Glycerin, also known as glycerol or glycerine, is a simple polyol compound with the chemical formula C3H8O3. This colorless, odorless, and sweet-tasting liquid has gained immense popularity in various industries due to its unique properties and versatility.
What is Glycerin?
Glycerin of glycerol is a viscous liquid derived from both natural and synthetic sources. It's a key ingredient in many everyday products, from cosmetics to food to pharmaceuticals, known for its hydrating, lubricating, and sweetening properties.
Clear and odorless, it's non-toxic and safe for consumption. Glycerin naturally occurs as part of the triglycerides found in fats and oils. Its hydrophilic (water-attracting) and lipophilic (fat-attracting) properties makes it an excellent moisturizer and emulsifier.
Glycerin can come from both natural and synthetic sources. For example, vegetable glycerin is derived from plants like palm or soybeans, while synthetic glycerin is produced from petrochemical processes.
Discovery of Glycerin
Glycerin is first discovered in 1779 by the Swedish super-chemist Carl Wilhelm Scheele as he studies the byproducts of soap making. He notices a sweet-tasting substance he initially calls "glycerin."
The name derives from the Greek word "glykys, (glyceros)" meaning sweet. At first it's dismissed as a soap byproduct. In the early 19th century, the commercial production of glycerin begins with the rise of soap and candle-making industries.
As glycerin releases its sweet properties, industries such as pharmaceuticals and cosmetics started to realize its value. Today, glycerin is considered an essential ingredient in many products.
How is Glycerin Created and Sourced?
Thee two main methods for producing glycerin are saponification and biodiesel production.
Saponification:
Glycerin is produced as a byproduct of soap-making. In the soap making process a process fats or oils are combined with an alkali like sodium hydroxide to create soap.
The glycerin remaining after soap has formed can be purified for various uses. Most commercially available glycerin originates from the saponification of fats and oils.
Biodiesel Production:
Glycerin is also obtained as a byproduct during the transesterification process, where vegetable oils or animal fats are converted into biodiesel. Many manufacturers use hydrolysis of plant oils such as coconut or palm oil.
Around 10% of biodiesel production results in glycerin. Additionally, glycerin can be synthetically produced from propylene, a byproduct of fossil fuel refining, although this approach raises concerns over sustainability.
What Are Its Properties?
Hygroscopic
Glycerin draws moisture from the air, making it an excellent humectant in skincare products. It's an effective humectant, keeping products like lotions and creams hydrated. Studies show glycerin can increase moisture content by up to 85%.
Soluble
Glycerin or glycerol readily dissolves in water and alcohol, but not in oils.
Viscous
Its thick texture adds consistency to products, enhancing the feel of food and drinks in the mouth. This can be frustrating for people on weight loss plans or special diets.
Non-toxic and Biodegradable
Glycerin is considered non-toxic, safe for human consumption and topical application. The FDA classifies it as Generally Recognized as Safe (GRAS). It's a common sweetener in food and moisturizer in skincare items. Daily intake limit for glycerin is 100 mg/kg of body weight.
Stability
Glycerin is chemically stable, supporting product efficacy over time.
Glycerol is a food additive and preservative in processed meats, cheeses, dairy drinks, sweet beverages, beer, white wine, cakes, confectionaries, dietetic foods and dried fruits and nuts.
Is Glycerin / Glycerol Vegan?
Glycerin can be vegan and non-vegan, depending on its source. Glycerin derived from plant oils, such as palm, coconut, or soybean, is vegan-friendly. Glycerin sourced from animal fats, less common today, is not considered vegan.
Glycerin sourced from animal fats is used in traditional soap-making methods. With rising demand for vegan and cruelty-free products, glycerin from plants has gained popularity. Vegans are advised to check glycerol sources.
Glycerin Reactions with Other Elements
Glycerin is relatively stable and non-reactive under normal conditions. However, it can react with strong oxidizing agents, and when heated, it can break down and form potentially harmful compounds. Used well it can also form helpful ones.
Acrolein
Subjected to high heat and strong acids, glycerin can undergo dehydration, producing acrolein, a compound noted for its acrid odor. Acrolein is the simplest unsaturated aldehyde, a colorless and highly toxic liquid. The smell of burnt fat is caused by glycerol in the burning fat breaking down into acrolein.
Esterification Reaction
Glycerin can react with fatty acids to form glycerides, esters commonly found in food and cosmetic formulations. Glycerides have many functions in the body including energy storage and production, satiety value, insulation, vitamins, essential fatty acids, flavor and texture.
Does Glycerin Occur Naturally?
Glycerin is found naturally in all living organisms. It forms a crucial component of lipids (fats), appearing as a "backbone" in triglycerides, the main form of fat storage in the body.
It occurs as a byproduct of fat metabolism. In the human body, glycerin is released during the breakdown of triglycerides for energy. Small amounts of glycerin exist in many fruits and vegetables, contributing to their sweetness and moisture retention properties.
Do Microbes Eat or Live in Glycerin?
Glycerin is not a food source for most microbes, as it is a simple alcohol rather than a nutrient-rich substrate. Certain bacteria can metabolize glycerin as a carbon or energy source. It's used in laboratory settings to maintain microbial growth as an indirect nutrition source.
In specific fermentation processes, some bacteria and yeast convert glycerin into other substances such as ethanol. Improper preparation can encourage microbial contamination in products containing glycerin.
Cosmetics, Food, Health and Science
Glycerin has an impressive range of applications across various industries:
Cosmetics: Used as a moisturizer and humectant in skincare and hair care products, glycerin helps maintain skin hydration. Glycerin is prominent in lotions, creams, and serums due to its ability to lock in moisture. It makes skin feel soft and acts as an emollient for a smooth texture.
Food: It acts as sweetener, preservative, and texture-enhancer in foods, helping retain moisture in baked goods and confections. It keeps baked goods moist and is often used in sugar-free products as sugar substitute. Glycerin can replace up to 50% of sugar in some recipes.
Pharmaceuticals: Commonly used as a solvent, sweetening agent, and preservative in cough syrups and other liquid medications. In pharmaceuticals, glycerin stabilizes and preserves medications such as expectorants and ointments. Glycerin is also a low-dose laxative.
Science: Used in laboratory settings to create solutions and media for cell cultures, making it crucial for biological research. In laboratories, glycerin is an important reagent and solvent. Its non-toxic properties make it ideal for experiments and tissue preservation.
Glycerol is used in meat preservation. Only the products sorbic acid and its potassium salts; sodium diacetate, an acetic acid salt; nisin, natamycin and glycerol monocaprylate are legally allowed in meat products in the US and other countries.
Interesting Facts About Glycerin
A byproduct of history: Glycerin’s origin in soap-making paved the way for its large-scale production and usage in numerous industries.
Versatile applications: Glycerin is found in products as diverse as e-liquids for vaping, antifreeze, and even dynamite (as nitroglycerin).
Non-irritating: Because it's non-toxic and often used in medical applications, glycerin is safe and well-tolerated by the skin, making it ideal for sensitive skin formulations.
Hydrophilic Nature: Its moisture-absorbing quality makes glycerin a magical additive in hydrating skin products.
Biodiesel Connection: As a valuable byproduct, glycerin production in biodiesel manufacturing supports renewable energy initiatives.
Non-Allergenic: This property makes glycerin an excellent choice for formulating products intended for sensitive skin.
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