Novel method developed to detect irradiation of cashew nuts and nutmeg
It is based on matrix solid phase dispersion and separation and detection of oxime derivatives of 2-ACBs by high performance–high resolution mass spectrometry (HPLC-HRMS).
The method allowed detection of 2-ACBs in cashew nuts irradiated at 100 Gray and in nutmeg irradiated at 400 Gray.
Irradiation is approved for a variety of foodstuffs and regulated by Directive 1999/2/EC.
However, the only harmonized entry at EU level is for dried aromatic herbs, spices and vegetable seasonings at a maximum overall average absorbed radiation dose of 10 kGy.
Unique indicators of irradiation?
The work was done after Sharma et al found 2-ACBs might not be unique indicators of irradiation, disproving the hypothesis that they are radiolytic degradation products of fat which can serve as sole markers for irradiation treatment of fatty foods.
The authors said a special extraction technique, i.e. supercritical fluid extraction (SFE) using carbon dioxide, with clean-up of the extract using thin-layer chromatography allowed them to identify traces of 2-ACBs in food products.
However, the current research team concluded there is no reason to believe that 2-ACBs are not unique indicators of such treatment.
Researchers looked at the appropriateness of EN 1785:2003 for detection of the radiolysis products of fatty acids in cashew nuts and nutmeg.
They confirmed suitability of the EU standard to detect irradiation of cashew nut samples at average absorbed doses of 1 kGy and above.
The standard has a method for identification of irradiation treatment of food containing fat. It is based on mass spectrometric (MS) detection of radiation-induced 2- ACBs after gas chromatographic (GC) separation.
Samples are irradiated when at least one of the two targeted 2-ACBs is present at a level yielding a signal to noise ratio of at least 3 to 1 (detection limit) using the least sensitive ion, it adds.
“The European Standard EN 1785:2003 allowed the detection of irradiated cashew nut at an irradiation dose of 700 Gy; however, for nutmeg neither 2-DCB nor 2-TCB could be detected at an irradiation dose of 1000 Gy,” said the researchers.
Testing of samples
To investigate irradiation on cashew nut and nutmeg, two samples of each were used.
Each material was subdivided in two for four subsamples of cashew nut or nutmeg. They were irradiated with gamma radiation at an average absorbed dose of 100, 400, 700, and 1000 Gy.
A cashew nut and a nutmeg sample were irradiated at a very high dose between 8.6 and 10.9 kGy to verify that EN 1785:2003 and the developed alternative methods were able to detect the 2-ACBs.
Cashew nut and nutmeg samples purchased in different EU Member States were also assessed to verify that 2-ACBs do not occur in non-irradiated foods.
A total of 26 cashew nut and 14 nutmeg samples were processed with matrix solid phase dispersion (MSPD), derivatised, and measured with HPLC–HRMS. 2-decyl, 2-dodecyl, 2-tetradecenyl or 2-tetradecylcyclobutanone could not be detected in any of them.
Source: Food Chemistry, Volume 201, 15 June 2016, Pages 52–58
“Comparative evaluation of methods for the detection of 2-alkylcyclobutanones as indicators for irradiation treatment of cashew nuts and nutmeg”
Authors: Andreas Breidbach and Franz Ulberth
