Fungal Honeydew Elements as Potential Indicators of the Botanical and Geographical Origin of Honeys

The present study applied indicator value analysis as a novel approach to estimate honey authenticity: microscopic indicators of honey origin were identified based on the distinct fungal content of honeys from different sources. The abundance and the IndVal index of 34 selected fungal spore types were quantified in 82 melissopalynological honey samples originating from various honeydew (Pinus, Abies) or nectar sources using multivariate statistical approaches. A dissimilarity matrix of honey samples was obtained by computing Bray-Curtis coefficients, and the distances were visualized using non-metric multidimensional scaling. K-means clustering was applied to sample coordinates to create a classification based on the frequency of selected fungal taxa. Strikingly, the resulting clusters were on a high level of agreement with the melissopalynological or geographical classification of samples. Various fungal taxa were shown to characterize groups of honey samples with a significant indicator value: floral honeys (Metschnikowia reukaufii), Pinus honeydew honeys (Capnobotrys sp., Antennatula sp.), Abies honeydew honeys from Greece (staurospore and scolecospore types) and honeydew honeys from Italy (Tripospermum spp. and Excipularia fusispora). Having revealed that the mere presence of distinct fungal taxa can indicate differences in the botanical and geographical source of honeys, the present findings encourage the confirmation of honey origin also by recording the occurrence of given honeydew elements during routine melissopalynological analysis.