What Type of Lipid Is Triolein?

December 22, 2025 •

3 min read

Triolein, also known as glyceryl trioleate, is a symmetrical triglyceride that constitutes a significant portion of many vegetable oils, most notably olive oil. A lipid is a broad category of naturally occurring molecules that includes fats, oils, and waxes. This article will delve into the specific classification and properties of triolein within the vast world of lipids.

Quick Summary

Triolein is a simple, unsaturated triglyceride, or triacylglycerol, composed of a glycerol backbone esterified with three units of the unsaturated fatty acid oleic acid. It is a liquid at room temperature due to its unsaturated structure and is a major component of olive oil.

Key Points

Triglyceride Classification: Triolein is a type of lipid known as a triglyceride, formed from a glycerol backbone and three fatty acid chains.
Unsaturated Lipid: It is an unsaturated triglyceride because its component fatty acids, oleic acid, contain a carbon-carbon double bond.
Simple Triglyceride: Triolein is a simple triglyceride because all three fatty acid chains attached to the glycerol molecule are identical (all are oleic acid).
Liquid at Room Temperature: Due to the kinks introduced by the unsaturated double bonds, triolein is a liquid at room temperature, classifying it as an oil.
Natural Occurrence: It is a major constituent of many vegetable oils, most notably comprising a significant portion of olive oil.
Cosmetic and Medicinal Uses: Triolein is used as an emollient in cosmetics and is a component of Lorenzo's oil, used in the treatment of a rare genetic disorder.

The Chemical Identity of Triolein

At its core, triolein is a triglyceride, also known as a triacylglycerol. This places it squarely within the class of neutral lipids. To understand this classification fully, one must break down the molecule's composition. A triglyceride is formed through an esterification reaction, where three fatty acid molecules bond to a single glycerol molecule. In the case of triolein, the glycerol backbone is attached to three identical fatty acid chains, specifically oleic acid. This makes it a simple triglyceride, as opposed to a mixed triglyceride which would contain two or three different types of fatty acids.

The Role of Unsaturated Fatty Acids

The most defining characteristic of triolein is its unsaturated nature. Oleic acid, the building block of triolein, is an 18-carbon long monounsaturated fatty acid. The term "unsaturated" refers to the presence of a carbon-carbon double bond within the fatty acid chain. This double bond introduces a 'kink' or bend in the molecule's shape, preventing the chains from packing together as tightly as saturated fatty acid chains. This structural difference is the key reason why triolein exists as a liquid at room temperature, while triglycerides made from saturated fatty acids (like tristearin) are solid. The specific double bond in oleic acid is in the cis configuration, which is the type typically found in natural plant oils and is a factor in its liquidity.

Natural Sources and Applications

Triolein is a natural component of many fats and oils found in plants. Its abundance in olive oil is particularly notable, where it can make up anywhere from 4% to 30% of the oil's composition. The presence of this unsaturated lipid is a major contributor to olive oil's liquid state and its reputed health benefits. Beyond its role in food, triolein has various industrial and biomedical applications.

Common Sources of Triolein

Olive oil: Contains a high percentage of triolein, contributing to its liquid consistency and health properties.
Sunflower oil: Another vegetable oil that contains triolein.
Palm oil: This plant-based oil also contains triolein.
Lorenzo's oil: Triolein is one of the two components of this specialized oil mixture used in the investigational treatment of adrenoleukodystrophy (ALD).

Applications of Triolein

Cosmetics: Used as a skin conditioning agent and emollient, it helps moisturize and protect the skin.
Pharmaceuticals: Its inclusion in Lorenzo's oil demonstrates its use in specific therapeutic contexts.
Research: Serves as a model compound for studying enzyme activities and biochemical processes involving triglycerides.

Comparison Table: Triolein vs. Other Common Triglycerides


Feature	Triolein	Tristearin	Tripalmitin
Fatty Acid	Oleic Acid (18:1, monounsaturated)	Stearic Acid (18:0, saturated)	Palmitic Acid (16:0, saturated)
Saturated/Unsaturated	Unsaturated	Saturated	Saturated
Source	Olive oil, sunflower oil	Animal fats (tallow)	Animal and plant fats
State at Room Temp.	Liquid (Oil)	Solid (Fat)	Solid (Fat)
Reason for State	Cis double bonds prevent tight packing	No double bonds; straight chains pack tightly	No double bonds; straight chains pack tightly

The Importance of the Glycerol Backbone

The glycerol component is the central hub for all triglycerides, including triolein. It is a simple, three-carbon molecule with a hydroxyl ($OH$) group on each carbon. The fatty acids attach to these hydroxyl groups via ester bonds, a crucial linkage that defines the molecule as a triacylglycerol. This basic structure is the foundation of all dietary fats and a key energy storage mechanism for many organisms. The uniformity of the oleic acid chains on the glycerol backbone is what makes triolein a 'simple' lipid rather than a 'mixed' one.

Conclusion

To summarize, the answer to "what type of lipid is triolein?" is that it is a simple, unsaturated triglyceride, or triacylglycerol. Its chemical structure, consisting of a glycerol backbone esterified with three identical oleic acid chains, explains its properties. The unsaturated nature of the oleic acid chains, with their defining double bonds, dictates that triolein is a liquid at room temperature, which is why it is classified as an oil rather than a solid fat. This understanding of triolein's chemical makeup helps clarify its biological functions and its prominent role in plant-based oils.

The Breakdown of Triolein

Classification: Triolein is a triglyceride.
Sub-Classification: It is further categorized as a simple, unsaturated triglyceride.
Building Blocks: It is composed of a glycerol molecule and three oleic acid molecules.
Physical State: Its unsaturated fatty acid chains mean it is a liquid at room temperature, classifying it as an oil.
Common Source: A major component found in olive oil.

Frequently Asked Questions

Triolein is an unsaturated lipid. It is composed of three molecules of oleic acid, which is a monounsaturated fatty acid containing one double bond in its hydrocarbon chain.

As a triglyceride, triolein serves as a high-energy storage compound in organisms. When energy is needed, it can be broken down into glycerol and fatty acids to fuel cellular processes.

A simple triglyceride, like triolein, has three identical fatty acid chains attached to the glycerol backbone. A mixed triglyceride, which is more common in nature, has two or three different types of fatty acid chains.

The unsaturated nature of triolein's oleic acid chains, with their double bonds, prevents the molecules from packing together tightly. This loose packing results in a lower melting point, causing it to be a liquid oil at room temperature.

Olive oil is a particularly rich source of triolein. Triolein is also found in other vegetable oils, such as sunflower and palm oils.

Lorenzo's oil is a specific therapeutic oil mixture used in the treatment of adrenoleukodystrophy (ALD). Triolein is one of its two main components, along with trierucin, designed to help normalize the levels of very-long-chain fatty acids in the blood.

In cosmetics, triolein is utilized as a skin conditioning agent, an emollient, and a viscosity controlling agent. Its moisturizing properties help to soften the skin and create a protective film.