12S rRNA mitochondrial gene as marker to trace Sicilian mono-species dairy products

Animal Species Authentication in Dairy Products

Milk is one of the most important nutritious foods, widely consumed worldwide, either in its natural form or via dairy products. Currently, several economic, health and ethical issues emphasize the need for a more frequent and rigorous quality control of dairy products and the importance of detecting adulterations in these products. For this reason, several conventional and advanced techniques have been proposed, aiming at detecting and quantifying eventual adulterations, preferentially in a rapid, cost-effective, easy to implement, sensitive and specific way. They have relied mostly on electrophoretic, chromatographic and immunoenzymatic techniques. More recently, mass spectrometry, spectroscopic methods (near infrared (NIR), mid infrared (MIR), nuclear magnetic resonance (NMR) and front face fluorescence coupled to chemometrics), DNA analysis (real-time PCR, high-resolution melting analysis, next generation sequencing and droplet digital PCR) and biosensors have been advanced as innovative tools for dairy product authentication. Milk substitution from high-valued species with lower-cost bovine milk is one of the most frequent adulteration practices. Therefore, this review intends to describe the most relevant developments regarding the current and advanced analytical methodologies applied to species authentication of milk and dairy products.

Phylogenetic differentiation between Awassi and Hamdani sheep using the mitochondrial 12S rRNA

This study was conducted to assess the role of the mitochondrial 12S rRNA variations in the phylogenetic discrimination between two Iraqi breeds of sheep that differ in geographical distribution. A total of 122 animals (68 Awassi and 54 Hamdani) were included in the study. Direct sequencing of amplicons followed by the construction of a median-joining network and several trees were performed to identify the possible phylogenetic differences between both involved breeds. Genetic diversity, relative frequencies, and analysis of molecular variance (AMOVA) were performed to assess the genetic correlation between both populations. The median-joining network and minimized tree values showed that all observed haplotypes were separated into two groups according to their breed. Comprehensive phylogenetic data revealed only one Asian ancestor for all observed haplotypes. As indicated by AMOVA, the observed diversity was mostly due to between-population variation (1.24836%), while within-population variation (0.91221%) accounted for much less. The currently investigated rRNA amplicons exhibited different mitochondrial manifestations between Awassi and Hamdani breeds. Due to the ability of these 12S rRNA amplicons to mimic the geographical diversity for the currently investigated breeds, it is highly recommended to be used as potent mitochondrial genetic markers among broader ovine sequences.

Caprine and ovine Greek dairy products: The official German method generates false-positive results due to κ-casein gene polymorphism

Caseins are widely used for species identification of dairy products. Isoelectric focusing (IEF) of para-κ-casein peptide is used as the official German method for the differentiation between caprine (isoform A) and ovine (isoform B) dairy products, based on their different isoelectric points. The discrimination between Greek goat and ewe dairy products using IEF has, however, been shown to be problematic because of the existence of the ewe isoform in milk from Greek indigenous dairy goats. This could be due to nucleotide polymorphisms within the goat κ-casein gene of Greek indigenous breeds, which alter the isoelectric point of the para-κ-casein peptide and lead to false positive results. Previous DNA analysis of the goat κ-casein gene has shown high levels of polymorphism; however, no such information is available for Greek indigenous dairy goats. Therefore, 87 indigenous dairy goats were sequenced at exon IV of κ-casein gene. In total, 9 polymorphic sites were detected. Three nonsynonymous point mutations were identified, which change the isoelectric point of the goat para-κ-casein peptide so that it appears identical to that of the ewe peptide. Ten composite genotypes were reconstructed and 6 of them included the problematic point mutations. For the verification of genetic results, IEF was carried out. Both goat and ewe patterns appeared in the problematic genotypes. The frequency of these genotypes could be characterized as moderate (0.23) to high (0.60) within Greek indigenous breeds. However, this is not an issue restricted to Greece, as such genotypes have been detected in various non-Greek goat breeds. In conclusion, IEF based on the official German method is certainly inappropriate for ovine and caprine discrimination concerning Greek dairy goat products, and consequently a new method should be established.