Rhamnus frangula Honey: Screening of Volatile Organic Compounds and Their Composition After Short-Term Heating

Abstract

There is no report on the chemical composition of alder buckthorn (Rhamnus frangula L.) honey and therefore volatile organic compounds (VOCs) were investigated for the first time as well as their composition after short-term heating. The electrical conductivity of the samples was 0.90 - 0.98 mScm-1 (specificity of alder buckthorn honey), and pH values were 4.00 - 4.33. The melissopalynological analysis revealed R. frangula L. as dominant plant species (52-93%) in all samples. Accompanying minor plant species were also determined (Castanea sativa L., Centaurea jacea L., Lotus corniculatus L., Prunus spp., Salix spp., Apiaceae, Asteraceae, Acer spp. and Cornus sanguinea L.). The VOCs from R. frangula L. honey were isolated by headspace solid-phase microextraction (HS-SPME) and ultrasonic solvent extraction (USE) and analysed by GC-FID and GC-MS. To investigate the influence of short-term heating, selected sample was heated 3h at 100 oC with and without H2O addition. The most representative chemical profile of R. frangula L. honey is obtained by HS-SPME containing benzaldehyde, hotrienol and 4-ketoisophorone. USE contributed to the honey characterization, mainly by vomifoliol identification. The majority of compounds found in USE were higher aliphatic alcohols. The influence of short-term heating to R. frangula L. honey is strongly dependent on H2O addition. Namely, more artefacts (furan derivatives, particularly 5-hydroxymethylfurfural) were formed during heating of the honey dissolved in H2O in comparison with direct honey heating.