Thermoluminescence Detection of Irradiated Fruits and Vegetables: International Interlaboratory Trial

An international interlaboratory trial was conducted to validate thermoluminescence methods for detecting irradiated fruits and vegetables. Five products were used in this study. This paper presents the results from prestudy material, homogeneity testing, details of sample preparation, and participants' results. Prestudy results provided a basis for cross comparison of instruments in different laboratories. A wide range of sensitivities, reproducibilities, and signal-to-background ratios were observed. Homogeneity testing showed that the method can distinguish between nonirradiated and irradiated products, including those bleached with 100 J/cm2 artificial daylight, provided that sensitivity rejection criteria are rigorously applied. Blind results were returned by 9 participants in the form of first and second glow integrals and glow ratios for all samples and a qualitative classification for each product. Of the 387 results reported, 327 valid results were obtained from participants. Where valid data were obtained, correct qualitative identifications were made by participants in all cases. Participants' results and homogeneity testing both confirm the validity of the thermoluminescence method for detecting irradiated fruits and vegetables.

Thermoluminescence Detection of Irradiated Shellfish: International Interlaboratory Trial

An international interlaboratory trial was conducted using thermoluminescence for the detection of irradiated shellfish, aimed at validating the method for routine use. Nephrops norvegicus, mussels, brown shrimps, black tiger prawns, and king scallops were presented as nonirradiated and irradiated to 0.5 and 2.5 kGy. The protocol called for the use of 3 preparation methods: extraction of silicates from whole shellfish by acid hydrolysis and physical separation, and of carbonates from powdered shells. Homogeneity was tested on each product and each treatment. Results verified that all methods were able to distinguish between nonirradiated and irradiated samples regardless of dose. Silicate methods produced better discrimination than powdered shell, and acid hydrolysis showed some evidence of better separation between the 2 doses than the physical method. Participants received each product in each treatment category for blind analysis. Six participants returned results for acid hydrolysis, 7 for physical separation, and 5 for the powdered shell method. Their results confirmed the homogeneity testing. Qualitative results gave 100% correct classification for both silicate methods and 85.3% for powdered shell. Silicate methods are therefore preferable unless only shell is available. Overall, the results confirmed the case for validation.

[Bakery goods from irradiated and unirradiated eggs--detection of irradiation in a processed food]

The detection of radiation-specific degradation products in fat has become an established method which has successfully been applied to egg products. This study is making evident the detectability of irradiated eggs as an ingredient of specified processed foods. Tart layers were produced from both irradiated and non-irradiated liquid whole egg. When the fat components were isolated from the tart layers and investigated by GC/MS, the presence of irradiated eggs could clearly be shown. While the radiation-induced hydrocarbons and 2-alkylcyclobutanones could not be found in unirradiated samples, tart layers from irradiated eggs contained these substances. Especially for the hydrocarbons a satisfying correlation between radiation dose and concentration could be observed. The concentrations of radiation-induced compounds were generally lower in the tart layers than in the liquid egg samples they had been produced from.

[Identification of irradiated pasteurized egg products: a combined method for use in routine control]

Pasteurized egg products (whole egg, egg yolk and egg white) were tested for irradiation treatment in the German food control laboratories in Oldenburg/Niedersachsen and Kassel/Hessen as well as in the food irradiation laboratory of the German federal health office. Gas chromatographic/mass spectrometric measurements on the fat components of egg-products showed clearly whether the product had been irradiated or not. While in unirradiated samples no traces of special hydrocarbons (according to the fatty acid composition of egg) and no traces of the irradiation-specific compound 2-Dodecyl-cyclobutanone were found, irradiated control samples as well as products of two Belgian suppliers contained these substances. Additionally, regarding the rather high time consumption of gas chromatography, electron spin resonance (ESR)-measurements were carried out on the packaging material of egg products. Irradiated packaging material (cellulose) could be easily detected by the appearance of a signal pair in the ESR spectrum (cellulose radical). ESR measurements are very fast and easy to perform so that this method can be used for screening. Microbiological investigations showed remarkably reduced total numbers of microorganisms for some irradiated samples, but the microbiological status is influenced by other factors like storage-time and -temperature, so that microbiological tests can not be used successfully for screening on irradiation treatment.

[Fatal poisonings with propoxur]

The insecticide propoxur (2-isopropoxyphenyl-N-methylcarbamate) acts by blocking cholinesterase. This inhibition is fast and, unlike that brought about by organophosphorus compounds, reversible. The toxicity of propoxur to man is stated to be low compared with that of parathion. Only a small number of fatal intoxications have been published; at the Würzburg University Institute of Legal Medicine eight cases have been observed since 1978. In seven cases death occurred after deliberate oral ingestion of solutions of propoxur with suicidal intent, while in the other, intoxication was accidental, following inhalation of an aerosol containing propoxur. Organs and body fluids were investigated toxicologically and histologically. The results are presented and discussed. Special attention is paid to the combination of propoxur and alcohol.