Horsemeat adulteration picked up by electrochemical biosensor

Horsemeat masquerading as beef could be a food fraud scandal of the past thanks to the development of a novel biosensor.

A team of researchers from the chemistry and biology departments at the Complutense University of Madrid (UCM), Spain, have found a way to detect horsemeat adulteration in just one hour by developing an electrochemical biosensor based on unique differences in the horse's genome.

The work is published in the journal Analytical Chemistry.

The technology works by recognising a specific horse DNA fragment, absent in other animals but present in the mitochondrial genome of horses. Its sensitivity is such that it can detect adulteration where there is only 0.5 per cent (w/w) of horsemeat in the sample.

"Thus, it is possible to identify selectively and without false positives any type of horsemeat, regardless of race," said Francisco Gallego, researcher in the department of genetics at UCM.

The technology represents a development for the food industry given that traditional detection methods, such as assays, have been based on immunological, spectroscopic or molecular biology techniques, which are not always sufficiently selective and sensitive to differentiate close animal species. This is due to the possibility of cross-reactions, as well as the denaturation and degradation of proteins and DNA during meat processing, said fellow researcher Susana Campuzano, from the analytical chemistry department at UCM.

For this reason, the researchers used mitochondrial DNA (DNA located in a cell's energy-producing structure known as mitochondria) as opposed to DNA located in the cell's nucleus because it is more protected and resistant to processing methods.

Traditional DNA extraction techniques also use the polymerase chain reaction (PCR) to amplify the DNA samples but the Spanish team chose to develop a technique without PCR, saying: "To our knowledge, no PCR-free biosensing strategy has been reported so far for horsemeat adulteration detection."

Instead, the researchers extracted the mitochondrial DNA using a centrifuge and then used magnetic microcarriers with an RNA-probe specific for the DNA to tag the horse fragment and separate it using disposable electrodes. Signal amplification was accomplished using commercial antibody specific RNA/DNA duplexes and a bacterial protein conjugated with a horseradish peroxidase homopolymer.

The researchers said this makes the biosensor an attractive alternative to PCR-based methodologies for detecting shorted DNA sequences in degraded samples.

The "promising tool" can also be easily adapted for the detection of other meat adulterations, the team believes. "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 Jose Pingarron, professor of analytical chemistry at UCM.

The researchers also believe the technology would be suitable for areas more vulnerable to food fraud and adulteration, and where complex laboratory equipment is not available.

The technology comes at a time when there is increased focus on the food supply chain, notably following the 2013 UK horsemeat scandal when horsemeat was found in frozen burgers and ready meals labelled as 100 per cent beef.

Early last month, two UK food executives at the heart of the scam were found guilty and jailed for their role in misleading consumers. Andronicos Sideras (55) – one of the owners of meat producer Dinos & Sons – was jailed for four years and six months for his part on the racket, while Ulrik Nielsen (58), the Danish owner of FlexiFoods, got a three-and-a-half-year sentence. Another man – Alex Ostler-Beech (44), who worked with Nielsen – was sentenced to 18 months, suspended for 12 months.

The plot came to light when delivery orders were mixed up resulting in a surprise spot-check by environmental health officers, who found three horse ID chips in the meat products. Further analysis found that approximately one third of the 12 pallets tested contained "significant amounts" of horsemeat.

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