Cornmint

Cornmint (Mentha arvensis) is a rather fragile herb with leafy stems up to 60 cm high, lance shaped leaves and lilac-coloured flowers borne in clustered whorls in the axillas of the upper leaves.

It is cultivated in China, Japan, Taiwan, Brazil, Argentina, India and South Africa.

Cornmint oil is produced by steam distillation of the flowering herb. The crude oil contains 60-80% (-)-menthol, 10-20% (-)-menthone, pinene, (-)-menthyl acetate, isomenthone, thujone, phellandrene, piperitone and menthofuran, among others. Constituents vary according to the source.

(-)-Menthol can be isolated by crystallization at low temperature.

The residual dementholized oil is a colourless to yellow liquid with a characteristic minty odour. It still contains ca. 50% (-)-menthol; (-)-menthone and (-)-menthil acetate are other major components.

Dementholized cornmint oil tastes more bitter and stringent than peppermint oil. Thus, the former is used as a cheaper substitute for the latter and for the production of (-)-menthol.