The thermophysical properties of guava (Psidium guajava L.) juice of the Thai seedless variety at medium maturity as affected by temperature and concentration were studied. The thermophysical properties were determined at concentrations between 10 and 40 degreesBrix and temperatures between 30 and 80 degreesC. The apparent viscosity (mu) and density (rho) decreased with increase in temperature, while the specific heat capacity (C-ps) increased as temperature increased. However, the thermal conductivity (k) was not influenced by temperature. The apparent viscosity (mu), and density (rho) increased as concentration increased. (C) 2004 Elsevier Ltd. All rights reserved.