Temperature, length of cold storage and maturity influence the ripening rate of ethylene-preconditioned kiwifruit

The effect of temperature, length of cold storage and maturity on the ripening of ethylene-preconditioned (100 mu l l(-1) for 12 or 24 h) kiwifruit was investigated. Low (0 degrees C) temperatures at any point prior to, during or after ethylene preconditioning significantly delayed softening and soluble solids concentration (SSC) accumulation compared to higher temperatures (i.e. 20 degrees C). Freshly-harvested kiwifruit responded to ethylene-preconditioning (100 mu l l(-1) at 0 degrees C for 24 h) by softening faster than control fruit even if harvested 5 weeks after commercial maturity. In contrast, kiwifruit harvested at commercial maturity and stored at 0 degrees C softened faster than the control only if preconditioned with ethylene during the first 2 weeks of storage. Kiwifruit had high respiration rates 1 day after being transferred from 0 to 20 degrees C, but respiration dropped to near base-line levels by day 2. Fruit stored at 0 degrees C always respired faster upon transfer to 20 degrees C than did freshly-harvested fruit and preconditioning with ethylene increased the initial rate of respiration of freshly-harvested fruit but had less of an effect on stored fruit. Ethylene preconditioning did not significantly hasten the climacteric rise in respiration or ethylene production of either freshly-harvested or stored kiwifruit. The climacteric rise of individual kiwifruit began only after fruit softened to less than or equal to 7 N. (C) 1999 Elsevier Science B.V. All rights reserved.