Detection of Species Substitution in the Meat Value Chain by High-Resolution Melting Analysis of Mitochondrial PCR Products.

Substituting high commercial-value meats with similar cheaper or undesirable species is a common form of food fraud that raises ethical, religious, and dietary concerns. Measures to monitor meat substitution are being put in place in many developed countries. However, information about similar efforts in sub-Saharan Africa is sparse. We used PCR coupled with high-resolution melting (PCR-HRM) analysis targeting three mitochondrial genes-cytochrome oxidase 1 (CO1), cytochrome b (cyt b), and 16S rRNA-to detect species substitution in meat sold to consumers in Nairobi, Kenya. Out of 107 meat samples representing seven livestock animals, 11 (10.3%) had been substituted, with the highest rate being observed in samples sold as goat. Our results indicate that PCR-HRM analysis is a cost- and time-effective technique that can be employed to detect species substitution. The combined use of the three mitochondrial markers produced PCR-HRM profiles that successfully allowed for the consistent distinction of species in the analysis of raw, cooked, dried, and rotten meat samples, as well as of meat admixtures. We propose that this approach has broad applications in the protection of consumers against food fraud in the meat industry in low- and middle-income countries such as Kenya, as well as in developed countries.

Antimicrobial activity of essential oils of Ocimum gratissimum L. From different populations of Kenya.

Hydro-distilled volatile oils from the leaves of Ocimum gratissimum L. (Lamiaceae) of 13 populations of different silvicultural zones were evaluated for antimicrobial activity against gram positive (Staphylococcus aereus, Bacillus spp.) and gram negative (Escherichia coli, Pseudomonas aeruginosa, Samonella typhi, Klebisiella pneumoniae, Proteus mirabilis) bacteria and a pathogenic fungus, Candida albicans. All the essential oils are active to the tested microbiles with different strength. The highest antimicrobial activity against gram positive bacteria (Staphylococcus aureus) and gram negative bacteria (Pseudomonas aeruginosae and Proteus mirabilis) was observed from the eastern Kenya (Meru) oil. Meru oil was the best and its effectiveness was consistent on nearly all the microbes tested. The oil from the plant growing in the coastal region of Kenya (Mombasa) showed the best effect only on gram negative bacteria (Escherichia coli and Proteus mirabilis). Both oils (Meru and Mombasa) were dominated by monoterpenes accounting for 92.48% and 81.37% respectively. The monoterpene fraction was characterized by a high percentage of eugenol (68.8%) for Meru oil and 74.10% for Mombasa oil. The other major monoterpene was methyl eugenol (13.21%). Camphor (0.95%) was observed only in the Meru oil. (Cis)-Ocimene, (trans)-ocimene and beta-pinene were present in both Meru and Mombasa oils. The sesquiterpenes present in fairly good amounts in both oils were germacrene D and (trans)-caryophyllene. The minor sesquiterpenes were alpha-farnesene (0.85%) and beta-bisabolene (0.74%) which were present in the Meru oil only.