Effect of pre-harvest calcium chloride and ethanol spray on quality of 'El-Bayadi' table grapes during storage

Abstract

Grapes (Vitis vinifera L.) are highly perishable due to postharvest fungal decay and softening. The effects of pre-harvest calcium chloride (CC) (at 1 or 2 %) and ethanol (at 10 or 20 %) spray at 30 and 7 days before harvest on quality of 'El-Bayadi' table grapes during cold storage at 0 °C ± 1 plus 1 day of shelf life at 20 °C were evaluated. Pre-harvest spray of CC and ethanol at both low and high concentrations significantly decreased berry decay percentage during storage compared to control. The combination between CC and ethanol also decreased decay compared to control but was less effective than each one alone. In this respect, there were no significant differences between low and high concentration of CC and ethanol. In all treatments, decay was recorded after 30 days of storage and significantly increased to reach 26.3 % after 50 days. CC spray alone, at both concentrations, increased weight loss percentage compared to control and most other treatments. However ethanol spray especially at 20 % decreased weight loss compared to other treatments except for 10 % ethanol spray. The combination between CC and ethanol, however, increased weight loss compared to control except for, 1 % CC plus 20 % ethanol and 2 % CC plus 10 % ethanol. Weight loss percentage increased during storage to reach 2.30 % after 50 days of storage. However, the overall quality characteristics of berries as firmness, TSS, acidity, TSS/acid ratio, pH, vitamin C, total phenols and soluble tannins were not negatively affected by both CC and ethanol spray treatments. Also, both CC and ethanol spray caused neither foliar damage on the vines nor significant changes in berry quality. It is concluded that pre-harvest spray of 1 % CC or 20 % ethanol could be suggested as practical alternatives to synthetic fungicides and SO2 to decrease postharvest decay and improve quality of 'El-Bayadi' table grapes.