Dr Ali Raza Awan and Lala Rukh
The availability of pure food is one of the fundamental rights of the consumer. Food adulteration has threatened not only the third world countries like Pakistan where economy is already on its last legs but developed countries are also faced with it. A common man uses different kinds of food in a day but is unaware of the true ingredients even whether that food particle is halal or haram. Moreover this problem directly hits the general health of the public. So food adulterators are playing havoc with the lives of the common people.
The fish industry is also the victim of this fraudulent business. Among various meat products the most substituted and mislabeled one is fish meat in comparison with chicken mutton or beef, because of its greater number of species and difficulty in identification. Only an expert can recognize the exact species of fish. In fish market every salesman is supposed to sell Rahu (Labeo rohita) as it is the most popular amongst general public. People shop various other species like Grass carp, Silver carp, Mori, Thela and Gulfam under the same label that is Rahu. It is because the general public is unaware of the identification of fish species. It is a technical task and cannot be performed without the assistance of an expert.
DNA Barcoding is a modern technique to identify the organisms to species level. This methodology is based on the scanning of a particular region of the mitochondrial DNA. The name DNA Barcoding figuratively refers to the way an infrared scanner univocally identifies a product by using the black stripes of the Universal Product Code (UPC). The genes of mitochondria especially Cytochrome c oxidase 1 (CO1) and Cytochrome b (cyt b) are considered standard for species delimitation and identification.
The whole procedure is very easy and time saving requiring minimal human resource.
Mitochondrial DNA is extracted from the given sample. The mt DNA is present in high copy number in cell and that is why can be extracted in a high yield. Moreover its traces are present even in processed and cooked samples too. This is the reason that this technique is helpful in tracing the processed and cooked food samples, Specific primers for amplification of mt gene/s are designed using different softwares. They attach to their target genes of the template DNA due to their complimentarity at particular temperature and help amplifying them through the polymerase Chain Reaction (PCR). PCR amplification is confirmed by Agarose Gel Electrophoresis and the amplified products are visualized as a single compact fluorescent band of expected size under UV light. The PCR products are sequenced in both directions using dideoxy chain termination direct Sanger Sequencing Method to reveal genetic variations in amplified fragments. The sequencing data is analyzed using different softwares, easily available online. It is an easy and fast implemented method for the identification of unknown, ambiguous and mislabeled fish meat.
