Effect of Salicylic Acid and SO2 Generator Pad on Storage Life and Phenolic Contents of Grape (Vitis vinifera L. 'Bidaneh Sefid' and 'Bidaneh Ghermez')

Postharvest life of table grapes is usually shortened by berry softening, berry drop, stem browning and its desiccation and also fungal decay. In the present study, the effects of salicylic acid (SA) and an SO2 generator pad on grape postharvest storage life and its phenolic composition were studied. Harvested clusters of 'Thompson Seedless' ('Bidaneh Sefid') and 'Bidaneh Ghermez' were treated by salicylic acid (SA) at four concentrations, 0, 1, 2 and 4 mmol/L and stored at 0 degrees C up to two months with or without SO2 generator pad. SA treatment significantly increased both cultivars' storage life. SA at all three concentrations effectively reduced water loss and fungal decay and increased berry firmness. Furthermore, SA at 2 mmol/L significantly reduced rachis browning rate. In contrast, 4 mmol/L SA slightly showed higher rachis browning than 1 or 2 mmol/L. The SO2 generator pad reduced fungal decay and rachis browning more effectively than the control. In both SA and SO2 generator pad treatments total soluble solids, titratable acidity and pH of berries were not different from the control. However, results showed that SA treatment followed by the SO2 generator pad treatment significantly enhanced both cultivars' storage life and their overall quality. In addition, total phenolic contents were increased by SA treatment during storage. The highest contents were obtained in 4 mmol/l. However, the SO2 generator pad had no effect on total phenols. The concentrations of quercetin and catechin were higher in SA treated berries. These results demonstrate that SA treatment and the SO2 generator pad together have better potential for increasing table grapes' storage life and quality.