Decolorization - decolorization

This refers to the process of removing the color from the coloring liquid. The decolorization and refinement of fats and oils is carried out using high-performance adsorbents such as activated clay (natural bleaching clays, such as Fuller's earth and acid clay, whose main component is hydrated aluminum silicate, which are activated by treating them with sulfuric acid, etc.), activated carbon (which is expensive and not used alone), or chemicals with oxidation and reduction properties. However, chemical methods cannot be applied to edible fats and oils, and are generally limited to industrial products. Other methods include heating, light, and liquefied solvent extraction. In petroleum refining, clay is also used as an adsorbent for decolorization. Activated clay is more expensive than natural bleaching clay, and since the waste clay contains oil, there is a large loss of oil. However, activated clay is more effective than natural bleaching clay, and can be used sufficiently for fats and oils that contain a considerable amount of free fatty acids. Activated clay is used at about 120°C, and decolorization is generally carried out under reduced pressure. This is to prevent the fats and oils from being oxidized and deteriorated by oxygen in the air during the decolorization process.

[Kazuo Fukuzumi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

着色液の色を除く処理をいう。油脂の脱色精製は、活性白土（フーラー土、酸性白土のような含水ケイ酸アルミニウムを主成分とする天然漂白土などを硫酸などで処理して活性化したもの）、活性炭（値段が高く単独では使用されない）のような優れた吸着剤、あるいは酸化・還元作用を有する化学薬品により行われる。ただし化学的方法は食用油脂に適用できず、一般に工業用製品に限定される。そのほか加熱、光線、液化溶剤抽出法などがある。石油精製においても、脱色に白土が吸着剤として用いられる。活性白土は天然漂白土よりも値段が高く、また廃白土中に油を含むために油の損失が大である。しかし活性白土は、天然漂白土よりも効力が勝り、かなりの量の遊離脂肪酸を含む油脂にも十分用いうる。活性白土は約120℃で使用され、現在一般に減圧脱色が行われる。これは、脱色操作中に油脂が大気中の酸素により酸化されて変質するのを抑制するためである。

［福住一雄］

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