Acetic acid treatments to keep postharvest quality of "Regina" and "Taloppo" table grapes

The most important postharvest pathogen for table grape is Botrytis cinerea (gray mold), which cause a rapid deterioration of fruit. An effective control of the disease during storage is difficult and remains an unsolved problem since no pesticide treatments are allowed by European legislation. GRAS compounds, employed with no restriction as preservatives in Europe and North America, are possible candidates to fulfil this gap. The aim of this work is to study the efficacy of Acetic Acid (AAC), used as postharvest treatment to control Botrytis cinerea on "Regina" and "Taloppo" table grapes, by Laboratory and storage tests. The activity of this compound was first assessed with laboratory tests, treating at different concentrations (0, 5, 10, 20, 50, 75 and 100 ?/L) of AAC vapors, for 15 minutes, single berries inoculated with B. cinerea. After treatments fruit was incubated at 20 °C for one week. The in vivo experiment took place by using the most promising AAC concentrations (50, 75 and 100 ?/L) followed by eight weeks of storage at 5 °C and 95% of relative humidity (RH) and four days at 20 °C and 85% RH (simulated shelf-life conditions). At the end of the in vivo experiment decay, weight loss and visual assessment were evaluated. Almost all treatments, after eight weeks of storage, reduced the incidence of gray mould. The best results were achieved by using 50 ppm of AAC, gaining a reduction of decay, compared to untreated "Taloppo" and "Regina" grapes of 61.0% and 41.4%, respectively. Following the simulated shelf-life period differences between treated and untreated (control) became no significant for "Taloppo" grape, while the lowest decay percentage was reached with 50 ?/L of AAC for "Regina" grape (52% of reduction if compared to control). Regarding fruit weight loss all treatments did not affect significantly this parameter that ranged between 8.2% and 11.5% after eight weeks of storage and 13.5% and 18.2% after shelf-life. At the end of storage the highest visual score was attributed to fruit treated with 50 ?/L of AAC evidencing a clear better keeping quality. During this period slight treatment damages were observed on berries following application of AAC at 75 and 100 ?/L. The reported results obtained with these experiments showed that Acetic Acid could be a promising compound to be used as alternative to SO2 in keeping grapes quality and controlling decay during storage.