Characterization of the key aroma compounds in rape honey by means of the molecular sensory science concept

By application of aroma extract dilution analysis (AEDA) on the volatile fraction isolated by solvent extraction and solvent-assisted flavor evaporation (SAFE) from unifloral rape honey harvested in July 2009, 28 odor-active areas could be detected within a flavor dilution factor (FD) range of 4-2048. The highest FD factors were found for (E)-β-damascenone (cooked apple-like), phenylacetic acid (honey-like), 4-methoxybenzaldehyde (aniseed-like), 3-phenylpropanoic acid (flowery, waxy), and 2-methoxy-4-vinylphenol (clove-like). Twenty-three odorants were then quantitated by application of stable isotope dilution assays, and their odor activity values (OAV, ratio of concentration to odor threshold) were calculated on the basis of newly determined odor thresholds in an aqueous fructose-glucose solution. The highest OAVs were calculated for (E)-β-damascenone, 3-phenylpropanoic acid, phenylacetic acid, dimethyl trisulfide, and phenylacetaldehyde. Quantitative measurements on a rape honey produced in 2011 confirmed the results. A model mixture containing the 12 odorants showing an OAV ≥ 1 at the same concentrations as they occurred in the rape honey was able to mimick the aroma impression of the original honey. The characterization of the key odorants in rape flowers from the same field suggested 3-phenylpropanoic acid, phenylacetic acid, and three further odorants to be transferred via the bees into the honey.