Šiso

Shiso is native to the mountainous regions of China and India, but is now found worldwide. Its leaves occur in several forms, including red, green, bicolor and ruffled. Shiso is perennial and may be cultivated as an annual in temperate climates. Red shiso, called akajiso, is used to give umeboshi, the pickled plums, their red color. In red perilla, anthocyanins are responsible for the deep red and purple hues of the leaves, while in green perilla they are either absent or present in very low concentrations.

Perillaldehyde is a monoterpenoid with an aldehyde group, found most abundantly in perilla. It is the most characteristic component of the leaf essential oil of Perilla frutescens. In Perilla frutescens, (S)-limonene undergoes two oxidation steps, through perillyl alcohol, to give perillaldehyde. The characteristic aroma-active compounds of perilla leaves include ketones, particularly perilla ketone, egoma ketone and isoegoma ketone. Wild shiso is rich in perilla ketone, a potent lung toxin to some livestock.

Perilla essential oil is a complex mixture of approximately 150 to 200 different compounds. Chemotypes have been described from the main components of the oil, among them perillaketone, perillaldehyde, elsholtziaketone, citral and phenylpropanoids such as myristicin, dillapiole and elemicin. In accessions collected in South Korea, the PA type contained 57.7% limonene and 19.8% perillaldehyde, and the PK type 89.8% perillaketone. Together, the PA type (41.9%) and the PK type (38.8%) made up most of these accessions. The composition of the oil is subject to environmental factors, including humidity, soil conditions, temperature, seasonal variations and harvest timing.

Shiso is extensively used in Japanese cuisine, where red, green and bicolor varieties are used for different purposes. The biggest producer of shiso for the food market in Japan is Aichi Prefecture, with 3,852 tons, or 37.0% of national production (2008 data). Within Aichi, the city of Toyohashi produces the most shiso in Japan.

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