Sake may not be the first thing that comes to mind when thinking about skincare, however, this Japanese rice wine is responsible for one of the most popular ingredients in Asian beauty products: Kojic Acid!
Kojic acid is a by-product of fermenting the malting rice used to make sake, and was originally found in several species of mushrooms. The name, Kojic, is Japanese and comes from “koji” which means “culture of aspergillus oryzae (rice)”. The appearance of kojic acid produced from the fermentation process ranges from clear, off-white to pale yellow crystals.
This acid is generally used as a preservative booster and chelator. Chelating agents bind up trace metal ion contaminants in your water-containing cosmetic, thus keeping the product microbe-free for longer. They are not preservatives in their own right, they just help to kill microbes by starving them. (For more on this and another favorite chelator, check out this blog).
Kojic Acid is also very effective in helping skin appear even in color, making it a very desirable ingredient. It is also a popular part of many products targeted towards aging skin.
How to Use Kojic Acid in Skin Care
There are a few important things to know when formulating with Kojic Acid.
Kojic acid is soluble in water, ketones, and alcohols
Melting point: 305 – 311 Fahrenheit
Use Level: 1-3%
Kojic Acid may have potential color instability problems if not handled properly. It’s very important to use Deionized Water. The potential color issue of kojic acid can be alleviated by keeping metal ion content as low as possible, especially iron which is why using Deionized Water is so important. Kojic acid is a chelating agent for many metal ions, especially for iron. In fact, the reaction of kojic acid with iron is used as a quantitative analytical method to determine the iron level in water. Any cosmetic formulation changes color instantly if kojic acid is added to the water that contains iron. Therefore, iron content should be kept to a minimum. If you are still having difficulty, you can add Na2-EDTA to the water before any other ingredients are added.
- Incorporate into the formulation 0.05-0.1% ascorbic acid or 0.1-0.5% sodium bisulfite to stabilize the
formation. - Only use stainless steel or glass lined containers when using Kojic Acid.
- Heat and air contact should also be avoided as much as possible because it accelerates the oxidation of kojic acid and thus any color changes.