Well, this is interesting. The Koreans have been on this for quite some time in the food world, but only recently has it reached what I affectionately call the skin trade (or the “other skin trade”). I like eating kimchi. Turns out the products of fermentation are bacteriostatic, which means it can be viewed as a preservative. This paper from 1994 explores in some depth the chemical and microbiologic basis. Naturally, there is a patent involved for cosmetic uses.
Crit Rev Food Sci Nutr. 1994;34(2):175-203.
Biochemical, microbiological, and nutritional aspects of kimchi (Korean fermented vegetable products).
Kimchi is a traditional, fermented Korean food that is prepared through a series of processes, including pretreatment of oriental cabbage (or radish), brining, blending with various spices and other ingredients, and fermentation. The characteristics of kimchi differ depending on the kimchi varieties, raw materials used, process, fermentation, and preservation methods. However, kimchi has typical biochemical, nutritional, and organoleptic properties and health-related functions. Kimchi fermentation is initiated by various microorganisms originally present in the raw materials, but the fermentation is gradually dominated by lactic acid bacteria. Numerous physicochemical and biological factors influence the fermentation, growth, and sequential appearance of principal microorganisms involved in the fermentation. Complex biochemical changes occur depending on the environmental conditions before, during, and after fermentation. The most important characteristics are the compositional changes of sugars and vitamins (especially ascorbic acid), formation and accumulation of organic acids, and texture degradation and softening. Nutritionally, kimchi is an important source of vitamins, minerals, dietary fiber, and other nutrients. This review covers in some detail the biochemical, microbiological, and nutritional characteristics of kimchi.
Using leuconostoc (a common bug used in fermentation) in the starter culture. “These results indicate that Leuconostoc citreum IH22 dominates over and retards the growth of other lactic acid bacteria in kimchi, suggesting it can be used as a bacterial starter culture to maintain the quality of kimchi for prolonged periods.”
When you ferment radish root (Chinese daikon type radishes) rather than cabbage, by the way, it is called dongchimi rather than kimchi. See pic at right. No comment on the entymology of that term. Korean translations are often awkward.
Ok, now we have some anti-bug juice. This is why fermentation was big before there was refrigeration. In fact until the late 19th century, very few people drank water because it was typically filled with bugs of all sorts. Instead they drank beer. Everyone: men woman, children, even babies. Part of the brewing includes heating, which kills the bugs. But the products of fermentation are mildly bacteriostatic. Hence, a so-called “natural” preservative. Mind you, I wouldn’t prescribe beer for life threatening sepsis – we have much bigger guns.
Which bring us to the question: why preservatives in cosmetics and skin care items? How do we know if they work? How do we measure such things? Well, it turns out that creams and lotions can be favorable culture media for all sorts of bugs, some not at all friendly. So in order to maintain “purity” and prevent “spoilage” the industry adds chemicals to kill bugs or prevent them from growing. But, there are all sorts of bugs. Bacteria (many types), yeasts, fungi. With an antibiotic, we talk about its spectrum – how many different bugs can it prevent or kill? We also want to measure its killing capacity in terms of how much is needed to keep your skin cream sterile.
Back to the kimchi story. Leuconostoc/radish root ferment filtrate (the INCI name of the ingredient) is nicely bacteriostatic against many (but not all) common pathogenic bacteria, but only weakly so against fungi and yeasts. So, it is not as ‘wide spectrum” as many others (including phenoxyethanol).
Now, a manufacturer of such things (PCAA) has introduced a natural preservative solution that protects personal care products against Gram-positive and Gram-negative bacteria: (INCI: Glycerin (and) Leuconostoc/Radish Root Ferment Filtrate (and) Lonicera Japonica (Honeysuckle) Flower Extract (and) Lonicera Caprifolium (Honeysuckle) Extract (and) Populus Tremuloides Bark Extract (and) and Gluconolactone). By adding these other goodies, they gain a little (not a lot) antifungal, anti-yeast action. The solution has a low pH. The preservative solution is a yellow viscous liquid with a pH 4.9 that is recommended at 0.5–2.5% in hand creams, body creams and lotions, facial products, shampoos and conditioners. The label on this stuff says “Products which are highly prone to mold or yeast growth might need additional fungal protection”. This is interesting: benzoid acid (a natural constituent of honeysuckle, is present at 0.0014%. Seems these things bring their own baggage with them.
Thsis might be a good place to discuss the whole “natural” movement in skin care in general, and cosmetic preservatives in particular. Natural substances are not necessarily any safer or healthier that manmade chemicals. Most of the bad stuff out there comes from nature, along with the good stuff. When you see the term “botanicals” used in skin care marketing, does it make you think of healthy things, or deadly nightshade and arsenic or any of millions of other chemicals not too good for you?
Lately I have seen reference to “plant defense systems” with the idea that plant defensins might work out to be a good preservatives. But we need to be careful, because these selfsame plants may be defending themselves against us! In fact, a friendlier source of defensins might be the human variety. Bugs that live in humans aside, our own natural defense systems are quite friendly from human-to-human. Long ago it was discovered that “extracts of human” (things like blood plasma, which contain a whole panoply of human chemicals) can be lifesaving when transfused from one human to another (assuring no bugs). We see in the laboratories around us at the university, other stem cell scientists working on amazing cures based on the idea of transplanting (your or someone else’s) stem cells into diseased areas of the body. What’s the point? We don’t think of human stuff as natural, when it is far closer to our own “nature” than plants, which we do think of as natural. Off my soapbox.
So, back to kimchi (or dongchimi). Is it effective as a preservative? Yes, but it doesn’t give formulators the kind of assurance they need in terms of killing power (spectrum) so only the brave are trying it out. It is less effective than phenoxyethanol. Now, is it less likely to cause sensitivity than say phenoxyethanol? Here again, many chemicals involved, and sensitivity is a “host” characteristic – so it depends on you, your unique defense system, and perhaps even how much exposure you have had.
I won’t be a smart aleck and suggest you rub kimchi on your skin as a test. I would say if the rest of the skin care formulation is based on solid science, no nonsense, then Leuconostoc/Radish Root Ferment Filtrate as a preservative is worth a trial.
Preservative free (refrigerated) cosmeceuticals, anyone?