Referee analysis of suspected irradiated food

The Government Chemist has been required by statute to act in cases of dispute between traders and UK regulators for over 130 years. Recently, the Laboratory of the Government Chemist (LGC) received its first case of two food samples, chilli powder, that were alleged to have been irradiated, contrary to European Law, (“the referee samples”). The confirmatory method of detection requires the use of irradiation facilities, which LGC does not possess, so it was necessary, for the first time in the history of the Government Chemist function, to sub-contract the work. This paper describes the manner in which the work was organised to ensure that the evidence was provided by expert laboratories in such a way that it was fit for use in court. In particular, aspects of quality assurance essential to the detection of irradiation in blends are described. Analysis was carried out using two standard techniques; photostimulated luminescence and thermoluminescence in each of two laboratories. Both reported the referee samples as positive and correctly identified irradiation in blends of irradiated and non-irradiated chilli powder, at concentrations as low as 1% irradiated material. A second case, consisting of a sample of Guarana powder, was submitted shortly after the first and was treated in a similar manner. On the basis of the result reported by the Government Chemist, the owner of this sample accepted a formal caution from the food authority and paid the prosecution costs.