Meat fraud: Testing to detect species substitution

Acts of fraud relating to meat products are ongoing, and a global issue. A brand’s reputation can be severely compromised should a product be found to be fraudulent.

Consumers rely on the accurate and complete declaration of food constituents to enable them to make product choices that are consistent with their lifestyles.

Testing can be a valuable tool for the routine monitoring of meat authenticity, and should be conducted whenever a case of meat adulteration or contamination is suspected.

What tests are available to investigate meat fraud?

Testing for meat species authenticity is typically performed using either DNA-based methods or protein-based methods.

Proteins consist of unique chains of amino acids that fold into complex 3D structures; and DNA (deoxyribonucleic acid) is made up of unique sequences of nucleotides. The information contained in these chains or sequences serves as a ‘fingerprint’ for the detection of species-specific DNA or protein in food samples.

Which is more suitable: DNA-based testing or protein-based testing?

This depends on the sample type and the testing objective.

DNA-based methods such as PCR are appropriate for raw meat products, while a protein-based detection method such as LC-MS/MS is better suited to processed food products.

FACTS offers a range of species-specific testing options (view our testing catalogue here). It is always best to discuss your testing objectives and fraud concerns with the FACTS team first, to determine which test method is best suited to your needs.

Why are DNA-based methods not always appropriate for processed food products?

Risk of false negative results for processed meat products

Food processing may cause DNA to unwind and fragment into single or short-chain nucleotides. This results in DNA being less readily detected, as the unique information contained in the nucleotide sequence is lost.

Quantification difficulties

Different meat tissue types contain varying amounts of target DNA, and the variability is typically unknown. Different species also have differences in the genomic location and status of target genes, which can influence amplification efficiency and the relative abundance of target genes in a given sample. Furthermore, the composition of meat products (e.g. high fat and water content) can affect DNA recovery efficiency. These factors make quantification by DNA-based methods difficult, and may lead to underestimated results.

Why is proteomics by LC-MS/MS well suited to processed food products?

Proteomics by LC-MS/MS detects peptides – short amino acid chains that result from protein digestion and hydrolysis. Peptides are generally stable in food samples and are unlikely to be modified by food processing, which ensures that they will be detected by the method. This results in a low risk of false negative results, even for heavily processed samples.

Proteins are also abundant in all meat tissue types, and across samples of different species.

Targeted vs non-targeted proteomic methods

Proteins can be analysed using targeted or non-targeted LC-MS/MS methods.

Non-targeted methods collect data without prior knowledge about which peptides will be detected. The detected peptides are identified using a search engine database. Although non-targeted methods can provide a global overview of the proteins present in a sample, these methods generally have lower sensitivity and are less reliable for quantification.

Targeted methods collect data on predetermined peptides that have been carefully selected to ensure good specificity and sensitivity for a particular protein. Specificity can also be controlled by selecting specific and non-specific targets for different food types, eliminating the potential for false positive results.

Qualitative vs. quantitative test methods

Qualitative tests will confirm the absence or presence of certain species from a sample.

Quantitative tests will confirm the levels of a species in a sample. These results may be useful in determining whether a detected species is present due to contamination or adulteration.

Screens vs single-species test methods

A sample can be tested for a single species or for multiple species by a screening test. Screens are generally qualitative, providing an overview of the presence or absence of a range of species in a sample.

FACTS currently offers various screens. View our testing catalogue here, or contact us for more information.

Interpreting test results: when is a product considered contaminated or fraudulent?

South Africa does not currently have any legal threshold levels set for undeclared species in meat products. It is up to manufacturers to follow good manufacturing practices, and to consider the Consumer Protection Act and the ethical and religious impact of contaminated or fraudulent products on certain consumer groups when interpreting results.

In reaction to the 2013 ‘horsegate’ scandal, the UK Food Standards Authority (FSA) set threshold levels for undeclared meat species in comminuted (processed) meat products: 0.1% as an action threshold, where an investigation into the cause of the undeclared species in the product is required; and 1% as a reporting threshold, where findings must be reported to the FSA.

These threshold levels can be used as examples for interpreting results.

For assistance with result interpretation, please contact us. 

Testing for other types of meat fraud

Meat fraud is not only about species substitution; there are multiple ways the authenticity of meat and related products can be compromised. The addition of undeclared compounds such as bulking agents, additives, antibiotics and growth hormones is also an issue, as well as claims relating to origin, breed and production method (organic, grass-fed claims, free range), and frozen and thawed meat sold as fresh. There is no single test that can detect all types of fraud and adulterants. Therefore, additional tests are available and should be applied to detect and investigate some of these types of meat fraud.

Testing for adulterants that pose food safety risks to consumers should always be a priority; for example, testing for the common allergens such as gluten and soy which may be present in meat bulking agents and fillers.

Keep an eye on our website for new content discussing what is feasible for detecting other types of meat fraud. Contact our team of food fraud experts for more information or view our testing catalogue.

Other articles and resources you may be interested in:
Meat fraud: Overview of vulnerabilities
Targeted proteomics: a go-to-method
Gelatine and collagen: authenticity concerns
Comparing test methods: PCR, ELISA & Targeted Proteomics by LC-MS/MS
FACTS Testing Catalogue