Comparison of hydrodistillation and ultrasonic solvent extraction for the isolation of volatile compounds from two unifloral honeys of Robinia pseudoacacia L. and Castanea sativa L.

A comparative study of ultrasound-assisted extraction (USE) with the mixture pentane:ether (1:2) and hydrodistillation (HD) with the same trapping mixture is presented for the isolation of volatile compounds from two unifloral honeys of Robinia pseudoacacia L. and Castanea sativa L. All HD isolates contained many thermally derived artefacts (especially phenylacetaldehyde with lower percentages of furfural, cis- and trans-linalool oxides and others). USE method gave the most representative profile of all honey volatiles (without artefacts). In addition, USE enabled extraction of low molecular weight semivolatile markers (especially benzoic, vanillic and phenylacetic acids) that were not extracted by HD. In this regard, low percentage of benzoic acid (0.7-7.4%), vanillic acid (0.0-1.6%) and phenylacetic acid (0.5-4.1%) was determined in Rp USE extracts, while Cs USE extracts contained phenylacetic acid (20.2-23.5%) as the major constituent with low percentage of benzoic acid (2.5-5.5%).