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Low dose irradiation of fresh iceberg lettuce and fresh spinach is permitted in the U.S. to reduce microorganims; however, there is insufficient data on the effects of low dose irradiation on the plastic packaging for such produce. We investigated the effects of gamma irradiation at 0.5 - 20 kGy on the concentration of four antioxidants: Tris (2,4-di-tert-butylphenyl) phosphite, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(nonylphenyl) phosphite; a slip agent (erucamide); and four antioxidant radiolysis products: Tris (2,4-di-tert-butylphenyl) phosphate, 2,4-di-tert-butylphenol, tris(nonylphenyl) phosphate, and nonylphenol in polyethylene resin. Using accelerated solvent extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS), we found the concentration of antioxidants decreased as the irradiation dose increased. As the irradiation dose increased to 4 kGy, the major products associated with irradiation treatment increased. Erucamide was not significantly affected at doses less than 20 kGy. The results presented in this paper can assist with the safety evaluations of food packaging materials.

Estimating exposure to radiolysis products of polymers is an important part of the regulatory evaluation of packaging materials for use in food irradiation. However, as Koni Grob recently put it, the comprehensive analysis of migrants is a challenge. This paper discusses some of the analytical difficulties and presents results obtained with extracts of irradiated polystyrene and polyamide-6. The results indicate that headspace or thermal desorption techniques may, in some instances, lead to an overestimation of radiolysis product concentrations. It is concluded that validated analytical methods and a better understanding of the underlying radiation chemistry would greatly facilitate the safety assessment of irradiated packaging materials.