Detection of 2,4,6-trichloroanisole in microorganism-free irradiated raisins by solid-phase microextraction and GC-MS

The occurrence of 2,4,6-trichloroanisole (TCA) in nonprocessed dry-on-the-vine (DOV) and Thompson seedless irradiated raisins extracted by solvent-free solid-phase microextraction (SPME) was confirmed using gas chromatography/mass spectrometry. The 42 kGy (kilo Gray) dose irradiated DOV and Thompson seedless raisins incubated in five growth media were shown to be free of microorganisms. The quantity of TCA in the irradiated raisins was 0.39±0.05 ng/kg compared with 0.56±0.17 ng/kg in nonirradiated samples. The observation supports the view that raisins biosynthesize a minute but detectable quantity of TCA. The SPME fiber (divinylbenzene/carboxen/polydimethylsiloxane) method was simpler and quicker than the Likens-Nickerson extraction method for TCA determination. The biochemical mechanism of TCA production in raisin grape is unknown, but information in the biochemical literature of abundant phenolic substrates in grape berry, the presence of methyltransferases in Vitis tissues and of a chlorinating system provides a plausible basis for further investigation of the process.