Quantitation and Seasonal Variation of Key Odorants in Propolis

Propolis is a fragrant material produced by bees and is commonly used as an ingredient in food, beverage, and consumer goods industries. Application of a comparative aroma extract dilution analysis (cAEDA) to volatiles isolated from propolis over three consecutive years afforded 48 odorants with flavor dilution (FD) factors ≥ 4, including 21 compounds not previously reported in propolis. Despite differences in FD factors of some compounds, the overall temporal variation in the odorants was low. Compounds with FD ≥ 64 were quantitated by stable isotope dilution assays (SIDAs), and odor activity values (OAVs) were calculated. A total of 22 compounds showed OAVs ≥ 1, including ( E)-isoeugenol (clove; OAV 3700), linalool (floral; OAV 380), butanoic acid (sweaty, rancid; OAV 370), and 3-phenylpropanoic acid (floral; OAV 270). An odor reconstitution model prepared from deodorized beeswax and the 22 odorants in their natural concentrations closely matched the olfactory profile of authentic propolis. The results of this study will help to establish a basis for future research on the variability of propolis sourced from different geographical locations, produced by different bee species, and collected from different botanical sources, all of which are largely unknown.