Лимонний мирт

Lemon Myrtle, scientifically known as Backhousia citriodora, is a native Australian plant. It belongs to the family Myrtaceae and is native to the subtropical rainforests of central and south-eastern Queensland, with a natural distribution from Mackay to Brisbane. The species can reach 6 m (20 ft) in height, but is often smaller. The leaves are evergreen, opposite and lanceolate, 5-12 cm long and 1.5-2.5 cm broad, and glossy green. The flowers are creamy-white and are produced in clusters at the ends of the branches from summer through to autumn.

Origin and Production

The harvested leaves are dried for leaf spice, or distilled for the essential oil. The majority of commercial lemon myrtle is grown in Queensland and the north coast of New South Wales, Australia. In plantation cultivation the tree is typically maintained as a shrub by regular harvesting from the top and sides. Mechanical harvesting is used in commercial plantations. Drying lemon myrtle leaves at higher temperatures may improve the citral content of the dried leaves but discolours them more. Myrtle rust, a fungal pathogen, was detected in lemon myrtle plantations in January 2011. It severely damages new growth and threatens lemon myrtle production.

Chemistry

Backhousia citriodora has two essential oil chemotypes. The citral chemotype is more prevalent and is cultivated in Australia for flavouring and essential oil. Citral as an isolate in steam distilled lemon myrtle oil is typically 90-98%. Its oil is the highest-content natural source of citral. The major component of the oil was first thought to be one compound and was named citral because of its lemony aroma and flavor. It is a mixture of the two geometric isomers neral and geranial. Citral is an acyclic monoterpene aldehyde with the formula C₁₀H₁₆O. In a sample of the leaf oil, geranial made up 52.13% and neral 37.65%. Oxygenated monoterpenes, at 91.95%, were the most abundant compound class in that sample. The citronellal chemotype is uncommon and can be used as an insect repellent. Its oil is a source of L-citronellal, whereas many sources contain either the racemic form or the D-isomer.

Culinary Uses

Lemon myrtle is used as flakes in shortbread, as a flavouring in pasta, as whole leaf with baked fish, infused in macadamia or vegetable oils, and made into tea, including tea blends. It is found as a flavor in teas, breads, biscuits, cakes, cheeses, chutneys, jams, pastas and vinegars.

Safety

Because of toxicity investigations on major component citral, topical use at less than 1% in a topical formulation is recommended. The use of essential oils high in citral, such as that of Backhousia citriodora, should be restricted during pregnancy because of a possible teratogenic hazard.