Characterisation of Kastamonu honeys by palynological and physicochemical methods

Abstract

Thirty-three honey samples were collected between 2017 and 2018 in Kastamonu Province, in order to characterise the palynological and physico-chemical properties of the honey produced in the western Black Sea region of Türkiye. Melissopalynological characteristics of the honey samples were determined based on the total pollen number in 10 g (TPN-10 g) along with the pollen taxa diversity. The physicochemical properties of the samples including humidity ratio, volatile organic compounds, total phenolic content, fructose/glucose ratio and hydroxymethylfurfural (HMF) content were determined using a refractometer, gas chromatography coupled with mass spectrometry (GC–MS), ultraviolet-visible spectrometry and high-performance liquid chromatography, respectively. Melissopalynological analysis revealed that the honey samples contain 49 taxa, of which 18 were determined at family level and 31 were determined at genus level. The most common taxon was Castanea sativa while the other important taxa were Apiaceae, Asteraceae, Amaranthaceae, Boraginaceae, Brassicaceae, Fabaceae and Lamiaceae. Eleven out of 33 honey samples were monofloral and the remaining 22 samples were multifloral. According to the TPN-10 g results of the honey samples, the total number of pollens in 10 g of Kastamonu honey was between 1051 and 325 108 pollen grains. The moisture ratio was obtained between 11.9 and 18.9% while the fructose + glucose values were between 35.84 and 84.1 g/100 g. HMF content varied between 0.38 and 21.31 ppm while the total phenolic content varied between 39.6 and 138.8 mg GAE/100 g. The GC–MS analysis revealed that the samples contain compounds belonging to the groups of aldehydes, aliphatic acid and its esters, alcohols, hydrocarbons, flavonoids, carboxylic acid and esters, ketones, and sugars.