Hans Lenstra has been at the Faculty of Veterinary Medicine, Utrecht University since 1990. His research focuses on investigating the genome, evolution, and genetic diversity of domestic ruminants. After contributing to the identification of species-specific repetitive DNA elements and the development of species-identification tests, he is now enthusiastically engaged in genomic analysis of livestock breeds to create molecular reconstruction of the history of domestication.
Food forgery is an age-old problem that has recently resurfaced with a vengeance (see here). Today, meats are being labeled as coming from animals that we like to eat, but they might be something else entirely. Instead of beef, cheap meat from the noble horse is used; tasteless turkey substitutes for chicken; pork is served to people whose religion forbids them to eat it; even the involuntary consumption dogs, cats and rats has been reported. And it is not just meat: cheap fish is being colored and served as salmon.
Italian mozzarella cheese is labeled ‘di bufala’ (from expensive water buffalo milk) when it has been made using normal milk, and on and on... In most cases, these practices do not harm our health: meat is meat. You may also wonder why horses should be exempt from consumption. However, consumers have the right to choose and to be protected against the fraudulent food. Despite the recent headline-grabbing cases, species substitutions are readily identifiable. In fact, protein-based or immunochemical species identification tests were developed 30-40 years ago and rapid, sensitive and versatile DNA-based assays have been available for 20 years. Several projects for improving species detection and traceability tests have been sponsored by the European Union and hundreds of reports have appeared in the scientific literature. Our research group was one of the first to develop DNA-based identification tests. It proved not too difficult. DNA is abundant in most meat samples, even after curing, boiling, baking or autoclaving. And all of the methods tried, including hybridization to species-specific satellite DNA; restriction-enzyme cleavage of amplified mitochondrial DNA, and quantitative PCR with species-specific primers, have worked as predicted. There are now ready-to-use kits available, based on quantitative real-time Taqman PCR with primers and probes that match the mitochondrial DNA of the species to be detected. This approach can be automated, allowing thousands of samples to be processed at minimal cost. These assays are quantitative, although the species detection is not since the amount of DNA per gram of tissue is highly variable and one species may be detected with a higher sensitivity than another. However, as qualitative tests, they robustly identify species substitutions or admixtures. Other tests, based on multiplex DNA, generate DNA fragments with lengths dependent on the species and can be used to detect several species simultaneously.
So, with sound detection methods available, why are we still being cheated on our meat? The answer is that the tests have never been introduced as part of routine food inspection and are used only on suspect samples. And the reason for this? Funding. Priority is given to food-related problems that more directly threaten our health. The past decade has witnessed a number of scares, including several livestock epidemics, new and dangerous human pathogens, such as Enterotoxigenic E. coli (ETEC) and influenza variants, and forbidden contaminants, such as dioxin and antibiotics. Even the detection of genetically-modified organisms (GMOs) in food production, which in America is no issue at all, has taken priority over species fraud in some European countries. Thus, attention has been distracted from checking species origins of foods. This has opened the door to fraudulent traders, who never hesitate to step in. Authorities should be aware that the safety of food can only be guaranteed if we are sure of the species it comes from. It’s time to marshal modern DNA technology and clamp down on food cheats once and for all.
Newsletters
Receive the latest analytical science news, personalities, education, and career development – weekly to your inbox.
