Thermodynamic properties at low temperatures were investigated for alpha,alpha-trehalose dihydrate and alpha,beta-trehalose monohydrate. The heat capacities were measured using an adiabatic calorimeter at temperatures between 13 K and 300 K. The heat capacity data were expressed as a function of temperature, T, by a polynominal of forth to sixth order, with which thermodynamic functions, enthalpy, entropy, and Gibbs free energy, were determined. (c) 2006 Elsevier Ltd. All rights reserved.