How Sesame Oil Is Made: From Sesame Seeds to Thai Kitchen Bottle

Sesame oil is made by cleaning ripe sesame seeds, sometimes roasting them, then crushing or pressing them so the oil separates from the solids. The oil is then left to settle and filtered. Roasting before pressing gives dark, nutty toasted sesame oil. Pressing raw seeds gives pale, mild oil. Seeds roasted, pressed and filtered this way produce the oil sold as nam man nga (น้ำมันงา) in Thai markets, from the seed the Thai language calls nga.

What Are Sesame Seeds and Where Does the Oil Come From?

Sesame seeds are the small, flat, teardrop-shaped seeds of the sesame plant. They grow in upright pods along a tall, leafy stem. Each seed is only a few millimetres long and is rich in oil. Commonly cited figures put the oil at roughly half of the seed's weight, which is why sesame has been pressed for oil for thousands of years.

In Thai kitchens you will usually meet two kinds of seed:

White sesame (nga khao) is creamy ivory with a mild, sweet taste. It is the most common source of everyday sesame oil.
Black sesame (nga dam) has a dark, slightly bitter hull and an earthier taste. It appears often in sweets and snacks and is also pressed into oil.

How Is Sesame Harvested Before Oil Extraction?

Sesame harvesting begins when the plants dry and the pods ripen and start to split. On many sesame varieties the pods burst open when fully dry, which is the image behind the phrase \u201copen sesame.\u201d Farmers often cut the stalks before the pods shatter and scatter their seeds.

Cutting: The stalks are cut once the pods are mature.
Drying: The bundles are stood upright or laid out so the pods dry and open.
Threshing: The dried stalks are shaken or beaten so the seeds fall out.
Cleaning: Dust, bits of pod and small stones are sifted and winnowed away.

Clean, dry seeds matter for oil quality. Damp or dirty seeds can spoil and make the finished sesame oil taste stale or musty.

What Are the Steps of Sesame Oil Extraction?

Sesame oil extraction follows a simple sequence: prepare the seeds, crush or press them, then clean the oil. Small traditional mills and large factories follow the same basic idea, but they use different equipment.

Step 1: Preparing the seeds

The cleaned seeds may be soaked and hulled to remove the thin outer skin. This is common when a very light, smooth result is wanted. Many oils, especially traditional ones, are pressed from whole seeds.

Step 2: Roasting, or not

Roasting is the step that decides the oil's colour and smell. To make toasted sesame oil, the seeds are heated until they turn golden to deep brown. The kitchen fills with a warm, popcorn-like, nutty aroma. For untoasted oil the seeds stay raw and pale, so the oil tastes much gentler.

Step 3: Pressing or grinding

Pressing squeezes the oil out of the crushed seeds. There are three main approaches:

Traditional mills: Seeds are ground between stone or wooden parts, sometimes turned by animals or slow motors. The oil seeps out of the thick paste.
Expeller pressing: A metal screw forces the seeds through a narrow barrel. Oil runs out through small gaps, and a dry \u201cpress cake\u201d comes out the other end.
Cold pressing: This is mechanical pressing done with limited heat. It aims to keep the raw seed's light flavour.

Large industrial plants may also use chemical solvents to pull the last oil from the seed cake. That oil is then refined. Labels such as \u201ccold-pressed\u201d or \u201cexpeller-pressed\u201d tell you the oil was obtained mechanically.

Step 4: Settling and filtering

Fresh-pressed sesame oil is cloudy with fine seed particles. The oil is left to stand so the heavy sediment sinks. It is then filtered through cloth, paper or mechanical filters until it runs clear. Some producers bottle lightly filtered oil, which can look slightly hazy.

Step 5: Refining and bottling (for some oils)

Refined sesame oil goes through extra cleaning steps that remove colour, smell and impurities. The result is a clear, nearly neutral oil. Toasted and cold-pressed oils are usually bottled without refining so they keep their character. Dark glass or tins help protect them from light.

How Do You Tell the Types of Sesame Oil Apart?

You can usually identify the type of sesame oil by its colour and smell. Darker oil almost always means roasted seeds and a stronger flavour.

Type	How it is made	Colour and aroma	Best use
Toasted sesame oil	Roasted seeds, pressed and filtered	Amber to deep brown; strong, nutty, roasted smell	A few drops to finish dishes, dressings and dips
Untoasted or cold-pressed sesame oil	Raw seeds, pressed mechanically	Pale gold; mild, faintly seedy smell	Gentle cooking, dressings where a soft flavour is wanted
Refined sesame oil	Pressed or extracted, then refined	Very light and clear; almost no smell	General frying and stir-frying
Black sesame oil	Black seeds, often roasted, then pressed	Dark; deep, earthy, slightly bitter aroma	Specialty dishes and flavouring

Some bottles of toasted oil are blended with a neutral oil to soften the taste. The label will list both oils.

How Is Sesame Oil Used in Thai Cooking?

In Thai cooking, sesame oil is mostly a flavouring oil, not the main frying fat. Everyday Thai frying usually relies on neutral vegetable oils, so a little toasted sesame oil goes a long way. It shows up most in dishes with Thai-Chinese roots.

Marinades: A small splash of sesame oil with soy sauce, garlic and pepper adds a roasted note to meat before grilling or stir-frying.
Soups and noodles: A few drops on top of a clear broth or a bowl of noodles add aroma just before serving.
Dipping sauces and dressings: Stirred into soy-based dips, it adds richness and a glossy sheen.
Stir-fries: Added at the end of cooking, it lifts the smell of vegetables or rice.

Simple tip: Add toasted sesame oil at the end of cooking. Its delicate aroma fades, and it can turn bitter, if it is heated hard for a long time. For high-heat frying, use refined sesame oil or another neutral oil instead.

How Does Sesame Oil Differ from Peanut Oil?

Sesame oil and peanut oil are both pressed from oily seeds, but they behave differently in the kitchen. Toasted sesame oil is strong and dark and is used by the drop as a seasoning. Peanut oil is usually pale with a mild, slightly nutty taste. It is often used in larger amounts for frying. Both seeds are common allergens, so it is worth checking labels when cooking for others.

What Can You Use Instead of Sesame Oil?

No substitute gives exactly the same roasted aroma, but a few options come close in certain dishes:

Toasted sesame seeds: Crush them lightly and sprinkle them over a finished dish. They add nuttiness and crunch, but none of the oil's smooth coating.
Sesame paste or tahini: Whisk a little into dressings or dips. It brings sesame flavour but makes sauces thicker and creamier. Tahini is usually made from lightly roasted or raw seeds, so it tastes milder than toasted oil.
Quick sesame-infused oil: Gently warm a neutral oil with toasted seeds, let it cool, then strain it. This is only a flavoured oil, not true pressed sesame oil. It is milder, and it should be refrigerated and used up soon.
Peanut or neutral oil: This works for cooking, but it has none of the distinctive sesame aroma.

How Should You Store Sesame Oil?

Store sesame oil tightly closed in a cool, dark place, away from the heat of the stove. Light, heat and air slowly make oil go rancid. Fresh sesame oil smells clean and nutty. Spoiled oil smells sharp, stale or paint-like and should be thrown away. If you use sesame oil only occasionally, buy a small bottle so it stays fresh until it is finished.