Impact of estragole and other odorants on the flavour of anise and tarragon

Since estragole has been described as potent carcinogen and did not show any flavour impact on the odour of fennel, the flavour of anise and tarragon was examined by combinations of instrumental and sensory analyses. In anise fruits, trans-anethole, 2-isopropyl-3-methoxypyrazine, and anisaldehyde showed high flavour dilution (FD) factors, followed by those of eugenol, cis-anethole, estragole and linalool. Quantitation of the odorants showing higher FD factors in anise tea, and calculation of odour activity values (OAVs) by dividing the concentrations of the respective compound by its recognition threshold in water revealed the highest OAV for trans-anethole, followed by those of anisaldehyde and estragole. Still, an aroma impact of estragole next to trans-anethole could be neglected, due to former sensory studies of aqueous models of fennel tea. For tarragon, AEDA revealed the highest FD factors for eugenol, 7-methoxycoumarin, β-ionone, 2-isopropyl-3-methoxypyrazine, estragole and linalool. Of these, estragole and 7-methoxycoumarine were most abundant in tarragon leaves, showing contents of 2900 and 220 mg/kg, respectively. To calculate OAVs, the contents of potent odorants were divided by their odour threshold in starch or cellulose, as these were the main constituents of the leaves. In this way, β-ionone and eugenol showed the highest OAVs of 5862 and 2653, repectively, followed by estragole (OAV = 460), cis-1,5-octadiene-3-one (OAV = 140), vanilline (OAV = 139) and 2-isopropyl-3-methoxypyrazine (OAV = 130). Therefore, it was concluded that β-ionone and eugenol made the greatest contribution to the overall flavour of tarragon, whereas estragole and the other odorants were of minor importance.