Temperature Conditioning and Surface Treatments of Grapefruit Affect Expression of Chilling Injury and Gas Diffusion

Abstract

`Marsh' Grapefruit (Citrus paradisi Macf.) were temperature conditioned (7 days at 15C), wiped with hexane, treated with squalene, squalane, or safflower oil (all 10% in hexane), or waxed with a commercial fruit wax (Flavorseal) to determine their effects on weight loss, chilling injury (Cl) symptoms on the peel, and gas exchange. Following 3 weeks of storage at SC, wiping fruit with hexane resulted in a significant decrease in weight loss, but not CI. Temperature conditioning and Flavorseal independently inhibited weight loss and Cl development. Squalene inhibited CI development, but not weight loss. Chilling injury on fruit treated with squalene or Flavorseal was similar in appearance, but significantly less common than that on nontreated fruit. Grapefruit peel accounted for 92% of the gas diffusion of fruit, and resistance coefficients for peel and whole fruit were similar. Less ethane diffused into fruit that were: temperature-conditioned compared with nonconditioned, hexane wiped compared with nonhexane-wiped, and squalene-treated compared with nonsqualene treated fruit. Ethane influx was significantly restricted into squalane- and squalane-treated fruit compared with Flavorseal- or safflower oil-treated fruit. Oxygen and CO2 influx was significantly reduced by Flavorseal, safflower oil, squalene, and squalane. Squalane was the most restrictive of ethylene efflux followed by safflower oil, squalene, and Flavorseal. All of these surface treatments are known to reduce CI on grapefruit. These data indicate that water loss is less important to the development of Cl than has been previously 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 Cl.