Composition of unique unifloral honeys from the Boreal coniferous forest zone: Fireweed and raspberry honey

Unifloral honeys have been shown to contain variable components which give each honey a special and individual organoleptic nature. The aim of this work was to characterize for the first time the composition and properties of unique and aromatic Finnish unifloral honeys from raspberry (Rubus idaeus) and fireweed (Epilobium angustifolium). Water content, electrical conductivity, pH, diastase and invertase activity, colour, sugar and phenolic content, melissopalynological characteristics and organoleptical properties were analysed. Raspberry and fireweed honey have low electrical conductivity and diastase number and are rich in fructose. Both honeys have six disaccharides, while raspberry honey and fireweed honey have two and three oligosaccharides, respectively. The total number of identified phenolic compounds was twentysix (26), of which twenty-five (25) were found in raspberry honey and twenty-four (24) in fireweed honey. The ratio of phenolic acids to flavonoids was 2.26 in raspberry honey and 0.89 in fireweed honey. In raspberry honey 71% of pollen grains originated from Rubus species and in fireweed honey only about 3% of pollen grains originated from E. angustifolium. Both honeys were light in colour and had weak and pleasant odour and taste, but crystal formation was quick in raspberry honey and slow in fireweed honey. Our results suggest that sensory assessments, sugar content and phenolic acids/flavonoids ratio are the best criteria in distinguishing these two unifloral honeys.