Updated on 18 July 2024 by: Yeo Yu Teng
What is it | Types of glycerine | How is it made | Uses | Is it safe | Palm oil to refined glycerine | Largest glycerine refining unit
Is glycerine an explosive like nitroglycerin? Not at all. This unassuming yet incredibly versatile ingredient works behind the scenes in countless products you use every day, from keeping your skin hydrated to sweetening your snacks and even aiding in medical treatments. But what exactly is glycerine, and why is it so widely used? In this guide, we’ll explore the wonders of glycerine and uncover its origins and range of applications.
What Is Glycerine?
Glycerine is a natural compound derived from vegetable oils or animal fats. Despite coming from fats, it’s not oily at all. It’s a colorless, clear liquid with a syrupy consistency. While glycerine doesn’t have a distinct smell, it’s pretty sweet when tasted.
For science enthusiasts, glycerine’s chemical formula is C3H8O3. While its chemical structure categorizes it as a sugar alcohol or polyol, it doesn’t have intoxicating effects like the ethanol in wines and beers.
One key characteristic of glycerine is its ability to function as a humectant, meaning it attracts water from its surroundings. This property, due to the three hydroxyl (-OH) groups in its structure, makes glycerine an effective moisturizer and preservative.
The names glycerine or glycerine can be misleading because the “ine” suffix often refers to an amine, which has the -NH2 functional group. The name glycerol is more accurate as the “ol” denotes an alcohol.
What Are the Types of Glycerine?
There are two types of glycerine: natural and synthetic.
Natural glycerine can be derived from vegetable oil crops like palm, coconut, rapeseed, and soy, making it vegan. It can also come from animal fats, most commonly beef or mutton fat.
Synthetic glycerine is made from petroleum-based propylene. It has the same chemical composition as natural glycerine. Sometimes, synthetic glycerine can be confused with propylene glycol as both come from propylene. However, glycol has only two hydroxyl (-OH) groups compared to the three in glycerine.
How Is Glycerine Made?
Glycerine is obtained from triglycerides, which are the main components of body fat in humans and animals, as well as vegetable oils. Triglycerides are esters where three fatty acid chains are bonded to one glycerol molecule. That’s why we have to “free up” the glycerol from the fatty acid chains if we want to get glycerine.
The story of glycerine begins in 1779 [1]. A Swedish chemist named Carl Wilhelm Scheele was heating olive oil together with another chemical containing lead when he accidentally discovered glycerine. He then reported his findings and the glycerine production process in 1783. Today, we can produce crude glycerine in three ways: hydrolysis, saponification, and transesterification. Crude glycerine is then distilled and bleached in distillation plants to refined glycerine.
Hydrolysis
When oils are strongly heated with water, the bonds between the fatty acids and glycerol break, producing a mixture of free fatty acids and crude glycerine. We call this process hydrolysis, which means splitting with water.
Saponification
In the past, glycerine was commonly produced as a by-product of making tallow soaps through a process called saponification, also known as alkaline hydrolysis. This process involves heating cow or sheep fat with a strong alkali solution like sodium hydroxide. Saponification combines hydrolysis and neutralization.
Here’s how it works: during hydrolysis, the heat and water cause the fat to split into crude glycerine and free fatty acids. Then, the alkali neutralizes the fatty acids, forming a soap known as fatty acid metal salt.
Transesterification
In the past, saponification and hydrolysis were the primary methods for producing glycerine. However, in 2004, the glycerine market experienced a significant shift with the rapid growth of the biodiesel industry, where glycerine is a by-product. Today, approximately 70% of the world’s glycerine supply comes from biodiesel production [2].
In biodiesel production, oils and fats are heated with an alcohol like methanol and a catalyst to create biodiesel and crude glycerine. This process, called transesterification, transforms triglyceride esters into another type of ester – fatty acid methyl esters, which is also called biodiesel. And in the meantime, crude glycerine is produced as a by-product.
What Is Glycerine Used For?
Glycerine’s versatility is evident in its wide range of applications across different industries. Here are some of its primary uses:
Food and Beverage
Sweetener for Low-Sugar Food
Glycerine is about 60% as sweet as cane sugar, making it a great alternative ingredient in food [3]. Different regions have their own ways of calculating calories. In the European Union, glycerine is classified as a polyol and labeled as having 2.4 calories per gram (kcal/g), or 10 kilojoules per gram (kJ/g) according to Annex XIV of Regulation (EU) 1169/2011 [4].
Glycerine also has a lower Glycemic Index (GI) than regular sugar. This means it causes a smaller spike in blood sugar levels, making glycerine an excellent sweetener for low-sugar foods.
Preservative to Improve Shelf-Life
Glycerine also works as a natural preservative, extending the shelf life of bread, cakes, cookies, and other baked goods. It does this by attracting and binding free moisture in food, reducing the amount available for microorganisms like bacteria and mold to thrive.
Texture and Flavor Enhancer
Glycerine enhances the texture of food, giving it a smooth feel. It acts as a solvent for flavors and food colorings in soft drinks and confections and as a humectant in dried fruits, energy bars, candies, and cakes.
Cosmetics, Skincare, and Personal Care
Humectant and Emollient
Glycerine is a key ingredient in moisturizers, lotions, serums, body washes, and many other skincare products. As a humectant, it attracts water from the air, binds it to the skin, and keeps it hydrated.
Our skin is composed of dead cells with natural lipids in between, just like a wall of bricks and cement. They form a barrier that prevents moisture loss. When this barrier is disrupted, skin can become dry and chapped. Glycerine’s emollient properties help soften and smooth rough skin.
Moisturizer for Anti-Aging Treatments
Glycerine can penetrate the skin, increase the water volume between cells, and give the skin a fuller, firmer look. This can reduce the appearance of fine lines and wrinkles, making glycerine a potent anti-aging ingredient. It’s also well-tolerated and suitable for all skin types, easily fitting into any skincare routine.
Pharmaceuticals
More Palatable Medication
Glycerine’s soothing and lubricating properties make it useful in cough syrups and tablets to prevent throat irritation and make medicine more palatable. It also makes pills easier to swallow and serves as a solvent and preservative in various pharmaceutical formulations.
Wound Care
If you’ve ever dressed a scrape or burn with gauze, you know how painful it can be to remove. Hydrogels, which are 90% water and commonly contain glycerine, don’t stick to wounds. These dressings keep wounds warm and moist, promoting faster healing without irritating the tissue.
Industrial Applications
Anti-Freeze
Glycerine’s freezing point is unique because it doesn’t have a fixed temperature at which it solidifies. When mixed with water in specific concentrations, its freezing point can be lower than zero degrees Celsius [5]. This is why glycerine is used as an anti-freeze to clear ice from driveways and airplane runways. It’s also used in vehicle engines to prevent freezing in winter, protect against corrosion, aid heat transfer, and prevent rust and scale buildup.
Is Glycerine Safe to Use?
The United States Food and Drug Administration (FDA) states that glycerine is “generally recognized as safe when used in accordance with good manufacturing practice” [6]. While glycerine is usually safe, on extremely rare occasions, it may cause allergic reactions in some people [7]. If you notice redness, itching, or a rash after using a product with glycerine, stop using it right away. You might want to visit a doctor for an allergy test to confirm if glycerine was indeed the culprit. Also, try switching to a glycerine-free alternative, and always check product labels carefully.
How Is Refined Glycerine Made From Palm Oil?
Palm oil can be used to obtain refined glycerine. The journey starts in the plantations where the fruits of oil palms, or fresh fruit bunches, are harvested. They are then processed in the mills to produce crude palm oil (CPO) and crude palm kernel oil (CPKO).
From here, we can get crude glycerine in three ways:
1. Hydrolysis of CPKO yields crude glycerine and palm kernel fatty acids.
2. Hydrolysis of CPO produces crude glycerine and palm oil fatty acids, or palm fatty acid distillates (PFAD).
3. Transesterification of refined, deodorized, and bleached (RBD) palm oil results in crude glycerine and fatty acid methyl esters (FAME), which is the process of manufacturing biodiesel.
This crude glycerine is further refined through distillation and bleaching to achieve refined glycerine with high purity.
Dutch Glycerine Refinery
Aside from our glycerine distillation plants in Indonesia, we operate a refining unit at the Delfzijl Chemical Park in the Netherlands, providing top-quality production and logistical access to major European markets.
References:
[1]:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4415886/#R17
[2]:https://discover.univarsolutions.com/blog/glycerin-insight-production-and-market-updates/
[3]:https://foodinsight.org/what-is-glycerin/
[4]:https://polyols-eu.org/legislation/food/
[5]:https://www.engineeringtoolbox.com/glycerine-boiling-freezing-points-d_1590.html
[7]:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4810294/
