Variable hydration of small carbohydrates for predicting equilibrium properties in diluted and concentrated solutions

A physical–chemical model is proposed to describe the equilibrium properties of binary and multicomponent water–carbohydrate mixtures.The chemical part of the model accounts for the hydration equilibrium of carbohydrate with the formation of carbohydrate n-water molecules in a single stage process; n, the hydration number, and K, the hydration equilibrium constant, are the two independent parameters in this part.The physical part of the model is the UNIFAC group-contribution model as modified by Larsen et al. (I.E.C. Research, 26 (1987) 2274–2286). The original functional groups and the structural and interaction parameter values are maintained and introducing new groups such as pyranose rings, furanose rings and osidic bonds was not necessary.The model is compared to experimental data including water activity, osmotic coefficients, activity coefficients, freezing and boiling point temperatures and solubility for binary systems containing xylose, glucose, mannose, galactose, fructose, sucrose, maltose, lactose and trehalose and for food products containing sugars.