of figs was inspected at a UK port by Port Health officials. The harvest had been certified compliant by sampling and analysis prior to shipment to the UK. Port Health used an elaborate sampling protocol to reflect the fact that mould contamination tends to be patchy rather than evenly distributed. Three official sub-samples were taken, each divided again into three – one for the public analyst, one for the importer and one held in reserve in case of a dispute. The public analyst found the consignment to be non-compliant – aflatoxin B1 was above safe limits of 2µg/kg – but the importer’s results disagreed. The third, retained portion of each sub-sample was sent to the GCP to resolve the dispute. At GCP, we test every sub-sample
three times, on three separate days, alongside appropriate control materials. Accompanying samples were spiked with known quantities of aflatoxins so that the proportion recovered from analysis could be factored into the final measurement. The analysis involved optimised solvent extraction, immunoaffinity chromatography clean up, liquid chromatography (LC) separation with post column derivatisation and fluorescence detection. The identity of the measured toxins was confirmed by LC-tandem mass spectrometry (LC– MS/MS), the gold standard of molecular identification. In this example, our findings confirmed those of the public analyst, that the consignment was non-compliant.
40+
A haulage company was fined £25,000 plus £4500 costs for importing feed containing banned animal remains
a 95% confidence interval – an interval within which we may reasonably assume the ‘true’ value lies.) Since food law is criminal law, the burden of proof is to the criminal standard of ‘beyond reasonable doubt’. Thus, where the expanded measurement uncertainty as a 95% confidence interval straddles the limit, it does not breach the required forensic standard. This is an important feature of all forensic casework and is becoming common practice in all food safety work. In general, over the past five years GCP has tended to confirm public analyst findings on aflatoxins, reflecting the availability of robust analytical methods, a high level of expertise in the public analyst service and sampling methods that have evolved to deal with ‘hotspot’ inhomogeneity.
Number of disputed incidents of food contaminated with aflatoxins sent to LGC as a referee between 2005 and 2011
Figure 1 on page 27 shows the dataset for aflatoxin B1. Sub-sample A was above the limit which, although B and C were compliant, meant that the consignment was refused entry into the UK. The dataset (Figure 1) illustrates the complex decision-making accompanying modern food safety regulation at the trace level. For sub-sample B, although one of the mean results was above the limit, the expanded measurement uncertainty straddled the limit. (No measurement is truly exact, the expanded measurement uncertainty describes the dispersion of results around the mean or average value and is usually expressed as
Nitrofurans The GCP has also been called in to act as a referee for a number of cases involving nitrofuran veterinary residues, which are carcinogenic. Nitrofuran residues in food – especially shellfish – present a somewhat more challenging test. Before their 1995 ban in food-producing animals in the EU, nitrofuran veterinary antibiotics were widely used. Again there are problems of inhomogeneity in the distribution of these substances in food, and the parent drugs have a very short half-life in animals, so we use metabolite markers for monitoring purposes. The problems are compounded by the fact that one of the marker compounds, semicarbazide (SEM), which is used to signal misuse of the parent drug nitrofurazone, does not solely arise as a metabolite of this drug: positive findings have also been associated with the use of breadcrumbs and other bread products arising from azodicarbonamide, a flour treatment agent that is not permitted in the EU. More intriguingly, SEM may occur naturally in the shell of crustaceans, including crabs, langoustines and shrimps. We have overcome this problem by analysing the inner core of shellfish meat because SEM detected in wild- caught shrimp, and therefore presumably untreated, seems to be surface-associated. In 2011, GCP investigated four
Above: Stained (Alizarin red) bone fragment – note the characteristic red staining, morphology and lacunae (black dots in the stained particle). Magnification ~ 200x
cases of disputed findings of nitrofuran marker residues in imported food and in each case overturned the official control laboratory (OCL) findings. In two of the cases GCP reported a nitrofuran marker metabolite to be present but at a concentration less than the reference limit at which the consignment would be banned from entering the food chain. As a consequence, we published a comprehensive advice note on nitrofuran analysis on our website. This is a ‘one- stop-shop’ outlining the position in European law, an explanation of how the marker metabolite is analysed, a summary of how SEM may be found in sources other than nitrofurazone, and a description of measurement uncertainty. Since then the number of disputes has diminished with only one so far in 2012 in which we upheld the OCL findings.
Food law is criminal law
Animal remains in organic wheat The BSE crisis 30 years ago, with its tragic human consequences, had an enormous impact on food law and the agrifood sector. The epidemic was generally thought to be caused by a rogue prion in processed animal remains fed to cattle, giving rise to an invariably fatal vCJD in humans consuming the infected meat.