Triplex real-time PCR assay for the authentication of camel-derived dairy and meat products

Abstract

Authentication of dairy and meat products is important to ensure fair competition, consumer benefit, and food safety. The large difference in price between camel and cow milk may be an incentive to adulterate camel dairy products with cow-derived foodstuffs. However, no studies so far have used triplex real-time PCR with an endogenous control to identify camel and cow origins in dairy and meat products. In this study, we developed a triplex real-time PCR assay based on amplification of mitochondrial 12S ribosomal DNA for the authentication of camel-derived dairy and meat products. This method was applied to identify camel and cow DNA in milk, yogurt, cheese, milk powder, milk beverage, meat products, and mixtures with milk and meat. Concentrations as low as 1 to 5% and 0.1% camel milk and meat, respectively, were detected in the mixtures, and 1 to 5% and 0.1% cow milk and meat, respectively, were identified via this approach. The limits of detection were 0.005 to 0.0025 ng, 0.05 to 0.001 ng, 0.001 to 0.0005 ng, and 0.00025 to 0.0001 ng of DNA in camel milk, camel yogurt, commercial camel milk beverage, and camel meat, and from 0.0025 to 0.001 ng, 0.5 to 0.001 ng, 1 to 0.05 ng, 0.01 ng, 0.001 ng, 0.0005 to 0.00025 ng, 0.0005 to 0.00025 ng, and 0.005 ng of DNA from cow milk, yogurt, cheese, acidic whey, milk powder, beef, beef jerky, and beef sausage, respectively. Different dairy and meat samples of camel and cow origins had a range of authentication limits and limits of detection. The designed triplex real-time PCR assay was shown to be a specific, sensitive, and efficient technique for the identification of camel and cow DNA in foodstuffs.

Animal Species Authentication in Dairy Products

“…Both systems were applied in the estimation of cow's milk of fresh and ripened model cheeses, with the nuclear systems revealing the highest specificity and quantitative performance. Later on, the same group of researchers developed three triplex real-time PCR methods with TaqMan probes targeting the 12S rRNA gene to simultaneously detect an endogenous control sequence and two species, namely cow and mare [132], cow and goat [133], sheep and goat [134] and camel and cow [135]. The approaches were successfully applied to processed dairy products, achieving high sensitivities down to few pictograms of DNA (Table 3).…”

Detecting cow milk in sheep yoghurt by TaqMan real‐time PCR

“…In the study conducted by Hai et al . (2020), camel and cow yoghurts were mixed, and cow yoghurt could be detected at 1% in this mixture. Unlike this study, the presence of cow DNA was investigated by mixing yoghurts made from pure milk instead of making the yoghurt from mixed milk.…”

“…In the study, the detection limit of the PCR method was 0.1 ng DNA, and no species other than the one declared on the label was detected in any dairy product analysed. In the study conducted by Hai et al (2020), camel and cow yoghurts were mixed, and cow yoghurt could be detected at 1% in this mixture. Unlike this study, the presence of cow DNA was investigated by mixing yoghurts made from pure milk instead of making the yoghurt from mixed milk.…”

“…However, the results obtained were parallel to those of our study. In studies that used total genomic DNA, including both nuclear and organelle DNA, to determine the sensitivity of species-specific PCR methods, the detection limit was 0.001-5 ng (Zha et al 2010;Dai et al 2015;Di Domenico et al 2017;Guo et al 2020;Hai et al 2020;Sangthong et al 2021).…”

A systematic review of DNA‐based methods in authentication of game and less common meat species

“…Camel meat is also available in other non-Muslim countries such as Australia and China (Hoffman & Cawthorn, 2014). Because of its limited availability, camel meat is rarely adulterated (Hai et al, 2020). Even Galal-Khallaf et al (2021) did not detect adulteration in their camel samples.…”