Response of different maturity stages of sapota (Manilkara achras Mill.) cv. Kallipatti to in-package ethylene absorbent
Sapota fruits are highly perishable due to their climacteric nature. The rapid softening of fruits is primarily due to high activity of many oxidative enzymes and liberation of ethylene. Harvest maturity plays a crucial role in deciding the marketability of climacteric fruits in general. Attempt has been made to evaluate the response of ethylene absorbent on variable maturity groups of harvested Sapota cv. Kallipatti with the objective to delay the ripening during transit and extend its marketability during storage at ambient condition (27–32 °C & 65–75% R.H.). Harvested fruits having three different degree of ripeness (as maturity indices viz. mature, half-ripe and ripe) were packed with or without ethylene absorbent sachets (Bioconservación, France) in 10 kg CFB boxes and transported from Dahnu to Delhi covering a distant of approximately 2500 KM by truck on road along with conventional packaging as control. The fruits were evaluated immediately on arrival at Delhi and subsequently during storage for various physical, physiological, biochemical and decay parameters. Mature fruits with ethylene absorbent exhibited maximum delay in ripening, low ethylene liberation, weight loss and high fruit firmness. The response of ethylene absorbent to extend the marketability of ripe fruit was not significant.
Response of climacteric-type guava (Psidium guajava L.) to postharvest treatment with 1-MCP
Abstract Guava ( Psidium guajava L. cv. ‘Allahabad Safeda’) fruit harvested at the mature light-green stage were exposed to 300 and 600 nL L −1 1-methylcyclopropene (1-MCP) for 6, 12 and 24 h at 20 ± 1 °C, and held in either cold storage (10 °C) for 25 days or ambient conditions (25–29 °C) for 9 days. Most of the physiological and biochemical changes during storage and ripening were affected by 1-MCP in a dose dependent manner. Ethylene production and respiratory rates were significantly suppressed during storage as well as ripening under both the storage conditions depending upon 1-MCP concentration and exposure duration. 1-MCP treatment had a pronounced effect on fruit firmness changes during storage under both the conditions. The reduced changes in the soluble solids contents (SSC), titratable acidity (TA) and vitamin C content showed the effectiveness of 1-MCP in retarding fruit ripening. Vitamin C content in 1-MCP-treated fruit was significantly higher than in non-treated fruit, and those treated with 300 nL L −1 1-MCP for 6 h. The development of chilling injury symptoms was ameliorated to a greater extent in 1-MCP-treated fruit during cold storage and ripening. A significant reduction in the decay incidence of 1-MCP-treated fruit was observed under both the storage conditions. 1-MCP at 600 nL L −1 for 12 h, in combination with cold storage (10 °C) seems a promising way to extend the storage life of guava cv. ‘Allahabad Safeda’ while 1-MCP at 300 nL L −1 for 12 and 24 h or 600 nL L −1 for 6 h, may be used to provide 4–5 days extended marketability of fruit under ambient conditions.
ATP-dependent S-(2,4-dinitrophenyl)glutathione transport in canalicular plasma membrane vesicles from rat liver.
Uptake of the thioether S-(2,4-dinitrophenyl)glutathione (DNPSG) in canalicular plasma membrane vesicles from rat liver is enhanced in the presence of ATP and exhibits an overshoot with a transient 5.5-fold accumulation of DNPSG. Stimulation by ATP is not caused by the generation of a membrane potential, based on responses of the indicator dye oxonol V. ATP-dependent uptake has an apparent Km of 71 microM for DNPSG and a Vmax of 0.34 nmol.min-1.mg of vesicle protein-1. Protein thiol groups are essential for transport activity as indicated by the sensitivity of DNPSG transport to sulfhydryl reagents. There is competitive inhibition with other thioethers, S-hexylglutathione (Ki = 66 microM), the photoaffinity label S-(4-azidophenacyl)glutathione (Ki = 56 microM), as well as with glutathione disulfide (Ki = 0.44 mM) and with the bile acid taurocholate (Ki = 0.61 mM). GSH (2 mM) or cholate (0.4 mM) does not inhibit. Both glutathione disulfide and taurocholate show ATP-dependent transport in the canalicular membrane vesicles which is inhibited by DNPSG. No ATP-dependent transport is found for GSH. Transport of DNPSG is also inhibited competitively by alpha-naphthyl-beta-D-glucuronide (Ki = 0.42 mM) but not by alpha-naphthylsulfate (2 mM), and there is substantial inhibition with the glucuronides from ebselen and p-nitrophenol. The results indicate that the canalicular transport system for DNPSG is directly driven by ATP and that the biliary transport of other classes of compounds may also proceed via this system.