Milk Adulteration: Detection of Bovine Milk in Caprine Dairy Products by Real Time PCR

Abstract

Milk adulteration is an international social problem. Consumption of adulterated milk may cause serious health problems and a great concern of the food industry has been raised. In this study, a method based on the polymerase chain reaction (PCR) principle was validated for detecting cow’s milk in goat's dairy products. A total of 40 goat's dairy products commonly consumed in Greece, were tested. Various concentrations, from 0.01 to 90%, of cows’ milk in goats’ milk samples were prepared for DNA extraction and further PCR analysis. Selection of highly polymorphic regions within the cow and goat mitochondrial D-loops, showing low homology between the two species, allowed to choose specific primer pairs for detection of cow and goat DNA. After electrophoresis, cow DNA was characterised by the fragment of the size of 300 bp, goat DNA by the fragment of 444 bp. The detection limit of the PCR method was 0.01% while sensitivity and specificity of the method were both 100%. Goat dairy products samples were tested for the presence of cow DNA. Thirty six out of forty (90%) that were tested, were found to produce cow-specific PCR product in addition to goat PCR product while only two samples gave goat-specific product only. The results are disappointing in terms of the food labelling honesty but on the other hand PCR is again a quickly, easy and reliable method that could be used for extended adulteration screening.

Novel and Sensitive Touchdown Polymerase Chain Reaction Assays for the Detection of Goat and Sheep Milk Adulteration with Cow Milk

“…The double peaks of the above samples demonstrated the amplification of both bovine and goat milk components (Figure 4). Using real-time PCR assays and TaqMan probes, Tsakali et al (2019) previously showed that 90% of commercial goat milk and dairy products in the Greek market were adulterated with cow's milk [7]. These results, combined with the results of our study showing a high proportion of cow's milk adulteration, are disappointing when considering the honesty of food labeling.…”

“…Assessing the authenticity of dairy products is important not only from an economic perspective but also because of consumers' medical requirements (e.g., allergies to certain milk proteins), religious practices, or other personal choices [4]. Another important issue is the protection of the characteristics and reputation of traditional cheeses with Protected Designation of Origin (PDO) and Protected Geographical Indication (PGI), as described in Commission Regulation (EC) 1151/2012, which sets requirements for milk from certain species and/or in certain quantities [5][6][7].…”

Speciation and milk adulteration analysis by rapid ambient liquid MALDI mass spectrometry profiling using machine learning

“…The detection and analysis of adulteration in milk is often undertaken by techniques based on PCR or enzymelinked immunosorbent assay (ELISA) [14][15][16][17] . These techniques can be very fast and sensitive but are dependent on the ligand and substrate interaction.…”

Species identification of ruminant milk by genotyping of the κ-casein gene

“…The procedure of DNA authentication assumes the possibility of detecting partial substitution of the declared type of milk by molecular genetic analysis of unique gene loci (Agrimonti and Marmiroli, 2018;Kalogianni, 2018;Agrimonti et al, 2019). The most common method for species identification in milk and dairy products is PCR followed by electrophoresis and hybridization-fluorescence detection of amplification products (Choopan et al, 2017;Di Domenico et al, 2017;Cosenza et al, 2019;Tsakali et al, 2019;Di Febo et al, 2020;Tsirigoti et al, 2020). Additional authentication approaches based on the length polymorphism of restriction fragments of amplified DNA (PCR-RFLP) have also found their application along with methods of hybridization, sequence, and biosensor analysis of the corresponding nucleotide sequences of mitochondrial and nuclear genes (Abdel-Rahman and Ahmed, 2007;Tillmar et al, 2013;Ripp et al, 2014;Abdelfatah et al, 2015;Beltramo et al, 2017;Kounelli and Kalogianni, Species identification of ruminant milk by genotyping of the κ-casein gene R. R. Vafin, 1 A. G. Galstyan, 2 S. V. Tyulkin, 1 Kh.…”