determine the consistency index and the flow index. Thixotropy was quantified by means of one empirical equation (Weltmann model) and two theoretical equations (Figoni–Shoemaker and Tiu–Boger models), which describe the first‐ and second‐order kinetic process of structure breakdown. Both peach purees show thixotropy under nonsteady conditions. The broken‐down structure increased with the applied shear rate and, practically, decreased as the temperature was increased for both peach purees. The breakdown kinetic constants decreased as the shear rate was increased for both theoretical equations following a power law dependency. PRACTICAL APPLICATIONS It is necessary to know the thixotropic behavior of peach purees, since knowledge of the rheological properties is very important in order to improve the design, manipulation and calculation of all those unit operations during the process (i.e., agitation and filtration) and design equipment (i.e., pump systems and pipe sizing), mainly those based on heat and quantum transfer.