Are your ingredients what you think they are?

‘Super-ingredients’ that come with health and wellbeing claims are often added to ready meals to make them more attractive to consumers. Manufacturers promote the ingredient on their packaging and in their advertising and hope this will be the deal breaker in promoting sales. But, what happens when the super-ingredient isn’t what you thought it was? Can you even tell?

I remember watching a CSI-type TV show where they put the goop from a cadaver’s stomach through a gas chromatograph to see what the victim’s last meal was. The resultant graph had a peak labelled as chicken soup! If only it was this easy.

Last February, following an investigation by the New York Attorney General’s office, four major US dietary supplement retailers were ordered to remove products from sale based on results of DNA barcoding testing. The investigation concluded that a majority of the products tested lacked the target botanical and/or contained unlabelled species.

Was this a fair and reasonable action? As the investigation was based on DNA barcoding tests, the answer is probably no.

Mainstream media presents DNA testing as the acme of reliability to establish authenticity and most of us blindly accept this. After all, DNA testing has provided incontrovertible evidence for forensic investigations, medical diagnostics and paternity testing in humans for more than two decades. But DNA barcoding is not a silver bullet.

DNA barcoding

DNA barcoding was first introduced as a means to identify animal species. The FDA-validated method can be used to distinguish distinct species, such as if the minced meat is beef or pork or whether the fish is barramundi or ling. It was widely used in the ‘horse meat scandal’ that rocked Europe a couple of years ago and works well with fresh or living tissue.

DNA barcoding can be used to identify major plant groups such as grasses and pine trees but falls short when information about specific species is required or when the product has been processed or the DNA has been removed or degraded.

DNA barcoding usually involves:

• sample materials being homogenised;
• extraction of genomic DNA;
• amplification of specific gene regions;
• gene sequencing;
• comparison of result sequence against a known reference material to identify the sample.

Plants are particularly problematic as they are extremely complex and cannot be successfully identified to the species level from just a couple of standard regions, as is possible with animals.

While DNA barcoding using a single gene or standard set of genes may be appropriate for animals, it is not so for plants due to their dramatically different life history characteristics, evolutionary histories and hybridisation.

At one end of the plant spectrum is Ginkgo biloba; these slow-growing trees have no close relatives. This means that their genes are unique and can be easily differentiated from those of other plants. However, dynamic lineages of closely related species, such as Echinacea, are difficult to distinguish genetically due to widespread hybridisation.

The most critical step in using DNA for plant species identification is to locate the genes that contain the appropriate level of variation to allow for differentiation of species. This is not an exercise for the uninitiated and usually requires extensive research into the evolutionary history and biology of the plants being tested. Only after specific genes that distinguish particular species reliably are identified can true identification be achieved.

In fact, the limiting step is not the method underlying DNA barcoding but rather the identification of DNA sequences that can be used to reliably isolate and differentiate between species.

Meanwhile, you are relying on your supplier to deliver what you have ordered and have written onto your packaging. Sadly, it is you, not the supplier, whose reputation will suffer if it is established that what you claim on your packaging isn’t delivered.

Image credit: ©iStockphoto.com/Angelika Schwarz