Фенхель

What it is

Fennel most probably originated from southern Europe and the Mediterranean. Fennel has been used for centuries in the Mediterranean area as an aromatic herb and also in folk medicine. Florence fennel, or finocchio, is a selection with a swollen, bulb-like stem base that is used as a vegetable. In mature fennel about 95% of the oil is located in the fruit.

Sweet and bitter fennel

The major compound of sweet-fennel oil is (E)-anethole, at up to 70-80%, which is responsible for the anise fragrance and sweet taste. The (E)-anethole content of bitter-fennel oil is only half that of sweet fennel, whereas the fenchone content is higher. Fenchone is considered a character-impact constituent of bitter-fennel oil. The oil obtained from sweet fennel possesses a finer odour and flavour than that from bitter fennel. A sweet-fennel oil from Italy contained 87.1% (E)-anethole, 4.7% limonene, 3.5% (Z)-anethole and 2.1% fenchone. A bitter-fennel oil from Italy contained 81.9% (E)-anethole, 10.2% fenchone and 4.9% limonene.

Variation between cultivars

In three Egyptian cultivars, trans-anethole accounted for 61% of the oil of azoricum, 46% of dulce and only 5% of vulgare. Estragole was the major compound in the oil of the vulgare cultivar at 58%, against 12% and 6% in azoricum and dulce. Pinene, limonene and fenchone were found in all three oils. Under four different cultivation conditions, the fruit oil of sweet fennel differed in its constituents, especially trans-anethole, estragole, fenchone, limonene and α-pinene.

Constituents

Fenchone is a monoterpenoid and a ketone, and it is a constituent of the essential oil of fennel. The d-fenchone enantiomer occurs in pure form in wild, bitter and sweet fennel plants and seeds. Anethole is a phenylpropanoid that contributes a large component of the odor and flavor of fennel. Estragole is an isomer of anethole, differing in the location of the double bond, and is also a component of fennel. Other phytochemicals found in fennel fruits include polyphenols, such as rosmarinic acid and luteolin, in minor content.

Production

In 2014, India produced 60% of the world output of fennel, with China and Bulgaria as leading secondary producers. Production data for fennel are combined with similar spices: anise, star anise and coriander. The estimated world production of essential oil from bitter fennel is about 28 t, that of sweet fennel about 255 t.

Regulation and safety

Estragole is suspected to be carcinogenic and genotoxic, as is indicated by a report of the European Union Committee on Herbal Medicinal Products. Under the European Pharmacopoeia (2nd edition), the estragole content must be kept below 10%. The IFRA Standard on estragole sets maximum acceptable concentrations in the finished product for 12 product categories. In Amendment 51 these concentrations range from 0.00021% to 0.11%.

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Related: Allspice · Anethole · Anise · Asafoetida · Baking Spices · Bay Leaf · Biryani · Caraway