What is it?
Propanediol is a colorless liquid glycol derived from corn that can be used as a renewably sourced alternative to petroleum-derived glycols.
What does it do?
Propanediol was originally introduced into Tom’s products to help form the base for our deodorants without using a petroleum-derived propylene glycol. When combined with sodium stearate (soap), it takes on a form that is more viscous or solid. Once suspended in a gel, the other ingredients in these products can be properly applied in the manner consumers expect.
Because it is a highly pure, food-grade material we have also used it, along with glycerin, in some of our gel toothpastes and mouthwashes to help provide consistency and stability.
How is it made?
Propanediol starts with corn. The harvested kernels are dried and prepared for wet-milling, where the sugar-rich starch is extracted. The dried kernels are then soaked in hot water and mild acid to soften the corn’s shell to release the starch. They are then ground, screened and centrifuged to separate the starch from the protein. Sugar derived from the starch is the raw material for the propanediol. At this point, a microorganism is introduced to the corn sugar for fermentation. Once the fermentation is complete, the propanediol is purified and refined.
Propanediol can also be produced from the petrochemical propylene oxide, as can propylene glycol (a closely related material).
What are the alternatives?
Vegetable glycerin is one propanediol alternative. We launched a deodorant product with this base in 1993, but complaints poured in shortly after the new product hit store shelves. Vegetable glycerin, it would turn out, created an unsatisfactory product. The stick it formed was described as “soft and mushy” and about half our users voiced concerns that the vegetable glycerin actually seemed to facilitate the growth of odor-causing bacteria.
Another alternative to propanediol is propylene glycol. Although these share the same chemical formulas, their chemical structures are different. In addition, propanediol is typically derived from corn, where propylene glycol is typically derived from petrochemicals. In 2014, Tom’s of Maine became the very first deodorant brand to transition its product line from a propylene glycol derived from natural gas to a 100% vegetable derived replacement, since that introduction we have transitioned more of our deodorants to vegetable-derived propylene glycol. We have also expanded the use of propanediol in oral care products where, along with glycerin, it contributes to the consistency and stability of those products.
Is this the right option for me?
Propanediol is considered a safe and appropriate ingredient not just for cosmetic products, but also for ingested food products like certain baked goods. This ingredient has approval from EcoCert™ (an international recognized natural and organic seal) and the Natural Product Association (US based natural personal care certification).
Tom’s of Maine recognizes that no two people are alike, and even with naturally derived ingredients, some individuals may develop an allergic reaction that is unique to them. As with any product, be sure to discontinue use if you experience discomfort or other indications that the product may not be appropriate for your individual body chemistry.