The term mustard oil is used for two different oils that are made from mustard seeds:

• a fatty oil resulting from pressing the seeds,
• an essential oil resulting from grinding the seeds and mixing them with water, and extracting the resulting volatile oil by distillation.

Mustard oil from pressed seeds

This oil has a strong smell, a little like strong cabbage, a hot nutty taste, and is much used for cooking in Bengal and other areas of India and Bangladesh. The oil makes up about 30% of the mustard seeds. It can be produced from black mustard (Brassica negra), brown Indian mustard (Brassica juncea), and white mustard (Brassica hirta).

Mustard oil is composed mostly of the fatty acids oleic acid, linoleic acid and erucic acid, which is considered noxious. At 5%, Mustard seed oil has the lowest saturated fat content of the edible oils.

Due to its high content of erucic acid, mustard oil is not considered suitable for human consumption in the United States, Canada and the European Union, although mustard oil with a low content of erucic acid is available. In India, mustard oil is generally heated until it starts smoking before it is used for cooking. This may be an attempt to attempt to reduce the content of noxious substances.

In Northern India, mustard oil is also used for rub-downs and massages (see ayurveda). In Western countries, the oil is often sold "for external use only" in stores catering to Indians.

Mustard oil from mixing seeds with water

The pungent taste of mustard results when ground mustard seeds are mixed with water, vinegar, or other liquids (or when they are chewed). Under these conditions, a chemical reaction between an enzyme and a glucoside from the seeds of black mustard (Brassica negra) or brown Indian mustard (Brassica juncea) leads to the production of allyl isothiocyanate. This very sharp tasting mustard oil can be extracted by distillation. (The white mustard Brassica hirta does not give allyl isothiocyanate, but a different and milder isothiocyanate).

The essential oil produced in this way, sometimes called volatile oil of mustard, contains more than 92% of allyl isothiocyanate. Allyl isothiocyanate can also be produced synthetically, and is sometimes known as synthetic mustard oil. It serves the plant as a defense against herbivores; since it is harmful to the plant itself, it is stored in the harmless form of a glucoside.

Because of the contained allyl isothiocyanate, this type of mustard oil is toxic and irritates the skin and mucous membranes. In very small amounts, it is often used by the food industry for flavoring. It is also used to repel cats and dogs, and to denature alcohol (make it unfit for human consumption, mainly for tax purposes).

The CAS number of this type of mustard oil is 8007-40-7, and the CAS number of pure allyl isothiocyanate is 57-06-7.

External links

• Canadian Food Inspection Agency
• Isolation of Erucic Acid from Mustard Seed Oil by Candida rugosa lipase