Essential oil - Seiyu (English spelling) essential oil

Japanese: 精油 - せいゆ(英語表記)essential oil
Essential oil - Seiyu (English spelling) essential oil

Aromatic oils are volatile oils with a unique fragrance obtained from the branches, leaves, roots, bark, trunks, flowers, buds, fruits, etc. of plants. They are generally lighter than water, and are not glycerides like other oils such as rapeseed oil and palm oil. They have different properties, so they are distinguished as essential oils, which means "essence" of the plant. They are the main source of aroma in plants, and have been valued as fragrances in human life since ancient times. The types of plants that produce essential oils (most of which belong to the group called herbs) are relatively limited, and the parent bodies of essential oils that are commercially produced are extremely small compared to the number of plants distributed around the world.

Essential oils are usually complex mixtures of dozens of components, and even if the essential oil is obtained from the same plant, the components and their ratios will vary depending on the part of the plant, place of origin, climate, and handling method.

There are three methods for isolating essential oils from plants: (1) steam distillation, (2) squeezing, and (3) extraction. Refining methods include distillation or decolorization for liquids, and sublimation or recrystallization for solids. Essential oils each have their own unique fragrance, and are relatively unstable, deteriorating easily when exposed to heat or air. They also have strong bactericidal and preservative properties. Chemically, the components of essential oils are broadly divided into oxygen-containing compounds such as alcohols, aldehydes, ketones, acids, and esters, and mono- and sesquiterpene hydrocarbons. It is the former that are related to the fragrance and flavor of essential oils, while the latter are poorly soluble in water and easily degraded by oxidation in the air, so they can be said to be substances that are rather a hindrance to the fragrance and flavor.

[Kikumasa Sato]

[Reference] | Fragrances | Fragrance plants | Herbs

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

植物の枝葉、根茎、木皮、樹幹、花、つぼみ、果実などから得られる特有の芳香をもつ揮発性の油で、芳香油ともいう。一般に水より軽く、菜種油、やし油などの油脂類のようにグリセリドではなく、性質が異なっているので、植物の「精」という意味から精油として区別している。植物のもつ芳香の主体であり、古来人類の生活に香料としての価値を評価されてきた。精油を産する植物(その多くはハーブとよばれるものに属する)の種類は比較的限られており、商業生産される精油の母体は、全世界に分布する植物の数に比べてきわめて少ない。

 精油は通常数十種以上の成分の複雑な混合物であり、同一植物から得た精油でも、その部位、産地、気候、取扱い法が異なれば、精油の成分やその比率も変わってくる。

 植物から分離するには、(1)水蒸気蒸留法、(2)圧搾法、(3)抽出法がある。精製法としては、液体のものは蒸留または脱色、固体のものは昇華または再結晶法がある。精油は、それぞれ特有の香気を有し、熱や空気に接触すると変質しやすく、比較的不安定である。また、強い殺菌力、防腐力を有している。精油の成分は化学的にはアルコール、アルデヒド、ケトン、酸、エステルなどの含酸素化合物と、モノおよびセスキテルペン系炭化水素とに大別される。精油の香気や風味に関係を有するのは前者であり、後者は水に溶けにくく、空気酸化を受けて変質しやすいので、香気や風味に対してはむしろじゃまになる物質といえる。

[佐藤菊正]

[参照項目] | 香料 | 香料植物 | ハーブ

出典 小学館 日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について 情報 | 凡例

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