Effect of gamma irradiation treatment at phytosanitary dose levels on the quality of 'Lane Late' navel oranges

The objectives of this study were to determine the dose tolerance of 'Lane Late' navel oranges (Citrus sinensis L. Osbeck) to irradiation for phytosanitary purposes, identify the sensory attributes that may be affected by the treatment, and determine which changes, if any, influence consumer liking. 'Lane Late' navel oranges on Carrizo citrange (C. sinensis Poncirus trifoliate) rootstock were irradiated at target dose levels of 200, 400 and 600 Gy (actual absorbed doses were in the range of 100-300, 300-500, and 500-700 Gy, respectively) then stored for 1 d at 5 °C, 3 weeks at 5 °C (to simulate sea shipment to Asia) or 4 weeks (3 weeks at 5 °C and 1 week at 20 °C to simulate distribution to retail following sea shipment). Trained sensory panelists found increased pitting and visual damage in oranges treated at doses of 400 and 600 Gy. Consumer liking scores for appearance were significantly lower for oranges treated at 400 Gy, however, their overall liking scores for those same oranges were not significantly different than control. Color, total phenolic content, vitamin C and ORAC (oxygen radical absorbance capacity) values were not affected by irradiation. Dose effects were seen in terms of visual damage, increased weight loss and increased concentration of certain volatiles and as well as decreased SSC (soluble solids concentration) at doses 400 and 600 Gy. The primary effect of irradiation on fruit quality was external damage and pitting at doses of 400 and 600 Gy. Further research should consider pack configuration and/or combination treatments to possibly mitigate negative irradiation effects on appearance of the fruit.