Quis custodiet – a Review of the Resolution of Disputed Chemical Results in the UK Official Feed and Food Control System 2010 – 2011

Michael J. Walkera and Kirstin Grayb

(a) Referee Analyst, Government Chemist Programme in LGC, Teddington, Middlesex, TW11 0LY, UK and to whom all correspondence should be addressed michael.walker@lgcgroup.com

(b) Government Chemist Programme in LGC, Teddington, Middlesex, TW11 0LY, UK,

This paper is based on a presentation made at the 2012 Government Chemist Conference – Safe Authentic Food, Policy & Enforcement Challenges & Opportunities held on 8-9 May 2012 at the Royal Society, London.


EU Regulation 882/2004 harmonises official controls on feed and food and provides for businesses subject to those controls to have an analytical second opinion. UK law predates this safeguard by over 100 years. The regulatory landscape in the UK is a complex one with policy set by central government and enforcement mainly a local government responsibility. Analysis by official food and feed control laboratories “the OCL system” provides the underpinning measurement science. Chemical aspects of food and feed safety, composition and labelling are dealt with by Public Analysts and Agricultural Analysts (generally the same official). Should an analytical dispute arise a retained portion of the control sample may, in statutorily defined circumstances, be submitted as a technical appeal to the Government Chemist for a definitive investigation, the “referee analysis”.

This paper describes Government Chemist referee casework in the calendar years 2010 and 2011 and provides an opportunity to assess the performance of the technical appeal safeguard and the control system in the limited number of complex cases where appeal has been invoked.

The OCL system in the UK faced continuing funding challenges in 2010 and 2011 but in general performed well in areas where capability has been developed such as in aflatoxin analysis where Public Analysts’ and Agricultural Analysts’ findings were confirmed on technical appeal in 5 out of 7 (71.4 %) cases. However much more dispersion is evident in aflatoxin results between laboratories in animal feed samples than in food samples. Since largely the same laboratories are involved it is clear that sampling, and in particular the lack of a requirement for high shear mixing with water to form a slurry prior to splitting the samples into parts, is the main source of the variation. It is recommended that sampling and sample preparation should be harmonised in the feed and food areas.

OCL performance was less good in the more problematic area of drug residue analysis. Of six nitrofuran marker metabolite cases (all on imported crustaceans) only one (17 %) was completely upheld. In 3 cases (50 %) a residue was confirmed present but at a concentration below the limit at which the consignment should be prohibited from entry into the UK. Research published in 2011 demonstrated that the marker for nitrofurazone, semicarbazide SEM, is naturally occurring in crustacean shells and in two cases (33 %) the Government Chemist confirmed SEM not detected in the core flesh of the animals overturning the OCL findings. We published a comprehensive advice note on nitrofuran analysis and since then the number of disputes has diminished with only one in 2012 in which the OCL findings were upheld. It is recommended that proposed better markers for nitrofurazone, such as its cyano derivative, should be further investigated and that the sampling of imported crustaceans should be reviewed to achieve better homogenisation prior to sample subdivision.

The diversity of measurement methods surveyed in the paper is evident and indeed represents only a fraction of the range of techniques OCL’s and the Government Chemist must competently deploy to ensure the system is effective and responsive.

In animal feed analysis issues persist around tolerances, vitamin determinations and interpretation of Regulation (EC) No. 767/2009 and will be the topics of a separate case study paper.

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