Toasted sesame oil

What toasted sesame oil is

Toasted sesame oil is the dark, strongly scented oil pressed from sesame seeds that have been roasted first. It runs from amber to brown, It is a seasoning rather than a cooking medium. The oil from raw seeds, which may be cold-pressed, is a pale, light oil that serves for stir-frying and deep-frying; the toasted oil is added at the end of cooking, because it is not suited to high heat.

In China it is zhima you (芝麻油) or xiangyou (香油), in Japan goma abura (ごま油), and in Korea chamgireum (참기름). All three cuisines use it for seasoning and dips. It differs from the light oil pressed from raw seed, from sesame paste such as tahini, which is the ground seed, and from the whole seed itself.

The oldest oilseed

Sesame, Sesamum indicum, is regarded as the oldest oilseed crop known. Charred remains from about 3500 to 3050 BC point to domestication on the Indian subcontinent, and cultivation is documented from about 3000 BC. The place of origin is still argued. Most wild Sesamum species are native to sub-Saharan Africa, which led many scholars to propose an African origin; the richness of cultivated forms in Asia led others to argue for the Indian subcontinent, and charred seed has supported domestication in north-western South Asia in the time of the Indus civilisation. A recent genome study of 927 accessions from 42 countries supports East Africa as the centre of origin, with later movement through the Middle East to South Asia, South-East Asia and East Asia.

The oil trade was old. Sesame was the main oil crop of the Indus Valley, and sesame oil, known as ilu in Sumerian and ellu in Akkadian, was probably exported to Mesopotamia; trade in sesame between Mesopotamia and the subcontinent is placed by 2000 BC. Sesame was grown in ancient Egypt, appears in the Ebers Papyrus of about 1550 BC and was found in the tomb of Tutankhamun, and it was grown and pressed for oil in Urartu by at least 750 BC.

Nothing in the sources reviewed dates the practice of roasting the seed before pressing, so the origin of the toasted oil as a separate product remains unknown.

Growing sesame

Sesame is a fast crop, with a life cycle of 70 to 90 days, about 6,000 seeds per plant and a small genome. It is a plant of tropical and subtropical regions: Africa and Asia grew 96.3 per cent of the world’s seed in 2021. World production was about 6.7 million tonnes in 2024, with India at 0.87 million tonnes, Myanmar 0.72, Sudan 0.63, Nigeria 0.45, Ethiopia 0.44 and Burkina Faso 0.27. In 2023 about 1.2 million tonnes of sesame oil were produced, with India and Myanmar together supplying 34 per cent.

The harvest holds back mass production. The seed capsules open only when fully ripe, so farmers cut the plants by hand and stand them upright to finish ripening. The seed is white or black: lighter seed is common in Europe, the Americas, West Asia and the Indian subcontinent, darker seed mostly comes from China and South-East Asia. Seed holds about 45 to 55 per cent fat, roughly 20 per cent protein and about 0.8 per cent lignans.

Per 100 grams the dried whole seed has 570 kilocalories, 49.7 grams of fat, 23.4 grams of carbohydrate including 11.8 grams of fibre, 17.7 grams of protein and 4.7 grams of water. It is a rich source of several B vitamins and of calcium, iron and magnesium, and it contains phytic acid, which reduces mineral absorption; heating and cooking reduce the phytic acid.

How roasting makes the oil

Making sesame oil begins with washing, drying and crushing the seed, and roasting is the step that decides the character of the oil. Oil is then obtained by mechanical pressing, solvent extraction or hot-water flotation; mechanical pressing is the most widely practised, with low cost, simple equipment and no solvent residue, though it recovers less oil than solvents, and seed moisture, pressing temperature, screw speed and feed rate all change the yield and the amount of lignans kept in the oil.

Roasting works through several reactions at once: the Maillard reaction between sugars and amino acids, sugar degradation, protein denaturation, Strecker degradation and lipid oxidation. Industrial roasting uses 150 to 250 degrees Celsius for 20 to 60 minutes. A laboratory study of 18 combinations, 160 to 210 degrees for 10, 20 or 30 minutes, found that the roasting time mattered more than temperature. After 10 minutes the volatile compounds were mainly pyrazines such as 2,6-diethylpyrazine and alcohols such as 3-hexanol, which give green and nutty aromas. After 20 to 30 minutes heterocyclic compounds, pyrazines, pyridines, thiazoles and furans, dominated at 102.77 to 316.94 micrograms per gram, peaking at 210 degrees for 20 minutes, and phenols such as 2-methoxyphenol appeared, which give smoky and sweet notes but also a pungent off-odour at high concentration. The sensory result was intense roasted and burnt notes. The fatty acid profile of the oil did not change significantly.

Roasting has a ceiling. Roasting too hard or too long can form 5-hydroxymethylfurfural, acrylamide and furan, and hot-air roasting at high temperature for a long time can lose tocopherols and proteins and may produce harman, norharman and benzo(a)pyrene. In the laboratory study, oil from seed roasted at 170 degrees for 10 minutes had the longest oxidation induction time, 48.56 minutes, and 170 degrees for 10 to 20 minutes was the best balance of flavour and stability. Of 56 volatile compounds identified, 30 were key aroma-active compounds, and the sensory panel described the oils as nutty, sweet, roasted, burnt, green and pungent. Those results come from oven-roasted seed extracted with hexane, not from a commercial press, and industrial settings need adjusting. Microwave roasting has been explored as a faster, less wasteful alternative to hot air.

Cold-pressed, roasted or microwaved: how the pre-treatment changes the oil

A comparison of cold-pressed, roasted, microwaved and steam-exploded sesame oils identified 82 aroma compounds. Cold-pressed oil was characterised by aldehydes and phenols, had the simplest aroma and the lowest intensity, and best preserved the heat-sensitive lignans sesamin and sesamolin. Roasted, microwaved and steam-exploded oils had markedly more pyrazines and thiazoles, which carry the roasted and nutty aromas. Microwaved and steam-exploded oils also showed higher total phenolics, sesamol and antioxidant capacity, although some sesamin and sesamolin broke down. Roasting for 20 minutes, microwaving for 8 minutes and steam explosion for 1.5 to 2 minutes gave comparable aroma complexity; over-roasting produced undesirable flavours and lost heat-sensitive nutrients.

A direct comparison with hot air makes the trade-off concrete. Microwaving at 900 watts for 6 to 10 minutes released more gamma-tocopherol into the oil, 349.30 to 408.50 milligrams per kilogram against 304.90 for hot air at 200 degrees for 20 minutes, and produced more aromatic heterocyclic compounds, 42.40 to 125.12 milligrams per kilogram against 25.59. Six minutes gave a stronger roasted-sesame flavour with weaker bitter and burnt notes. The carcinogenic by-products fell: harman reached up to 775.19 nanograms per gram against 1,319.85 for hot air, norharman up to 1,069.99 against 1,168.40, and benzo(a)pyrene up to 1.59 micrograms per kilogram against 1.83. Ten minutes of microwaving went too far, with a strong bitter taste and a burnt flavour.

Pressing interacts with roasting. In a screw press, oil yield from unroasted seed rose with press temperature up to 150 degrees and did not improve at 200. Roasting lowered the yield from a mechanical press, probably through loss of moisture. White seed gave more oil and more sesamin and sesamolin, while black seed was higher in phenolics, antioxidant activity and sesamol. Moderate press temperatures gave the best balance between yield and bioactive compounds.

What is in the oil

Sesame oil is entirely fat. About 80 per cent of the fat is unsaturated, mainly oleic acid, a monounsaturated fat, and linoleic acid, a polyunsaturated one; palmitic acid is the main saturated fat. It holds tocopherols, phytosterols and the lignans sesamin, sesamolin and sesamol, and heating can convert sesamin and sesamolin into sesamol, the lignan credited with the oil’s resistance to rancidity. In the pre-treatment comparison the microwaved and steam-exploded oils were higher in sesamol, and the cold-pressed oil kept more of the original sesamin and sesamolin.

The oil is unusually stable for its composition. Despite its polyunsaturated fat it resists rancidity better than most cooking oils with a high smoke point, and the natural antioxidant sesamol is credited with much of the effect. Roasting is reported to improve oxidative stability, through the products of the Maillard reaction. Even so, light and air shorten its life; storage in amber or opaque bottles and in the refrigerator limits oxidation.

In fermented dishes and sauces

Toasted sesame oil is rarely fermented itself. Its place beside fermented foods is as a finishing seasoning, the roasted aroma that goes on at the end. East Asian cuisines use it for seasoning and dips, and because it does not suit high heat it is added when cooking is nearly done. In South Indian cooking, sesame oil has traditionally been used in curries and with spicy foods.

The oil is one of the forms in which the seed reaches the kitchen: ground to a paste, scattered whole, or pressed to an oil that carries the roasted aroma.

Choosing and keeping it

Choose by colour and scent: a dark amber-to-brown oil with a strong roasted aroma is toasted oil, and the light oil is made from raw seed. Words on a label such as cold-pressed, roasted or microwaved describe the pre-treatment of the seed: cold-pressed oil has the simplest aroma, while roasted oil is built on pyrazines and thiazoles. Some producers refine the oil by solvent extraction, neutralisation and bleaching, mainly for appearance; good seed yields a palatable oil without these steps and many consumers prefer unrefined oil. Buy a quantity you will finish, keep it capped, dark and cool, and use it at the end of cooking.

No storage time is given in the sources reviewed, so none is stated. Burnt notes belong to heavily roasted oil: in the laboratory study they came with 20 to 30 minutes of roasting.

Allergens and dietary context

Sesame is a recognised food allergen. In Europe the sensitisation rate was 4.5 per cent in 2014. In the United States the FASTER Act of 2021 made sesame a major food allergen, and the European Union lists it among 14 allergens that must be labelled; Canada also requires sesame labelling. Prevalence of allergy is estimated at 0.1 to 0.8 per cent in Australia, Canada and the United States and is much higher in the Middle East, and sesame cross-reacts with peanuts, hazelnuts and almonds. The allergens include 2S albumins such as Ses i 1 and the seed oil-body proteins called oleosins. The sources reviewed do not establish how much allergen toasted oil carries, and exposure to the oil can cause contact dermatitis.

Notes

Published figures for the unsaturated share of sesame oil differ by a few percentage points. The roasting study used laboratory conditions and hexane extraction, so its temperatures are a guide to flavour chemistry, not a protocol for pressing. No source reviewed dates the first toasted oil or gives a household shelf life.