Sesame oil

Composition

Sesame oil is composed of the following fatty acids: linoleic acid (41% of total), oleic acid (39%), palmitic acid (8%), stearic acid (5%) and others in small amounts.

History

Historically, sesame was cultivated more than 5000 years ago as a drought-tolerant crop and was able to grow where other crops failed. Sesame seeds were one of the first crops processed for oil as well as one of the earliest condiments. Sesame was cultivated during the Indus valley civilization and was the main oil crop. It was probably exported to Mesopotamia around 2500 BC.

Sesame oil is thought to have originated in the Indus Valley of North India, but spread from there throughout Asia.

Manufacturing process

Sesame seeds are protected by a capsule which only bursts when the seeds are completely ripe. This is called dehiscence. The dehiscence time tends to vary, so farmers cut plants by hand and place them together in an upright position to continue ripening until all the capsules have opened. The discovery of an indehiscent mutant (analogous to nonshattering domestic grains) by Langham in 1943 began the work towards development of a high-yielding, dehiscence-resistant variety. Although researchers have made significant progress in sesame breeding, harvest losses due to dehiscence continue to limit domestic US production.

Sesame seeds are primarily produced in developing countries, a factor that has played a role in limiting the creation of large-scale, fully automated oil extraction and processing techniques. Sesame oil can be extracted by a number of methods, depending on the materials and equipment available.

In developing countries, sesame oil is often extracted with less-expensive and manually intensive techniques such as hot water flotation, bridge presses, ram presses, the ghani process, or by using a small-scale expeller. In developed countries sesame oil is often extracted using an expeller press, larger-scale oil extraction machines, or by pressing followed by chemical solvent extraction.

Sesame oil can also be extracted under low-temperature conditions using an expeller press in a process called cold pressing. This extraction method is popular among raw food adherents because it avoids exposing the oil to chemical solvents or high temperatures during extraction.

While some manufacturers will further refine sesame oil through solvent extraction, neutralization and bleaching in order to improve its cosmetic aspects, sesame oil derived from quality seeds already possesses a pleasant taste and does not require further purification before it can be consumed. Many consumers prefer unrefined sesame oil due to their belief that the refining process removes important nutrients. Flavour, which was traditionally an important attribute was best in oils produced from mild crushing.

Sesame oil is one of the more stable natural oils, but can still benefit from refrigeration and limited exposure to light and high temperatures during extraction, processing and storage in order to minimize nutrient loss through oxidation and rancidity. Storage in amber-colored bottles can help to minimize light exposure.

Sesame oil is a polyunsaturated (PUFA) semi-drying oil. Commercial sesame oil varies in colour from light to deep reddish yellow depending on the colour of the seed processed and the method of milling. Provided the oil is milled from well-cleaned seed, it can be refined and bleached easily to yield a light-coloured limpid oil. Sesame oil is rich in oleic and linoleic acids, which together account for 85% of the total fatty acids. Sesame oil has a relatively high percentage of unsaponifiable matter (1.5-2.3%) in India and in some other European countries. It is obligatory to add sesame oil (5-10%) to margarine and generally to hydrogenated vegetable fats which are commonly used as adulterants for butter or ghee.

Sesame seed market

The market for sesame oil is mainly located in Asia and the Middle East where the use of domestically produced sesame oil has been a tradition for centuries. About 65 percent of the annual US sesame crop is processed into oil and 35 percent is used in food.

Varieties

There are many variations in the colour of sesame oil: cold-pressed sesame oil is pale yellow, while Indian sesame oil (gingelly or til oil) is golden, and East Asian sesame oils are commonly a dark brown colour. This dark colour and flavour are derived from roasted/toasted sesame seeds. Cold pressed sesame oil has a different flavour than the toasted oil, since it is produced directly from raw, rather than toasted, seeds.

Sesame oil is traded in any of the forms described above: Cold-pressed sesame oil is available in Western health shops. Unroasted (but not necessarily cold pressed) sesame oil is commonly used for cooking in South India, the Middle East, halal markets and East Asian countries.

Nutrients

The only essential nutrient having significant content in sesame oil is vitamin K, providing 17% of the Daily Value per 100 grams (ml) consumed supplying 884 calories (table). For fats, sesame oil is approximately equal in monounsaturated (oleic acid) and polyunsaturated (linoleic acid) fats, totaling together 80% of the fat content (above table). The remaining oil content is primarily the saturated fat, palmitic acid (about 9% of total, table).

Cooking

One type of sesame oil, a pale yellow liquid with a pleasant grain-like odor and somewhat nutty taste is used as frying oil. A second type of oil, amber-colored and aromatic, is made from pressed and toasted sesame seeds. Although popular in ethnic cooking, it is not suitable as a cooking oil because it burns readily. Instead, amber sesame oil is normally added as a flavoring agent in the final stages of cooking.

Despite sesame oil's high proportion (41%) of polyunsaturated (Omega-6) fatty acids, it is least prone, among cooking oils with high smoke points, to turn rancid when kept in the open. This is due to the natural antioxidants, such as sesamol, present in the oil.

Light sesame oil has a high smoke point and is suitable for deep-frying, while dark sesame oil (from roasted sesame seeds) has a slightly lower smoke point and is unsuitable for deep-frying. Instead it can be used for the stir frying of meats or vegetables, sautéing, or for the making of an omelette.

Sesame oil is most popular in Asia, especially in Korea, China, and the South Indian states of Karnataka, Andhra Pradesh, and Tamil Nadu, where its widespread use is similar to that of olive oil in the Mediterranean.

Traditional uses

In Ayurvedic medicine, sesame oil (til tel) is used for massaging as it is believed to rid the body of heat due to its viscous nature upon rubbing. It is also used for hair and scalp massage. It is also used in many cosmetic applications, including as a carrier oil.

Industrial uses

In industry, sesame oil may be used as

Low grade oil is used locally in soaps, paints, lubricants, and illuminants.

Allergy

As with numerous seed and nut foods, sesame oil may produce an allergic reaction, although the incidence of this effect is rare at approximately 0.1% of the population. Reports of sesame allergy are growing in developed countries during the 21st century, with the allergic mechanism from oil exposure expressed as contact dermatitis, possibly resulting from hypersensitivity to lignin-like compounds.