Propylene glycol is a fairly common ingredient used in a wide array of products including food, cosmetics, and pharmaceuticals. The compound is exceptionally versatile when it comes to its myriad of uses which is why the propylene glycol market was valued at USD 3.8 billion in 2019 with estimates of 4.4% growth as it could reach USD 4.7 billion by 2024 (1). Since propylene glycol can be found in so many products, people might wonder if whether it is vegan or not.
Propylene glycol is suitable for vegan diets and lifestyles as it is produced using chemicals that are not derived from animals in any way. It can be found in many non-vegan products, but the compound itself passes the requirements for being classified as vegan.
Propylene glycol is an aliphatic diol that typically presents as a viscous, odorless, colorless liquid. While its chemical structure is denoted as CH3CH(OH)CH2OH, propylene glycol is also known by its official chemical nomenclature propane-1,2-diol (2).
The compound can also be in various forms listed under its family such as monopropylene glycol, dipropylene glycol, and tripropylene glycol.
Propylene glycol is used in food in a wide variety of ways. One major function that propylene is utilized for is as a humectant. Humectants are hygroscopic substances that help products retain moisture. Thus, propylene glycol prevents certain food products from drying out.
Propylene glycol is also used as an anticaking agent, a substance that prevents the different components of food products from sticking together and forming clumps. As a dough strengthener, propylene glycol is also used in baked goods to make them more stable by modifying the starch and the gluten.
The compound is also used in many products as a flavoring agent, particularly as a flavor carrier. Propylene glycol helps preserve the flavors used in the food products and also helps keeps the flavor ingredients dispersed, especially when used in beverages.
The specific chemical properties of propylene glycol also make it an ideal emulsifier. Emulsifiers are substances that keep certain liquids mixed. Substances that are polar opposites (e.g., water and oil) and prefer to remain separated. However, certain food products rely on emulsifiers to keep everything mixed properly to deliver the intended taste and experience to the consumers.
Along with glycerin, propylene glycol is also a principal component in e-cigarette liquids. In this context, the propylene glycol is used to generate the vapor that resembles the smoke. The added propylene glycol also acts as a vehicle for the flavor additives in the e-cigarette liquid and enhances the user experience.
Since propylene glycol does not utilize animal products or derivatives in its production, the compound is suitable for vegans.
People might mistake propylene glycol for another compound with a similar name – propylene glycol fatty acid esters. Both are used in the food industry for various reasons, but propylene glycol fatty acid esters might be non-vegan if it was produced using fatty acids derived from animal sources. While propylene glycol fatty acid esters can be considered a possible gray area, propylene glycol is perfectly fine.
First prepared in 1859, the synthesis of propylene glycol used to rely on the hydrolysis of propylene glycol diacetate. However, the production process of propylene glycol has changed throughout the years and practically all of the propylene glycol produced nowadays uses propylene oxide as the starting material.
The main reaction for propylene glycol production remains the same since it was first prepared – hydrolysis. Essentially reacting with water, manufacturers control several factors such as temperature and pressure to specify what type of propylene glycol is produced (i.e., mono-, di-, and tripropylene glycols). The hydration reactors used can reach up to 120–190°C at pressures up to 2170 kPA.
After the hydration reactions, the products are removed of excess water using evaporators and drying towers. The propylene glycol is further purified using high vacuum distillation.
Due to its functional versatility, propylene glycol can be found in many food products including many packaged food items such as prepackaged coffee, creamers, drink mixes, breakfast foods, desserts, snacks, prepared meals, mixes, seafood/meat breading/marinades/glazes (including pre-marinated ham/ turkey), dried soup or bouillon, and most fast food.
The compound can also be found in some bread (e.g., bread, bagels, rolls, breadsticks, bread mixes), bacon, canned beans, dairy products (e.g., cream cheese, yogurt, sour cream, dips/spreads, cheese, whipped cream), many condiments, and occasional frozen vegetables. It can also be found in artificial flavor extracts and artificial food coloring agents.
Many individuals have expressed concern for the safety of propylene glycol, mainly because the compound is also the main component of certain antifreeze solutions. However, the quality and quantity of propylene glycol used in antifreeze products and food are not the same.
In food products, propylene glycol is generally considered to be safe as certified by various food safety authorities.
The FDA (Food and Drug Administration) approves propylene glycol for human consumption as the compound passes the specifications of the Food Chemicals Codex (3).
According to its FDA certification, propylene glycol has approval for various uses including as an anticaking agent, an antioxidant, a dough strengthener, an emulsifier, a flavor agent, a formulation aid, a humectant, a processing aid, a solvent and vehicle, a stabilizer and thickener, a surface-active agent, and as a texturizer.
The FDA also limits propylene glycol according to good manufacturing practice and at maximum levels in certain products (i.e., 5% for alcoholic beverages, 24% for confections and frostings, 2.5% for frozen dairy products, 97% for seasonings and flavorings, 5% for nuts and nut products, and 2% for all other food products).
The EFSA (European Food Safety Authority) also provides approval for the use of propylene glycol for human consumption. The organization maintains its limit that the acceptable daily intake (ADI) limit of the compound at 25 milligrams per kilogram body weight, a decision first implemented back in 1996 (4).
According to the appropriate safety evaluations, the EFSA finds no evidence that propylene glycol can induce toxicity, genotoxicity, reproductive toxicity, and developmental toxicity when used in moderation.