EXOGENOUS APPLICATION OF POLYAMINES IMPROVES SHELF LIFE AND FRUIT QUALITY OF MANGO

Abstract

This research aimed to investigate the benefit of postharvest application of polyamines {Spermine (SPM), Spermidine (SPD) and Putrescine (PUT)} on the shelf life and fruit quality of mango (Mangifera indica L. cv Kensington Pride). Polyamine application retarded fruit softness, colour development and reduced physiological weight loss during storage without a significant reduction in ethylene production. Lower concentrations of SPM (0.01 mM), and higher concentrations of SPD (0.5 mM) and PUT (1 mM) were more effective in retarding fruit softening. During fruit ripening, SPM (0.01 mM) exhibited the minimum respiration compared with the control fruit. Analysis of ripe fruit, which were stored for 3 or 4 weeks, showed that polyamine application significantly increased fruit firmness, acidity, ascorbic acid, while reducing the TSS/acid ratio and total carotenoid content compared with the control. The exogenous application of polyamines improved shelf life of mango without having deleterious effect on fruit quality. INTRODUCTION Mango is one of the most popular summer fruit in both domestic and international markets owing to its delicious taste and aroma. However, a short shelf life remains one of the major impediments in the market and to increasing international trade, despite several research efforts in the past to extend its storage life. Mango is a climacteric fruit, often harvested at the mature, hard green preclimacteric stage. The ripening process involves numerous rapid biochemical changes and is triggered by ethylene, whether derived from endogenous or exogenous sources (Wills et al., 1989). Polyamines {Spermine (SPM), Spermidine (SPD) and Putrescine (PUT)} and ethylene production are interrelated, since they share a common precursor (SAM) (Kakkar and Rai, 1993). Therefore, there is a possibility that polyamines may regulate the process of fruit ripening and storage. However, such a relationship between polyamines (PAs) and ethylene has yet to be determined in mangoes. Exogenous application of PAs has reduced fruit softening, and delayed senescence in various fruits (Kramer et al., 1991). The application of SPM (0.3, 3 mM) to papaya as a fruit dip treatment for 30 minutes before ripening at room temperature resulted in delayed softening, lower colour score, but did not retard weight loss. SPM (3 mM) extended the shelf life by up to 2.6 days, while SPD and putrescine at the highest concentrations retarded weight loss, but had no other effects (Purwoko et al., 1998). Mango fruit cv 'Arumanis' were pressure infiltrated (0.72 kg/cm for 3 min) with PUT (1, 3, 10 mM), SPM and SPD (0.3, 1, 3 mM) and then ripened at room temperature (28oC). PAs treatments maintained significantly higher fruit firmness than the controls, and SPM and SPD performed better than PUT (Purwoko et al., 1998). Likewise, the beneficial effects of PAs applications have also been reported during storage of different fruits (Valero et al., 1998, 2002). The effects of postharvest application of PAs on mango fruit during storage, and