TEMPERATURE CONDITIONING AND SURFACE TREATMENTS OF GRAPEFRUIT AFFECT EXPRESSION OF CHILLING INJURY AND GAS-DIFFUSION

'Marsh' Grapefruit (Citrus paradisi Macf.) were temperature conditione d (7 days at 15C), wiped with hexane, treated with squalene, squalane, or safflower oil (all 10% in hexane), or waxed with a commercial frui t wax (Flavorseal) to determine their effects on weight loss, chilling injury (CI) symptoms on the peel, and gas exchange. Following 3 weeks of storage at 5C, wiping fruit with hexane resulted in a significant decrease in weight loss, but not CI. Temperature conditioning and Flav orseal independently inhibited weight loss and CI development. Squalen e inhibited CI development, but not weight loss. Chilling injury on fr uit treated with squalene or Flavorseal was similar in appearance, but significantly less common than that on nontreated fruit. Grapefruit p eel accounted for 92% of the gas diffusion of fruit, and resistance co efficients for peel and whole fruit were similar. Less ethane diffused into fruit that were: temperature-conditioned compared with noncondit ioned, hexane wiped compared with nonhexane-wiped, and squalene-treate d compared with nonsqualene treated fruit. Ethane influx was significa ntly restricted into squalane- and squalane-treated fruit compared wit h Flavorseal- or safflower oil-treated fruit. Oxygen and CO2 influx wa s significantly reduced by Flavorseal, safflower oil, squalene, and sq ualane. Squalane was the most restrictive of ethylene efflux followed by safflower oil, squalene, and Flavorseal. All of these surface treat ments are known to reduce CI on grapefruit. These data indicate that w ater loss is less important to the development of CI than has been pre viously suggested, and that the beneficial effects of squalene are not the result of an inhibition of water loss. Permeability of grapefruit peel to gases other than H2O vapor may also influence the expression of CI.