Treatments with acetic acid followed by curing reduce postharvest decay on Citrus fruit.

Citrus fruit are susceptible to many postharvest diseases and disorders, but Penicillium digitatum and Penicillium italicum are the most common and serious pathogens during storage and marketing. The continuous employ in packing houses of synthetic fungicides such as imazalil (IMZ) or thiabendazote for the control of these pathogens is promoting the selection of resistant biotypes. These considerations together with an increased attention for human health and the environment have multiplied the studies on new ecological technologies. In recent years researchers studies focused on alternatives to the chemical control of post-harvest decay, such as the utilization of GRAS compounds as well as physical methods. In the present study is reported the sequential use of acetic acid (AAC) followed by curing. The lemon variety "Verna" and the orange variety "Jaffa", naturally inoculated, were treated with vapours of AAC performed at three different concentration (15, 25 and 50 microL/L) for 15 minutes, after an incubation period of 24 hours at 27 degrees C and 90% relative humidity (RH). After treatments fruits were cured at 36 degrees C for 36 hours with 90% RH and subsequently stored at 8 degrees C and 90% of RH for eight weeks. Both citrus varieties were also treated with IMZ at a concentration of 200 mL/HL. At the end of the experiment decay and weight loss were evaluated. After 8 weeks of storage, in the lemon variety, the lowest percentage of infected wounds was 1.5% for both the fruit treated with IMZ or with AAC at 25 microL/L. Fruit treated with 15 mciroL/L or untreated (control) showed similar results with 13.6% and 16.6% of rotted fruit respectively. Different results were obtained with the orange variety, in this case the synthetic fungicide was the most effective at the end of the storage period, with 18.0% of decay. AAC treatments were not a successful as on lemons, the best result was achieved even in this case with AAC performed at 25 pL/L, but with 39.9% of decay. In both species the weight loss was not affected by the treatments. These results show that a good control of postharvest decay could be achieved, on lemon fruit, by combining the effect of a GRAS compound such as AAC with curing. Conversely the results obtained, by applying this control method to the orange variety were not so promising. Further researches are needed to shed light on the different behaviour between the two species.

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 microl/L) of AAC vapors, for 15 minutes, single berries inoculated with B. cinerea. After treatments fruit was incubated at 20 degrees C for one week. The in vivo experiment took place by using the most promising AAC concentrations (50, 75 and 100 microl/L) followed by eight weeks of storage at 5 degrees C and 95% of relative humidity (RH) and four days at 20 degrees 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 microl/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 microl/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 microl/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.