Postharvest application of sulphur dioxide fumigation to improve quality and storage ability of "red globe" grape cultivar during long cold storage

Abstract

Table grape cv 'Red Globe' is produced in Sicily and in other areas of Southern Italy. This produce is very appreciated by consumers, having the best rankings in the world market for exports and quality. Nevertheless, despite it is a non-climacteric fruit, table grape is very perishable, both after harvest, and during postharvest handling and cold storage. In fact, also at low temperatures, table grape is very sensitive to fungal infection (Botrytis cinerea) and other diseases, like gray mold, which is very aggressive. For this reason, a standard practice is to fumigate table grape with sulphur dioxide (SO2), after storage in chambers. The growing market request of table grape cv. 'Red Globe' enhanced postharvest research on better techniques aimed to maintain the grapes for longer periods, in order to satisfy the demand. Therefore, the object of this study is to assess the effect of cold storage, at 1±0.5 °C and 93±2% relative humidity (RH), of table grape cv 'Red Globe', for 4 months, with low concentrations of SO2 (0.20%), with the aim to extend their post-harvest shelf life. Two samples of Red Globe table grape were stored at 1±0.5°C, the first for control without SO2, and the other treated with low concentration of SO2. Both samples were moved every 15 days, to 20 °C for 3 days, for simulating shelf life and berry decay. Results showed that, 'Red Globe' table grape treated with low concentration of SO2, prolonged its shelf life for three months after harvest. More particularly, firmness, weight loss, total soluble solids content and titratable acidity maintained good values, and rachis and berry decay were inhibited. This technique is a good alternative to the SO2 one or dual release generating pads for maintaining grape quality in extended storage, with lower impacts for the environment and lower costs.