Effect of ozone and sulphur dioxide as postharvest treatment to control Rhizopus rot and quality maintenance of table grape (Vitis vinifera L.)

Abstract

Table grape is one of the most important fruits which is subjected to fungal decay during post-harvest handling, transit and storage. An investigation was made to evaluate ozone (O3) fumigation at the concentration of 7274.4µL L-1, 5455.8µL L-1 and 3637.2µL L-1 and sodium metabisulfite (SMB) as Indian grape guard, African grape guard and SMB powder pouches (0.5g/500g fruit) against Rhizopus rot and their effect on quality of table grapes under ambient storage (33±2°C, RH-37±5%, 12 d). The results revealed, ozone at the concentration of 7274.4µL L-1 and 5455.8µL L-1 O3 recorded significantly least disease severity (0.78; 0.94) and higher retention of berry firmness (82.51; 81.07 N), titratable acidity (0.99; 0.98 %) and least PLW (13.24; 13.58 %), TSS (19.41; 19.57oB) and TSS/Acid Ratio (19.88; 19.88) compared to SMB and inoculated control treatments. In addition, SMB treatments and inoculated control showed high decay by Rhizopus rot on 5th day of storage, therefore they were not evaluated after 5th day till end of storage (12th day). From the above results, we conclude that, ozone is a good alternative to sulfur dioxide treatments in conventional grape production and it could be a suitable technology to use with grapes marketed under ambient chain, where sodium metabisulfite and grape guard release, excess SO2 in ambient condition, moreover it could be also an acceptable technology to use with grapes marketed under “organic” classification, where the use of SO2 is prohibite.