Rheological methods to analyse the thermal aggregation of calcium enriched milks

Abstract

The colloidal state of calcium enriched milks during heating and its microstructures were analysed through interpretation of rheometric data with the Brownian aggregation theory, which can be considered as complementary to the methods currently used. Viscosity was measured at 100 s−1 through temperature and time sweeps. It was observed that from 25 to 60C, viscosity slowly decreased as temperature increased; above 60C, viscosity sharply increased at different temperatures depending on the amount of CaCl2. From time sweeps, the aggregation of casein micelles was described through the Smoluchowski theory. The addition of CaCl2 at concentrations of 20 to 30 mmol kg−1 decreased the stability factor 5 to 6 orders of magnitude compared with non-enriched milk. Values of the fractal dimension indicated that aggregation yields disordered aggregates occluding high amounts of solvent. The methodology described may help to analyse colloidal stability and structures when different calcium salts are used for enrichment.