Sorption isothermes and physicochemical characterization of dried milk products

Abstract

The aim of this study was to determine the composition, establish the isotherms at 25 º C and apply the BET model for instant whole milk powder (LPI), instant skim milk powder (SMP), half skim milk powder (LPSD), pre-crystallized whole whey by primary nucleation (SPNP), pre-crystallized whole whey by adding 0.05% w / w of lactose (SP0, 05) and pre-crystallized whole whey by adding 0.1% w / w lactose (SP0,1). The Brunauer, Emmett and Teller (BET) model was utilized for analysis of the experimental data. Isotherms of the dried milk products evaluated were fitted to the BET model and the moisture contents were higher than those calculated for the monolayer. Water mass in the monolayer calculated by the BET model presented a statistically significant negative correlation (p=0.026) with the fat concentrations. The difference between enthalpy of adsorption in the monolayer and enthalpy of water condensation between water molecules in the monolayer and in the pure solvent presented statistically significant positive correlations with the concentrations of lactose (p=0.001) and negative correlations with moisture content (p=0.005).