Postharvest cold storage in zucchini fruit extends the commercial life but causes the appearance of
chilling injury (CI), characterized by the development of pits and damaged areas at the surface of the fruit.
This physiological disorder has been related to alterations of the cell wall metabolism in several fruit. We
have analyzed the relationship between the development of CI and the changes that take place at the cell
wall due to cold storage in zucchini fruit, as well as the effect of a preconditioning treatment on these
changes. Microscopical observations have shown that the surface depressions detected in chilling injured
fruit were caused by cell death and cell collapse. Low temperature induced the solubilization of the more
soluble pectins, as evidenced by the highest levels of neutral sugars and uronic acids found in control fruit
after the cold storage in water-soluble fraction (WSF) and CDTA-soluble fraction (CSF). The results
obtained in Na2CO3-soluble fraction (NSF) for both parameters was opposite; higher levels were detected
in preconditioned fruit and lower in more damaged fruit. The same behaviour was found in the base
soluble hemicelluloses, 1 M KOH- and 4 M KOH-soluble fractions (1KSF and 4KSF), and in the insoluble
cellulose content. Zucchini fruit stored at low temperature showed an increase of the enzymatic activities
pectin methylesterase (PME), polygalacturonase (PG), and cellulase (CEL), and an accumulation of mRNA
corresponding to a expansin (EXP) gene. Preconditioned fruit showed the lowest levels of these
enzymatic activities. Microscopic analysis of CI fruit correlated with the biochemical changes observed in
cell wall. Lignin content was higher in control than preconditioned fruit, suggesting a possible role of the
lignification process in CI development in zucchini.