Tracking adulteration of nectar honey varieties using a high-resolution melting qPCR technique validated with melissopalinology

Honey is a highly-valued food product, appreciated due to its organoleptic and health-promoting properties; which both depend on its botanical provenance. In this study, a collection of nectar honey varieties (acacia, buckwheat, linden, rape, and heather) was subjected to extensive physicochemical, melissopalynological, and molecular analyses, to verify if the latter (qPCR-HRM) can be used as a rapid method for determination of the product's authenticity. To this end, the DNA extracted from the honey pollen grains was subjected to a carefully pre-optimized qPCR-HRM analysis. The effectiveness of extracting DNA templates relied on various factors but a significant role played honey pollination degree. The plastidial rbcL barcode was found to be a better option for the taxonomic differentiation with qPCR-HRM when compared to the nuclear targets. The results showed that qPCR-HRM correctly clustered honey samples of the same botanical origin determined by melissopalynology. The qPCR-HRM clustering results were additionally verified by rbcL region sequencing. The most consistent data were obtained for heather honey with over-represented pollen, which results from the generally observed low availability of plastidial DNA in the total DNA extracts. The qPCR-HRM revealed a biological divergence within the honey samples marketed as acacia, as confirmed by melissopalynology.

Automated summary

In this study, various analysis methods were applied to different varieties of nectar honey to verify the feasibility of using qPCR-HRM as a rapid method for determining the authenticity of honey. The study found that the plastidial rbcL barcode was a better option for taxonomic differentiation using qPCR-HRM. The clustering results of heather honey were the most consistent.