Reasons some official and, more often, trade laboratory results were overturned included differences in sampling and methods of analysis with some sub-optimal methods used, said the group in its annual report.
“The chemistry or molecular biology of the product or analysis may be overlooked, and stochastic effects can introduce disputes on findings close to legislative limits. Many disputes, however, arise because of lack of awareness of context.
“Contextual oversights we have observed in casework include lack of knowledge of appropriate limits, inappropriate calculation of results, lack of proper application of measurement uncertainty, lack of regard to the population sub-group exposed, over-reliance on instrumental ‘black box’ algorithms, lack of awareness of naturally occurring compounds, poor presentation of results and lack of adequate datasets covering natural variation.”
Example of cases
16 cases were referred to the Government Chemist in its role as referee, all in connection with the Food Safety Act 1990.
The group said the default analytical strategy is multi-replicate analyses on multiple days. Replication with analysis of certified reference materials and of blanks and spiked blanks provide analytical confidence.
It dealt with two cases of animal speciation – one was a Public Analyst’s finding of 46% equine DNA in a sample of Bulgarian pork sausage.
Public Analyst’s results were confirmed and the business put in a guilty plea. This was the first prosecution from the horse meat episode.
The second speciation case involved the identification and labelling of squid.
Retail packs of squid labelled “... frozen New Zealand Squid” and on the back label the ingredients stated “squid” and further information “Produced in New Zealand and packed in the UK from arrow squid caught in the South West Pacific Ocean...”.
The Public Analyst certified DNA extracted from the sample was consistent with that of the Argentine short fin squid but a laboratory acting for the food and business operator reported their portion contained DNA consistent with the label information.
Analysis led Government Chemist to conclude that the sample exhibited a 100% similarity with the Argentine squid and a 99% similarity with the arrow squid.
“In effect they were both correct as far as the information currently known to science is concerned. This emphasises the need for authenticated reference material for cephalopods and more validated sequence information in curated databases,” said the report.
The work is managed and delivered by the Government Chemist team, funded by the National Measurement Office and overseen and advised by the Government Chemist Working Group.
A variety of problems were referred in 2014, additives, animal species identification, food contact materials, GMOs, food labelling, mycotoxins, pesticides and veterinary residues.
The annual report also said published literature suggests genomic DNA may be the preferred target for meat quantitation due to its stable copy number between tissues, whilst mitochondrial DNA could be better for sensitive detection of meat species due to its relative abundance but there is little published evidence.
Experimental data is being produced regarding the application of genomic and mitochondrial assays for the quantitation of meat and offal material.
The biennial Government Chemist conference attracted more than 150 delegates over two-days.
The audience heard from speakers on topics including how isotope ratio measurements can be used to help determine the origin of foods and establish authenticity and the accuracy of labelling.
Dr Derek Craston, government chemist, said as was the case in 2013, authenticity featured heavily in referee analysis and research work and it anticipates it will be a continuing trend.
“Food authenticity has both economic and social impacts; for example, where substitution involves the use of ingredients linked to known allergens,” he said.
“It is reassuring, therefore, that the UK and EU have responded with a number of initiatives including the formation of the UK Food Crime Unit and new allergen labelling laws.
“Fraud takes many forms requiring a range of different detection solutions and molecular biology tools are becoming increasingly important in our armoury for characterising suspect goods.”