Zucchini fruits were subjected to 2.5 or 10 degreesC for 16 d, followed by transfer to 20 degreesC for 24 h in order to evaluate the relationship between ripening pattern. measured as CO2 evolution and ethylene (C2H4) production, and metabolic heat production (q). Chilling injury (CI) visible symptoms were evident after 8 d at 2.5degreesC, but none were recorded on fruits kept at 10degreesC. In fruits held at 10degreesC, q, C2H4 production. and CO2 evolution diminished in the course of 16d, whereas in those at 2.5degreesC CO2 evolution showed an early burst peaking at 8 d. Both C2H4 production and q also showed a burst at 2.5degreesC but they started at 4 and 8 d, respectively, and peaked at 122 d. The results showed that irreversibility of chilling injury in zucchini could occur long before the appearance of visible symptoms. although the metabolic activity accompanying the irreversibility process was not noticeable by isothermal calorimetry. (C) 2003 Elsevier Inc. All rights reserved.