Low temperature storage and modified atmosphere packaging of carambola fruit and their effects on ripening related texture changes, wall modification and chilling injury symptoms

Storage of mature green (stage 1) carambola (Averrhoa carambola L. cv. B 10) fruit at 5 degreesC maintained fruit firmness, inhibited the solubilization and depolymerization of chelator-soluble wall polyuronides and significantly reduced the increase in pectinesterase and beta-galactosidase activities. At 10degreesC, the fruit exhibited reduced rates of firmness loss, and associated polyuronide solubilization and depolymerization, as well as the increase in pectinesterase, beta-galactosidase, polygalacturonase and beta-(1,4)-glucanase activities being markedly retarded compared to fruit held at ambient temperature (28degreesC). Storage at both 5 and 10degreesC also retarded colour change and reduced water loss. However, chilling injury (CI), as characterised by skin browning, was induced at these temperatures. The CI symptoms were noticeable in fruit kept for 10 and 20 days at 5 and 10degreesC, respectively. The physiological and biochemical responses of the stage I carambola fruit kept at 10 degreesC for 7, 14 or 21 days prior to ripening at ambient temperature showed that the incidence and severity of CI symptoms increased with time of exposure to low temperature (U). Cl symptoms other than skin browning that were manifested upon returning the cold-stored fruit to ambient temperature were enhanced rate of water loss and colour development, as well as accelerated texture loss, which corresponded with an accelerated increase in cell wall modifying enzyme activities. Modified atmosphere packaging (MAP) in low density polyethylene film of carambolas held at 10 degreesC (LT) markedly retarded the decline in tissue firmness and the development of fruit colour, restricted water loss, and suppressed the incidence of CI. The retardation of fruit softening by MAP and/or LT, which correlates closely with delayed solubilization and depolymerization of the chelator-soluble polyuronides, may partly be attributed to suppression of the increase in activity of the major wall hydrolases. Suppression of the enzyme activities in fruit under MAP also appears to contribute to increased tolerance of the carambolas to CI incidence. (C) 2004 Elsevier B.V. All rights reserved.