Common aroma-active components of propolis from 23 regions of China.

BACKGROUND The study of propolis odorants by gas chromatography-olfactometry-mass spectrometry has rarely been put into practice until now. This study aimed to investigate the common odorants of 23 samples of Chinese propolis and analyse the relationship between the principal components and the regions where the samples had been obtained. RESULTS By using dynamic headspace sampling, gas chromatography-olfactometry-mass spectrometry and two internal standards, the principal aroma-active components of 23 propolis samples were analysed qualitatively and quantitatively. The common aroma-active components were compared with each other by principal component analysis from concentration, odour activity value (OAV) and sensory evaluation score. The components with high OAVs were acetic acid, 2-phenylethyl acetate, and naphthalene, in decreasing order, which approximated the sensory evaluation scores. On the discrete-point map the first three principal components seemed to be grouped into three patterns, while four samples were outliers. CONCLUSION The concentrations of aroma-active components were closely related to the regions from a discrete-point map by the first three principal components. It was confirmed that components with high concentrations did not always play important roles in odour contribution, for odour level was linked with their threshold. OAVs could reflect the level of odour exactly according to the approximate result from the comparison between OAVs and sensory evaluation scores.