If you want to know about real potential dangers that can arise from food products, allergens are front and center. With the obligation to label allergens, producers and retailers are also responsible for ensuring that even the unintentional presence of allergens is either ruled out or labelled appropriately.
Using DNA testing, the GBA Group also offers the analysis of genetically modified organisms (GMOs) as well as the determination of animal species. The latter is becoming increasingly important because of authenticity checks and in order to uncover food fraud.
What is GMO?
In contrast to traditional cultivation, the GMO process involves direct intervention in the genotype of a living organism. GMO typically entails the insertion of blueprints (genes) from unrelated organisms. These lend the newly constructed organism completely new characteristics, which could not have been achieved through classic crossbreeding or cultivation.
The following example perfectly illustrates the enormous potency of genetic engineering: Roundup Ready™ soy (MON 04032-6) is a soybean into which a glyphosate-resistant gene has been introduced. Glyphosate is the active agent in Roundup, a common weed killer that is lethal to almost all plants. Roundup Ready™ soy, however, can survive contact with the herbicide. This means that entire fields of Roundup Ready soy can be sprayed with herbicide, killing all other plants in the designated area. The benefit of planting Roundup Ready™ soy is only realized if the fields in use are to be treated extensively with glyphosate.
Today, agriculture plays host to numerous genetic engineering applications, with vastly different aims. Whatever one thinks about the topic, the fact remains that consumers have a right to choose between GMO products and so-called “GM-free” products. If GMO or ingredients based on GMO components are used in foodstuffs, this must be stated on the packaging.
How can GMO be identified in foodstuffs?
The simplest, safest and most cost-efficient way to identify different nucleic acid sequences – including those, which have been genetically modified – is real time PCR. It is an extremely sensitive process, hence tiny quantities of the target organism can be identified. Furthermore, this simple (qualitative) test can provide a rough estimate of the concentration of the target organism in the sample. If a more exact reading is required, a quantitative test can be performed to establish the ratio of the target gene to a specific reference. Real time PCR is the chosen method if specific organisms are to be identified in a given sample. It is equally well suited to testing animal species used in sausage, the carryover of numerous allergenic ingredients in allergen-free products or the presence of viruses in foodstuffs.
Real time PCR can identify the smallest traces of modified DNA sequences in foodstuffs, with different approaches depending on the question formulated.
Screening methods entail checking samples for DNA sequences, which are commonly used in GMO. Thanks to a sophisticated selection of various screening elements, a single sample can be tested for a wide variety of GMOs. If one or several screening elements can be identified, it can thus be established that the sample contains one or more GMO elements – but it is not yet certain which or how much GMO is contained.
Genetically engineered modification of an organism and the resultant clone are described as an “event”. On a simplified level (and hence not entirely accurately), one could consider an event to be equivalent to a type. Event-specific identification seeks to determine specific GMOs. This is crucial, as there as numerous GMOs which are NOT admissible in foodstuffs.
Event-specific identification is generally used as a quantitative measure.
If GMO has been identified in a sample, it is important to determine how much GMO there is in relation to the individual ingredient (e.g.: 5% GM soy in relation to the soy proportion of the sample). Real time PCR makes it possible to assign a reliable value to the quantitative proportion of GMO identified.
A variety of methods can be deployed to identify allergens in foodstuffs.
Allergen identification using real time PCR:
Allergens are indentified indirectly by establishing the DNA of the allergenic target organism. For example, if a sample indicates the presence of celery DNA, then it is reasonable to expect the sample to contain the allergenic substances pertaining to celery. DNA itself is not allergenic.
This method is advantageous in many cases, as numerous allergenic plants contain various allergenic substances which change during production and are therefore no longer identifiable. DNA is extremely stable and can undergo many processes unaltered.
Allergen identification using ELISA
ELISA is a highly specific assay based on antibody reactions. The ELISA method tests a sample for specific allergenic proteins. As a quantitative method, it is ideally suited to ascertaining the gluten content of gluten-free products, for example. This is significant, as there are clearly delineated guidelines regarding gluten, which is not the case for other allergens.
ELISA is superior to PCR in terms of testing for “hen’s egg protein” as albumen contains very little DNA in relation to egg proteins. The ELISA test is considerably more reliable than PCR in this case.
The high specificity of real time PCR can also be applied to identifying different animal species in samples. For instance, the faintest traces of pork can be detected in sausage products – a test which is routinely carried out for HALAL certification of foodstuffs.
Quantitative identification of animal species
Quantitative identification of animal species in foodstuffs is possible in principle, but highly prone to error. In unknown samples, the results are estimates at best, either in terms of ingredients or carryovers. This is relevant, for example, when testing to see if cow’s milk has been added to buffalo mozzarella or to determine whether a sample of minced beef contains traces of pork or indeed is a mix of pork and beef.
With some evidence, it is necessary to understand exactly how the method in question functions in order to evaluate the results: for example, wild boar can be distinguished from some breeds of domestic pig using real time PCR. In isolated cases, the findings can be misleading and therefore an unexpected result should be taken as an indication to check more thoroughly rather than immediately accepted as proof.
We offer the available evidence in spite of this reservation, as in many cases it can provide reliable information to help identify a product. In GBA‘s molecular biology laboratory, samples are examined by experts who themselves have participated in the development and validation of evidence.
Identification of animal or plant species and fungi using sequence analysis
(e.g., true dry rot, fish species, crustaceans ...)
The identity of an unknown sample can be determined using DNA sequence analysis. To this end, small particles of highly variable DNA are reproduced through PCR and their base sequence determined. The species from which the DNA originates can be identified through the sequence. This universal method can, in principle, be applied to all species.
The evaluation of sequence data requires expert biological knowledge. It is imperative to scrutinize the results exactly as there is potential for error at various points. Qualified biologists at the GBA laboratory study every sequence to ascertain its quality and assess the plausibility of all sequence data before releasing the results of identification tests.