1-METHYLCYCLOPROPENE TREATMENT EFFICACY IN PREVENTING ETHYLENE PERCEPTION AND RIPENING IN INTACT AND FRESH-CUT ‘GALIA’ MELON AND ‘SUNRISE SOLO’ PAPAYA FRUITS

Abstract

The objectives of this study were to determine the physiological responses of intact and fresh-cut melon (Cucumis melo L. var. reticulatus L. Naud. cv. Galia) and papaya (Carica papaya, L. var. Sunrise Solo) fruits in which ethylene perception was blocked through application of 1-methylcyclopropene (1-MCP). The whole fruits were treated with 1-MCP (melon, 1 or 1.5 μL L-1; papaya, 2.5 or 9 μL L-1) for 24 h at 20 ºC and stored at 20 ºC or processed and stored at 5 ºC. Inhibition of ethylene perception via application of 1-MCP delayed the onset of the respiratory and ethylene climacterics and reduced maximum respiration and ethylene production rates of ‘Galia’ fruit ripened at 20 ºC. Softening of intact and fresh-cut ‘Galia’ melon was significantly reduced by 1-MCP, regardless of application time (ripening stage). Yellowing of the fruit surface during ripening was strongly and somewhat irreversibly delayed in 1-MCP-treated ‘Galia’. Papaya fruit (‘Sunrise Solo’) treated with 1-MCP exhibited delayed initiation of the respiratory and ethylene climacterics and suppressed ethylene production during ripening. Softening was significantly delayed in fresh-cut and intact fruit. Papaya treated with 1-MCP retained higher levels of titratable acidity compared with non-1-MCP-treated fruit throughout ripening. The color change of the fruit surface from green to yellow was significantly but temporarily inhibited in 1-MCP-treated fruit. Cell wall modification was studied in intact and fresh-cut ripe papaya fruit stored for 10 days at 5 ºC. Water-soluble polyuronides represented the major pectic fraction followed by the CDTA (1,2 cyclohexylenedinitrilotetraacetic acid)- and Na2CO3-soluble fractions irrespective of 1-MCP. Both hemicellulosic and pectic polysaccharides in intact and fresh-cut fruit showed some changes but this trend was slightly or not affected by 1-MCP. Neutral sugars from pectins and hemicelluloses including galactose, glucose and xylose decreased in both intact and fresh-cut fruit regardless of 1-MCP. Generally, either intact fruit or fresh-cut fruit pre-treated with 1-MCP exhibited little or no significant changes compared with fruit not treated with 1-MCP. The studies presented herein have shown that 1-MCP has potential for extending the useful storage life of intact and fresh-cut melon and papaya fruits by delaying ethylene inducible ripening process