In recent years, heat treatment has been used to prevent the development of chilling injury in fruits and vegetables. The acquired tolerance to chilling seen in treated fruit is related to the accumulation of heat shock proteins (HSPs). The positive effect of heat treatment has generally been verified for only a narrow range of treatment intensities and more reliable methods of determining optimal conditions are therefore needed. In this regard, quantitation of HSPs would seem to be an interesting tool for monitoring purposes. As a step toward the development of analytical methodology, the objective of this study was the isolation and characterization of relevant HSPs from plant tissues. Tomato fruits were exposed to a temperature of 38 degrees C for 0, 3, 20 and 27 h, and protein extracts from pericarp were analysed using SDS/PAGE. Analysis revealed the appearance of an intense 21 kDa protein band in treated samples. IEF of this band showed the presence of four major proteins (HSPC1, HSPC2, HSPC3 and HSPC4) with similar pI values. A monospecific polyclonal antiserum was raised in rabbits against purified HSPC1 protein, which cross-reacted with other small heat shock proteins. The major proteins were characterized by MS/MS analysis of tryptic peptides, all having blocked N-termini. The antiserum obtained proved suitable for detecting increased amounts of small heat shock proteins in tomatoes and grapefruits subjected to heat treatment for 24 and 48 h; these treatments were successful in preventing the development of chilling injury symptoms during cold storage. Our data are valuable for the future development of analytical methods to evaluate the optimal protection induced by heat treatment in different fruits.