Why Do They Put Propylene Glycol in My Drinks?

Being a chemist, I'm forever reading ingredients labels on the foods I eat and the beverages I drink. I'm much impressed when I've bought something and the label only shows two or three ingredients. It seems when I buy something inexpensive - presumably of lesser quality - the list reads on endlessly. One ingredient I find in some of the beverages is propylene glycol. Another, less frequently used substance in the food industry is the polymeric version of propylene glycol, polypropylene glycol.¹

Now perhaps you've heard of ethylene glycol, aka antifreeze? It's always spooked me that antifreeze kills pets, so when I read that something I'm consuming contains the chemically similar propylene glycol, I had to learn why they put propylene glycol in my drinks? It is also in other food substances and even medications we take.

Simply put, propylene glycol has properties that are useful to the food, drug, and beverage industries. Of course, one can't simply put anything they want into foods and drugs. Not only would it be in poor taste to kill off your customers, it is against the law. How strict are legal standards? Are standards formed only with the consumer in mind? Well, no. They are also formed with the entrepreneur in mind. Whenever money is involved, standards can be tight or they can be slack.

What are some of the good qualities of propylene glycol that make it of interest to industry? Some of the uses are listed by Dow Chemical, here. We will touch lightly on a few of them, beginning with pharmaceutical use, then pet food use, then human food use.

In the pharmaceutical industry, it is used as a non-active ingredient "in oral, topical and injectible drug products."

It is used in the pet-food industry as a solvent, stabilizer, preservative, humectant (moisturizer), dust-control, wetting agent, and (surprise!) it lowers the freezing temperature of the feed. It is also listed as a preventative for ketosis.²

Propylene glycol is used by humans in a number of ways, but to mention a couple of important applications involving consumption, propylene glycol is used as a humectant and stabilizer for baked goods³ and prepared foods and vegetables, and as a solvent for substances such as flavorings and colorings that are not readily soluble on their own.

It ought to be remarked that propylene glycol is general recognized as safe GRAS (except for cats). Curiously, "In countries of the European Union, propylene glycol is not cleared as a general-purpose animal feed additive."⁴

As a chemist and a consumer, I am not up-in-arms over the use of propylene glycol in foods. The government does deem it safe for consumption as it is being used. However, as a realist, I do recognize that many things now in use are not particularly good for me, and it represents an exercise in sound judgment if I consume more foods that are processed as little as possible.

^{1 Polypropylene glycol is used as a de-foaming agent.}

^{2 Description/Definition of Ketosis: UK's National Health Service. "Propylene glycol thus reduces a bad condition resulting sometimes from the breakdown of excessive fats. Animal food wouldn't contain much of that, would it?" (Author's Remark)}

^{3 "So is that why store-bought baked goods seem to stay moist a long time?" (Author's Remark)}

^{4 http://www.dow.com/propyleneglycol/app/petfood.htm}