Effect of moisture content on selected physicochemical properties of two commercial hen egg white powders

After short-term storage at 23 °C, selected physicochemical properties of two hen egg white powders (with and without hydrolysis) were studied. Overall, the effect of moisture content on physicochemical properties of Hydrolysed Egg White powder (HEW) was more severe than those of Dried Egg White powder (DEW). The denaturation temperature (T_d) and its enthalpy change (ΔH_d) of ovalbumin in DEW followed an exponential model, as well as the T_d of HEW. The Gordon-Taylor equation modelled well the glass transition temperatures (T_g) of HEW and DEW. The Guggenheim-Anderson-de Boer (GAB) model fitted well to the type II moisture sorption isotherm. At the critical moisture content (12.0%, dry basis), compared with DEW, the colour of HEW began to darken dramatically and its hardness started to change significantly. These changes were closely related to the inherent characteristics of the two products. The mechanisms relevant to these physicochemical changes were discussed.