Spanish researchers detail a technology that is able to distinguish between 100% raw beef and beef meat samples spiked with only 0.5% (w/w) horsemeat – the level required by European legislation.
The biosensor is able to recognise horse mitochondrial DNA fragment that is absent from other mammals.
"Thus, it is possible to identify selectively and without false positives any type of horse meat, regardless of race," said Dr F. Javier Gallego, researcher of the department of Genetics of the Complutense University of Madrid (UCM).
Current techniques, which are based on immunological, spectroscopic or molecular biology "are often not sufficiently selective to differentiate close animal species”, according to Susana Campuzano, a researcher at UCM and study co-author.
“This is due to the possibility of cross-reactions, or sufficiently reliable in processed products due to the denaturation and degradation of the biomolecules (proteins and nuclear DNA) that are produced by these thermal treatments.”
The study selected mitochondrial DNA fragments instead of nuclear DNA as the former is considered better able to resist possible heat treatments.
Horsemeat scandal
News of this work is made all the more urgent in light of recent cases that highlight the adulteration of foods that depend on a certain purity to achieve a desired taste or nutritional profile.
Incidences of contaminated honey, olive oil and milk pale in comparison to the relatively recent horsemeat scandal that saw the meat enter the food chain and end up in products sold in UK supermarkets.
This event also focused the attention of governments, industry, researchers, and regulatory bodies across the world and involved the large-scale replacement of processed beef products with horsemeat and other undeclared meat products, such as pork, sometimes up to levels of 100% substitution.
Two separate teams from UCM began by first isolating the specific fragment to be detected, designing the appropriate probe for it and preparing the mitochondrial lysates,
The other team then designed an electrochemical biosensor that met the requirements of sensitivity and selectivity demanded by current legislation for the detection of this type of adulteration.
The success of the methodology is made even more so by its ease in adapting to the identification of other meat adulterations by simply selecting the appropriate fragments of the mitochondrial DNA region and capture probes.
Vulnerability of food supply networks
"In addition to moving to the identification of other mammalian DNAs, this methodology could be applied for both the detection of adulterations involving other animal meats and for screening purposes to identify all animal species present in a meat," said fellow study author Dr José Pingarrón.
The study goes on to discuss the biosensing platform’s great portability and versatility that could prove a very promising tool, located at points of vulnerability along food supply networks.
“Moreover, the biosensor offers a very attractive on site alternative to PCR-based methodologies for detecting shorter size DNA sequences in degraded samples to address a range of biological problems such as food analysis, biodiagnostics, environmental monitoring, and genetic screening,” the study concluded.
Source: Analytical Chemistry
Published online ahead of print: DOI: 10.1021/acs.analchem.7b02412
“Disposable Amperometric Polymerase Chain Reaction-Free Biosensor for Direct Detection of Adulteration with Horsemeat in Raw Lysates Targeting Mitochondrial DNA.”
Authors: José Pingarrón et al