Glycerin and Its Many Uses in Both Food and Non-Food Industry

Introduction

 

Despite sounding like a chemical you should stay away from, glycerin is virtually non-toxic to both human health and the environment. This is because glycerin naturally occurs in food items, both as fat and as fermentation material.

Glycerin is a trihydric alcohol that is transparent, almost colorless, odorless, and viscous in its natural form. Its unusual combination of physical and chemical properties makes it highly versatile for various food applications. In addition, the composition of glycerin allows it to be easily compatibility with a wide range of substances.

This water-soluble substance can behave as an alcohol, but it is also stable in most conditions. Its main uses cover various categories, ranging from food applications to urethane foams. Some people choose glycerin as a material because of its physical form, while others prefer it because of its chemical properties.

Glycerin is a fantastic substance with more than 1,500 recognized applications. Throughout the world, glycerin consumption is projected to be between 1.1 and 1.2 billion pounds each year, and this is predicted to grow as less developed countries industrialize.

What is Glycerin?

 

Glycerin, also known as glycerol, is a form of simple carbohydrate known as a sugar alcohol or polyol compound. It also appears as a colorless or brownish liquid that is odorless and viscous, with a sweet flavor and no toxicity. Glycerin is flammable, although it may take some effort to burn.

A byproduct of the alcoholic breakdown of sugars, this substance is produced spontaneously. However, it is now manufactured in smaller amounts by the hydrolysis of fats and oils, as well as by the fermentation of yeast, sugar, or starch.

It is commonly used in FDA-approved wound treatments and can be utilized as an important marker to assess liver disease due to its antimicrobial and antiviral properties. Glycerin has also been used in the food industry as a sweetener, and as a humectant in pharmaceutical formulations.

Brief History about Glycerin

 

The chemical structure and functionalities of glycerin were discovered by accident in 1779 by K. W. Scheele. The Swedish chemist was heating an olive oil and litharge (lead monoxide) mixture until he referred to glycerin as the “sweet principle of fat.”

Later, Scheele discovered that other metals and glycerides undergo the same chemical reaction as glycerin. This method of preparation, which was published in the ‘Transactions of the Royal Academy of Sweden’ in 1783, was used to commercially manufacture glycerin.

Glycerin was not commercially or industrially significant until Alfred Nobel invented dynamite in 1866. Before this, he spent two decades in experimentation. Nobel’s discovery successfully stabilized trinitroglycerin, a highly explosive substance, through kieselguhr absorption. This allowed for safe handling and transportation. Due to the invention of dynamite, glycerin started to have a huge impact on economic growth.

What are the Properties of Glycerin?

 

Glycerin has a unique set of physical properties. First, its chemical reactivity and flexibility make it one of the fundamental building blocks of the chemical industry. It is also used in vast amounts for non-chemical applications and can act as a plasticizer, humectant, solvent, bodying agent, lubricant, sweetener, and so on.

Hygroscopicity

 

Glycerin has the potential to attract and retain moisture from the environment. This function also serves as the foundation for its use as a humectant and a conditioning agent, as both glycerin and water behave as plasticizers. This provides the perfect softness, consistency, and creaminess, as well as prolonged shelf life, to the products.

Low Volatility

 

This relates to the low vapor pressure needed for the permanent presence of glycerin in products. In glycerin’s potency as a humectant, low volatility is directly related to hygroscopicity. Glycerin is nonvolatile at standard usage temperatures, but temperature variations between 0°C and 70°C may have little impact on the vapor pressure of glycerin solutions.

Glycerin’s vapor pressure is lower than its molecular weight. Alcohols, water, and other polar compounds contribute to its low pressure as a function of molecular interaction. Its ability to survive in materials is essential as vast areas are exposed for extended periods of time. Such factors can cause a substantial loss of volatile humectants, which is most common in films and fibers.

Direct Plasticizing Effect

 

Many glycerin applications produce a direct plasticizing effect. This is because it serves as a humectant-plasticizer when it works together with water to encourage softness and stability. It also keeps materials from drying out.

Glycerin can be used for personal goods such as topical creams, lotions, tablets, and dentifrices, edibles such as sweets and cough drops, cigarette smoke, and manufacturing items such as cellophane, paper products, cork and gasket additives, glues, textiles, and printing supplies.

The plasticizing property of glycerin is not limited by its ability to retain water. For instances where there is little to no water present, glycerin can still play a direct plasticizing role.

 

Solvent Power and Solubility

 

Glycerin is considered as one of the most useful compounding additives due to its solvent strength and solubility. Aside from serving as a good solvent for active components in a solution, glycerin’s simple compatibility with many other compounds provides the manufacturers or formulators with a diverse range of additives.

It has solubility properties identical to water and basic aliphatic alcohols due to its hydroxyl groups. Glycerin is an excellent solvent for a wide range of organic compounds, chemical formulations, and flavor extracts and is used to create extremely condensed solutions of many compounds. The chemicals that are more soluble in glycerin than in water include iodine, bromine, tannin, alkaloids, thymol, phenol, mercuric chloride, and boric acids.

 

Miscibility

 

Glycerin is completely miscible in methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and secondary butyl alcohol. It also forms a homogenous mixture with tertiary amyl alcohol, ethylene glycol, propylene glycol, trimethylene glycol, phenol, and ethylene glycol monomethyl ether.

Glycerin is 5% by weight soluble in acetone and 9% soluble in ethyl acetate. It is also only slightly soluble in dioxane and ethyl. However, it is practically insoluble in higher alcohols, fatty oils, hydrocarbons, and chlorinated solvents like hexane, benzene, and chloroform. Hydroxyl and amine groups are added to the composition of glycerin to improve its miscibility for aliphatic and aromatic hydrocarbons.

 

Compatibility

 

Glycerin can behave harmoniously with other materials due to its associated properties of high solvent power, solubility, miscibility, and stability. Long use and analytical studies have proven its compatibility with a wide variety of other materials. It has also been demonstrated to be a highly compatible substance, especially in cosmetic and pharmaceutical products that may contain a range of ingredients with varying chemical structures and properties.

Under normal conditions of use or storage, pure glycerin is stable to atmospheric oxygen. However, at higher temperatures, iron and copper catalysts can promote oxidation. As a result, without the use of inhibitors, handling or storing glycerin solutions in iron or copper-containing vessels should be avoided.

 

High Viscosity

 

This is one of the most distinguishing features of glycerin because of its relevance in various mechanical applications such as hydraulic fluid and laboratory tests of fluid flow dynamics. It is also used in viscosimeter calibrations where aqueous solutions of glycerin are used as standards.

The most common industrial use for glycerin based on its viscosity is as a thickening or bodying agent in liquid formulations, syrups, emulsions, and gels. Glycerin is a viscous substance with 100% saturation at natural temperatures, allowing it to be used across various levels of viscosities without crystallization problems.

Similarly, condensed glycerin solutions appear to cool down as high-viscosity fluids at low temperatures. As glycerin cools down, the viscosity increases slowly at first, then gradually until it reaches -89°C and the substance becomes glassy.

 

Bodying Agent

 

The amount of glycerin applied or its viscosity in a pure state will not necessarily be equal to the amount of glycerin used as a bodying agent. Other ingredients present in the mixture may also be exerting an effect.

The effect of glycerin, for example, the viscosity of a liquid cream is likely to be proportional to the volume applied. It will also rise gradually with additives. However, in the case of a semisolid cream, the addition of glycerin can increase the body up to a certain concentration, causing the viscosity to decrease further.

 

Easy to Use

 

Glycerin is easy to use since it is a liquid at high concentrations and at different temperatures. It also does not form the undesirable crystallization that degrades the appearance of a substance at room temperature. For example, if glycerin is exposed in a dry setting on the threads of a bottle or cap, it will not turn gritty like crystallizing sugar.

 

Anti-Freezing Properties

 

Due to its antifreeze properties, glycerin was the first permanent antifreeze for automotive radiator cooling systems. While ethylene glycol eventually replaced it, combinations of alcohol or glycol and glycerin are still used for this function. Glycerin-water and glycerin-alcohol, on the other hand, are used in certain refrigeration systems and for fast freezing of foods.

Since glycerin is a liquid, it is easy to handle, which is beneficial to many industrial consumers who use glycerin in large quantities. It can be quickly drained from the tank car to the storage tank in some applications and metered to the reactor as required.

It also has the bonus of being able to be assessed by volume or weight. As a result, structures containing other liquid ingredient components will remain completely liquid.

 

Nontoxicity

 

Generations of safe use and supportive evidence have identified glycerin’s nontoxicity as an ingredient in foods and pharmaceuticals. Glycerin appears naturally in foods, both mixed and free, as in fats and fermentation materials like beer and wine.

The human body can consume and metabolize 10 grams of glycerin as glycerides with a daily fat intake of 100 grams. In addition, 10 grams of glycerin have approximately the same nutritional food content as glucose or starch when metabolized.

 

Emollient

 

Glycerin may be applied to all areas of the epidermis and mucous membranes. When diluted to less than 50%, it acts as an emollient and demulcent, especially when used in ointments and lotions.

Water-soluble bases compounded with glycerin are widely used to make preparations for the most susceptible parts of the body. These include antiseptic, genital, oral, analgesic, dermatological burn ointments, and jellies. It is also one of the most commonly used ingredients in pharmaceuticals.

 

Sweet Taste

 

Another advantage of glycerin is its sweet taste, which creates a pleasant sensation in the mouth. According to a scientific study published in 1990, it is 55 to 75% as sweet as sucrose, with the relative sweetness varying based on the concentration tested.

Glycerin, as a sweetening agent, turns certain medical preparations, which may be painful or unenjoyable to swallow, into something more palatable. For example, using glycerin in cough remedies makes the mixture taste better while still calming the mucous membranes.