Postharvest Conservation of 'BRS Nubia' Hybrid Table Grape Subjected to Field Ultra-Fast SO2-Generating Pads before Packaging

The gray mold caused by Botrytis cinerea is the main concern for the postharvest conservation of table grapes worldwide, and the use of sulfur dioxide (SO2) is the most common practice for its control. The aim of this work was to assess the postharvest conservation of the hybrid table grape 'BRS Nubia' by using a new technology known as a field ultra-fast SO2-generating pad before packaging the grapes. The fruits were harvested in the 2021 season from a commercial vineyard located at Marialva, Parana, Brazil. The experiment was conducted in a completely randomized design, with 4 treatments and 4 replications, and each plot consisted of 10 bunches. The treatments included: (a) control; (b) field ultra-fast SO2-generating pad (FUFR) during the 4 h before packaging; (c) dual-release SO2-generating pad (DR) during cold storage; and (d) FUFR pad during the 4 h before packaging in combination with the DR pad during cold storage. The bunches were packaged in 0.5 kg plastic clamshells and placed in carton boxes with a capacity of 10 units each. The treatments were evaluated after 30 and 45 days in cold storage (1 +/- 1 degrees C) by means of the incidence of gray mold, shattered berries, stem browning, bunch mass loss and bleaching. After 45 days, the boxes were removed from cold storage and kept without the pads and liners for 3 days at room temperature (22 +/- 1 degrees C), and the incidence of gray mold, shattered berries and stem browning were assessed. The use of the FUFR pad before packaging and the DR pad during cold storage, combined or not, were efficient at controlling gray mold, keeping the incidence of the disease very low. Both pads were also efficient at preventing the mass loss of grapes, but the percentage of shattered berries was lower when the FUFR pad was used. This allowed grapes to arrive already sanitized to the packing house, and no additional SO2-generating pads were needed, representing savings in economic terms for packaging operations. The stem browning, the chemical properties, and the color attributes of berries were not influenced by any treatment.