How DNA analysis can reveal what’s in your meat

Typical DNA sample, looking like a drop of clear liquid, in a tiny vial

Typical DNA sample, looking like a drop of clear liquid, in a tiny vial.

Identifying the species contained in a piece of droëwors or burger patty is not as simple as pulling it apart and examining it under a microscope. Stellenbosch University used established DNA sequencing technologies as one of the methods to unravel the extent of mislabelling in the South African meat market.

DNA sequencing is the process of determining the precise order of nucleotides within a DNA molecule. Termed the ‘blueprint of life’, these molecules determine who and what you are. Or rather in this case, what you are eating.

While the main study was done by Dr Donna-Maree Cawthorn and Prof Louw Hoffman of the Department of Animal Sciences, they relied on the DNA Sequencing Unit at Stellenbosch University’s Central Analytical Facilities to peek into the smallest part of a sausage’s DNA.

According to DNA analyst, Miss René Veikondis, they allow the researchers to visualise the piece of DNA in which they are interested: “They bring a DNA sample in a miniscule plastic vial, and we hand them back the DNA sequence in a readable text file.”

But first the researchers had to do quite a bit of work to identify the region in the genome that could be used to pinpoint the species contained in the meat products. “In other words, there is a specific section of the DNA where the combination of the nucleotides will indicate whether this is a donkey or a water buffalo or a kangaroo,” she explains.

These sections are then cleaned up in the lab and prepared for analysis. This means that the different species could be identified by looking at less than 1 000 of the billions of building blocks in the DNA cocktail provided. The technology used is similar to those used in paternity tests and forensic analysis in crime investigations.

While DNA sequencing hails from processes developed back in the 1970s, the researchers showed that DNA-based methods can be powerful and highly-applicable tools to monitor the meat industry and support law enforcement.

Did you know?

The combined length of all the DNA molecules in a single human cell can measure up to a few meters if stretched out in a single long thread and consist of over one billion building blocks called nucleotides. The nucleotides are organised into minute structures called chromosomes and these range between 200 nanometres to 20 micrometres in length – in other words a millionth to a thousandth of a millimetre.  According to some calculations the combined length of DNA in all cells in a single human body roughly equates to 70 trips to the sun and back to earth.