The specific heat of isolated tomato fruit cuticles and their corresponding cutins have been measured by first time for the physiological temperature in the range of 0-55degreesC. Variation of specific heat of the different isolates during fruit growth have been also measured. Isolated cuticles and cutin from young tomato fruits presented a clear glass transition temperature around 23degreesC. Water sorption on cutin samples shifted the glass transition temperature to 16.3degreesC indicating a clear plasticization of the biopolymer. The presence of these second-order transitions in these lipophilic plant material that act as a molecular barrier between the atmosphere and the plant cell, determine the mechanical and theological properties of this biological barrier modulating the mass transfer between the environment ant the plant cell. (C) 2003 Elsevier B.V. All rights reserved.