Calculation of water activity in electrolytic solutions using the Electrolattice and Q-Electrolattice equations of state

Abstract

Water activity directly influences the deterioration, texture, pigmentation, and preservation of nutrients in food. This property quantifies the availability of water for the enzymatic, chemical, or microbiological activity that defines the shelf life of food. In this way, the food industry needs to measure, predict, and control this property. In this context, the present work aims to evaluate the performance of the Electrolattice and Q-Electrolattice equations of state in predicting and correlating the water activity of solutions containing electrolytes. Parameters available in the literature were used to compare the performance of the Electrolattice and Q-Electrolattice equations in predicting the water activity (in binary, ternary, and quaternary solutions of salts). The Q-Electrolattice model presented better performance than the Electrolattice equation, with a relative mean deviation (RMD) of 1.95%, 0.14%, and 0.06% for binary, ternary, and quaternary aqueous electrolytic solutions, respectively. Then, the Q-Electrolattice equation was used to correlate experimental data of systems containing water + NaCl + sugar (fructose, sucrose, glucose, and xylose) at 25°C and water + sugar (fructose, sucrose, glucose, and xylose) at 35°C in aqueous solutions of salts and sugar. The general weighted average of the RMD% was equal to 0.29%. Finally, the procedure was validated with solutions containing water, NaCl, and sugar (fructose, sucrose, glucose, and xylose) at 35°C, a condition that was not used in the parameter fitting process. The overall weighted average of the RMD for predicting the water activity of water + NaCl + sugar solutions at 35°C using the Q-Electrolattice equation was 0.57%, thus validating the parameters estimated in this work. The results obtained in this study showed the feasibility of using the Q-Electrolattice equation to predict water activity in aqueous solutions of salts and sugars used as a basis for the osmotic drying of food.