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

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

Mustard oil from pressed seeds

This oil has a strong smell, not unlike strong cabbage, a hot nutty taste, and is much used for cooking in Gujarat, Orissa, Bengal, Bihar, Jharkhand, Chhatisgarh, Assam and other areas of India and Bangladesh. In north India, it is mainly used in frying fritters. The oil makes up about 30% of the mustard seeds. It can be produced from black mustard (Brassica nigra), brown Indian mustard (Brassica juncea), and white mustard (Brassica hirta).

Mustard oil has about 60% monounsaturated fatty acids of which 42% erucic acid and 12% oleic acid, it has 21% polyunsaturates of which 6% is the omega-3 alpha-linolenic acid and 15% omega-6 linoleic acid and it has 12% saturated fats (source: USDA food data base item 04583: http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl

Mustard seeds, like all seeds of the (the cabbage-type) Brassica plant family, including canola (rapeseed) and turnip, are uniquely high in omega-3 (6 -11%) and are the most common, cheap and mass produced source of plant-based (thus, vegetarian source) of that uniquely heart healthy omega-3 fatty acid family (see 'Indo-Mediterranean' diet in the links below). Flax (linseed) oil has 55% plant-based omega-3 but is uncommon as a table or cooking oil. Soybean oil has 6% omega-3 but contains over 50% omega-6, the fatty acid that competes with the omega-3 function. Notably, there are no other common sources of plant based omega-3 in Western and Indian diets. Especially when omega-6 intake is kept low, humans can convert the plant omega-3 into one of the fish omega-3's, EPA, in credible amounts, vital for vegetarians.

In India, mustard oil is often heated almost to smoking before it is used for cooking; this may be an attempt to reduce the strong smell and taste. However, high heat can damage the omega-3 in the oil, reducing its unique role in health. Mustard oil was once considered unsuitable for human consumption in the United States, Canada and the European Union due to the high content of erucic acid. This was based on rat studies we now know not to apply to humans. Mustard oil with low erucic acid but good omega-3 content is becoming available. To get around that aversion in Western countries, the oil is often sold "for external use only" in stores catering to Indian immigrants, since in North India, mustard oil is also used for rub-downs and massages (see ayurveda), thought to improve blood circulation, muscular development and skin texture; the oil is also antibacterial.

In India, the attack on mustard oil may be accurately seen as an attempt by large oil, margarine and "vegetable ghee" (almost always a trans-fat) corporations interested in replacing mustard with canola oil, a variety of rapeseed with low erucic acid but good omega-3 content, or simply with other oils such as the zero omega-3 sunflower oil. The East and North Indians have used mustard oil for ages and maintain that it is beneficial to human health; this is now supported by much science, including the Indo-Mediterranean study where mustard seed oil use prevented second heart attacks, see link below. Mustard seed can be cold pressed to extract the oil, conserving the omega-3 content, and it is suitable for short-term moderate frying. The availability to poor populations (and to those with heart disease risk) strongly support its use; it may be THE most heart-healthy product on a food or drug store shelf because of its rare omega-3 content.

Mustard oil from mixing seeds with water

The pungency of the condiment mustard results when ground mustard seeds are mixed with water, vinegar, or other liquid (or even when chewed). Under these conditions, a chemical reaction between the enzyme myrosinase and a glucosinolate known as sinigrin from the seeds of black mustard (Brassica nigra) or brown Indian mustard (Brassica juncea) produces allyl isothiocyanate. By distillation one can produce a very sharp-tasting essential oil, sometimes called volatile oil of mustard, containing more than 92% allyl isothiocyanate. The pungency of allyl isothiocyanate is due to the activation of the TRPA1 ion channel in sensory neurons. White mustard Brassica hirta does not yield allyl isothiocyanate, but a different and milder isothiocyanate.

Allyl isothiocyanate 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 glucosinolate, separate from the myrosinase enzyme. Once the herbivore chews the plant, the noxious allyl isothiocyanate is produced. Allyl isothiocyanate is also responsible for the pungent taste of horseradish and wasabi. It can be produced synthetically, sometimes known as synthetic mustard oil.

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. In northern Italy, for instance, it is used in the fruit condiment called mostarda. It is also used to repel cats and dogs. It will also denature alcohol, making it unfit for human consumption, thus avoiding the taxes collected on alcoholic beverages.

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.

Use of mustard oil in North Indian cultural activities

Mustard oil, though not very popular as a cooking oil in North India, still is intricately embedded in the culture, used in these contexts:

1. It is poured on both sides of threshold when someone important comes home for the first time (e.g. a newly-wedded couple or a son or daughter when returning after a long absence, or succeeding in an exams or election.
2. Used as traditional jaggo pot fuel in Punjabi weddings.
3. Used as part of home-made cosmetics during mayian.
4. Used as fuel for lighting earthen lamps (diyas)on festive occasions like Diwali.

External links

• Canadian Food Inspection Agency
• http://www.ncbi.nlm.nih.gov/pubmed/12433513?dopt=Abstract Effect of an Indo-Mediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean Diet Heart Study): a randomised single-blind trial.
• Isolation of Erucic Acid from Mustard Seed Oil by Candida rugosa lipase
• The Mustard Seed Conspiracy by Vandana Shiva in The Ecologist, July 2001
• Tanuja Rastogi (2004) Diet and risk of ischemic heart disease in India. American Journal of Clinical Nutrition, Vol. 79, No. 4, 582-592, April 2004. Retrieved 2007-01-29
• Alternate oils

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