Assessment of the profile of fungal defense-related metabolites in tomatoes during ripening by classical and NMR techniques

This study assessed the profile of defense-related metabolites in tomatoes during ripening by classical and NMR techniques to infer their susceptibility to fungal damage at ripening. Tomatoes of the Khaki variety at different ripening stages were standardized regarding their ripeness indicators (color and relation sugar/acid). It was determined pectin content, phenolic profile and activity of enzymes invertase, polygalacturonase, peroxidase, polyphenol oxidase, catalase and phenylalanine-ammonia-lyase. Both 1H and 13C NMR spectra were used for focusing on metabolites responsible for the defense mechanism, phenolic compounds and organic acids, reinforcing the results from conventional determination. The main change on the defense-related components at ripening stages were the phenolic profile, organic acid and activity of enzymes. The activity of enzymes related to the defense of the fruit decreased during the change from the turning stage to the ripe stage, suggesting that this is a critical point of management to prevent fungal post-harvest damage in tomatoes. The NMR technique was very promising to screening fruit metabolite profiles that were at different stages because it needs little sample preparation, releases fewer residues, results fast and it is less susceptible to experimental errors.