Complexation of Imazalil with Beta-Cyclodextrin, Residue Uptake, Persistance, and Activity against Penicillium Decay in Citrus Fruit Following Postharvest Dip Treatments

A method for the inclusion of imazalil (IMZ) in the ‚Beta-cyclodextrin (Beta‚CD), structural characterization of the inclusion complex and its antifungal activity against Penicillium digitatumand P. italicumassessed by in vitro and in vivo tests are reported. According to the starting stoichiometry of BetaCD with respect to IMZ, an equimolar ratio ‚Beta-cyclodextrin-IMZ (BetaCD-IMZ) was detected by 1H NMR. In vitro assays showed that the freshly prepared BetaCD-IMZ was as effective as IMZ, although 1- and 4-day-old BetaCD-IMZ mixtures were more effective. Studies on Star Ruby grapefruit showed no significant differences in residue uptake between treatments with an IMZ commercially available fungicide (Deccozil) or BetaCD-IMZ when equal active ingredient (a.i.) concentrations (250 mg/L) and dip temperatures (20 or 50 °C) were used. By contrast, treatments of Tarocco oranges and Di Massa lemons with 250 mg/L BetaCD-IMZ at 50 °C produced significant differences in residue uptake in comparison with 250 mg/L Deccozil treatments at 50 °C. The a.i. degradation rate in grapefruit during postquarantine and simulated marketing period (SMP) at 20 °C was not affected by the type of formulation used, whether at 20 or 50 °C. Conversely, IMZ in oranges and lemons had greater persistence when applied at 50 °C. All fungicide treatments showed a comparable efficacy against decay in grapefruit and oranges, whereas treatment in lemons at 250 mg/L a.i. of heated fungicides had higher suppressive effects against decay than unheated chemicals having equal a.i. concentrations and comparable activity at 1200 mg/L IMZ at 20 °C.