Effects of exogenous putrescine on improving shelf life of four plum cultivars

Four plum cultivars ('Golden Japan', 'Black Diamond', 'Black Star' and 'Santa Rosa') were treated with 1 mM putrescine, and then stored at 20 degreesC. Storage duration was different for each cultivar, but the effect of putrescine in terms of increased shelf life, delayed ripening process, and higher quality attributes when compared with controls was significant for all cultivars. In addition, putrescine-treated plums showed delay and/or reduction on ethylene production, the intensity of reduction being dependent on the maximum of ethylene production at the climacteric peak. Also, higher fruit and flesh firmness, lower soluble solids concentration and titratable acidity evolution, reduced weight loss and delayed colour changes were found after putrescine treatment during storage. Moreover, higher putrescine and spermidine levels (free forms) were observed in putrescine-treated plums. The results revealed that plum storability could be extended by putrescine treatment due to its effect on delaying the ripening processes. (C) 2003 Elsevier B.V. All rights reserved.