Evaluation of authenticity and botanic origin of buckwheat honeys on the basis of their physiochemical, phenolic and volatile composition data

Honey is a remarkably complex natural liquid produced by bees from plants nectars, plant secretions and excretions of plant sucking insect. Its composition depend strongly on the plant species, although external factors also play a role, such as seasonal, environmental factors and processing conditions. Honey consists of a supersaturated solution of sugars, of which the main contributors are fructose (38%) and glucose (31%). A wide range of minor constituents is also present in honey, many of which, including phenolic compounds, are known to have antioxidant proprieties. The presence of this substances highlight the role of honey as a nutritional source of natural antioxidants with a wide range of biological effects, such as anti-bacterial, anti-inflammatory, anti-thrombotic, but also anticancer and anticarcinogenic proprieties. Buckwheat honey is a dark honey produced by bees that collect pollen and nectar from the little pink flowers of the buckwheat plant (Fagopyrum esculentum Möench, Polygonaceae), popularly recognized as an excellent honey source and a selective antioxidant and hypolipidaemic nutrient food. In literature have been reported the high antioxidant proprieties of the buckwheat honey, as well as its antibacterial activity. Considering the several health benefits of this honey, the principal aim of this work was the characterization of some buckwheat honeys. Ten buckwheat honey samples, from different collection place, were characterized on the basis of their pollen, physicochemical, phenolic and volatile composition data. Electrical conductivity, optical rotation, pH and sugar composition were the physicochemical parameters with higher discrimination, showing the presence of three blended honeys. Honey volatiles, analysed by solid phase microextraction (SPME) and gas chromatography mass-spectrometry (GC/MS), revealed more than 100 volatile compounds, most of them present in all honey samples even though with quantitative variation. Besides many furfural derivates, 3-methylbutanoc acid was the main volatile compound found in most of the samples. The presence of 2- and 3-methylbutanal, pheynalcetaldehyde, among with 3- methylbutanoic acid confirmed the typical buckwheat aroma of some studied samples and corroborated physiochemical data. HPLC-MS phenolic profile did not show significant differences cross the honeys and p-coumaric and p-hydroxybenzoic acid were found to be the most abundant compounds in all buckwheat honeys. While melissopalynological analysis remains nowadays as the only technique which allows a direct botanical source characterization, physicochemical parameters afford quantitative results, allowing an approximate estimation of the kind of honey and the possible presence of honey blends. Also volatile and phenolic compounds function as important role in honey characterization and improves our knowledge about honey as a source of antioxidants.