EFFECT OF THE HOMOGENIZATION PROCESS ON THE RHEOLOGICAL PROPERTIES OF FOOD EMULSIONS

摘要

The aim of this study was to assess changes in rheological characteristics and droplet size distribution in emulsions studied under the influence of the one- and two-stage homogenization processes, carried out at a pressure higher than in standard industry practice. The material consisted of food emulsions of the o/w type, with an oil phase content of 9%, 12%, and 18% of mass, in a 20% solution of milk protein concentrate. The one- and two-stage homogenization processes were carried out using a ?Panda" laboratory homogenizer from GEA Niro-Soavi at the pressure of 30 MPa and 30/6 MPa at 45,0 + 0,5°C. The degree of fat despersion was determined with the microscopic method, by using computer image analysis. The flow curves of the emulsions tested weredetermined using the rheometer of the Rheostressl type with a concentric cylinder system Rotor 234 DIN 53019, at an increasing shear rate (y) ranging from 0,04 to 700 s"1. Changes in shear stress versus shear rate value O = f{y)were described using theOstwald de Waele power-law model. It was found that subjecting food emulsions to one- and two-stage homogenization pressure resulted in changes in the rheological parameters of flow curves. Droplet size depended on the percentage of oil in the emulsion and homogenization conditions. The homogenization process was followed by a significant decline of the consistency coefficient and a slight increase in the flow rate. These changes prove the effect of the homogenization process on the structure of emulsions.