Stability of the dithiocarbamate pesticide maneb in tomato homogenates during cold storage and thermal processing

The effect of storage at 5 C and of thermal processing by cooking at 100 C and sterilization at 121 C for 15 min on maneb residues in tomato homogenates leas investigated. Remaining maneb and its toxic metabolite ethylenethiourea (ETU) There measured after each treatment by headspace gas chromatography with flame-photometric detection and by high-performance liquid chromatography with photo-diode array detection, respectively. No significant loss of maneb was observed during cold storage for up to 6 weeks, taking into account analytical variability. Conversely, thermal treatment resulted in substantial degradation of maneb with extensive conversion to ETU. After cooking, only 26 +/- 1% ( +/-SE, n = 8) of initial maneb residues remained in the samples, whilst the conversion to ETU was 28 +/- 1% (mol mol(-1)) (+/-SE, n=4). Sterilization eliminated the residues of the parent compound giving rise to conversion to ETU up to 32 +/- 1% (mol mol(-1)) (+/-SE, n = 4).