Putting Claims To The Test Featured

In the wake of scandals undermining product quality and authenticity, what testing methods can be used to assure consumers that products are fit for consumption? By Dr Lauryn Bailey, global marketing manager, Food and Environmental Markets, AB SCIEX

One of the key areas of ethical concern is food product quality control and authenticity and, in particular, the accidental or fraudulent blending of meat from different species. 

This is most problematic for consumers with ethical concerns against consuming pork products, such as Muslim and Judaic communities.  Even the presence of traces of pork in meat-based products and gelling agents in food (ie: in candy, ice cream, and marshmallows) are of high concern to these consumers. 

Another key area which brings about ethical implications are false label claims as seen in the 2013 European meat contamination scandal where traces of horse DNA were identified in beef products sold in several supermarket chains. This also has health implications as some horses are treated with antibiotics that are highly toxic to humans.

 

Detecting Contamination

Meat speciation in the laboratory has traditionally been performed using either polymerase chain reaction (PCR) or enzyme-linked immunosorbent assay (ELISA). PCR utilises an indirect analysis of the meat protein by detecting the remnant DNA rather than the protein directly.  As a result, false negatives could be observed, specifically in overly processed foods, where the DNA may be destroyed during processing.  

Meanwhile, ELISA methodology is based on the interaction of the targeted meat protein with an antibody to that protein. This approach is limited in that each species must be analysed separately and it is highly susceptible to false positive or false negative results, particularly for closely related meat species or if the product has been processed (which could modify or degrade the intact protein).

 

Enhancing Accuracy

Besides PCR and ELISA, a spectrometry-based method has also been developed for detecting pork.

Proteins are extracted from the tissue and digested into peptide fragments; in some samples, SPE is used to remove matrix interferences to enhance results.  By monitoring multiple peptides for each type of meat tissue, the method provides better selectivity to verify the presence of a particular meat tissue within a sample.

Extracts are separated using microflow LC chromatography, which provides excellent separation, peak shape, and sensitivity, enabling labs to achieve limits of detection for some meat species to one percent composition or even less.

MRMs for the peptide markers are detected using QTRAP LC/MS/MS detection for highest specificity for the targeted peptide sequence.  

By identifying the exact peptide sequence, this method enables the distinction between even closely related species—for example, many horse and beef proteins are highly similar and only differ by a few amino acids, so having sequence information is critical to avoid false species assignments.

This LC/MS/MS approach detects those markers to confirm the identity of the peptides and ultimately, the identity of the species in the tissue sample.  

The differences in this method, as compared to existing methods such as PCR and ELISA, lie in the fact that it can detect multiple protein markers of multiple meat samples in a single run with high sensitivity.  

By combining the detection of multiple peptides for each meat species, and the capabilities to get the sequences of those peptides, liquid chromatography and tandem mass spectrometry (LC/MS/MS) is able to overcome many of the limitations of traditional methodologies, particularly the lack of specificity of PCR and ELISA approaches, which can lead to false negative or false positive findings.

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  • Last modified on Tuesday, 03 June 2014 16:11
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