No abstract

The applicability of a thermal treatment was compared with modified-atmosphere (MA) storage in relation to chilling injury (CI) and polyamines evolution in eggplants. Fruits underwent physiological disorders at 3 degrees C, evidenced by the appearance of surface injuries at the third day of storage, and, after moving the fruits to 20 degrees C, by increased respiratory activity and more intense ethylene production. Storage of fruits in sealed low-density polyethylene bags and a previous treatment with heated air (1 h at 35 degrees C) were both effective in retarding chilling injury, though the former was better. Two free polyamines were found in cv. Black Nite: putrescine, in greater proportion, and spermidine. Putrescine increased in control (untreated) fruits stored at 3 degrees C in parallel with the external appearance of chilling injury, whereas this increase was either not exhibited or retarded in treated or MA stored fruits. Spermidine did not change in control fruits at 3 degrees C, remaining almost constant over the whole storage period, whereas in heat- and MAP-treated fruits spermidine levels exhibited a decrease.

Molecular oxygen electroreduction at both Pt and Au electrodes in acetonitrile solutions was studied by RDE and cyclic voltammetry techniques. Hydrogen peroxide was detected as the main reaction product on Pt as well as on Au electrodes. Molecular oxygen dissociative adsorption is inhibited by the organic solvent which produces a leveling effect of metal catalytic properties. Results obtained by cyclic voltammetry allowed the interpretation of the electrochemical process as a reversible single electron transfer to give O2− , followed by the disproportionation of superoxide ion that in the presence of residual water could account for hydrogen peroxide formation. The disproportionation constant was evaluated, its value being of the order of 105 M sec−1. These results were further confirmed by the experiments performed at the RDE.