Improving preservation in a natural way: COSSMA

Preservatives have a bad reputation, especially among consumers, but are necessary to prolong the shelf life of cosmetic products. Tom Fricke and Petra Schaal explain how their share can be reduced by using natural-based boosters.

Consumers are increasingly demanding healthier and more sustainable products. One recent study¹ found that the demand for natural ingredients for cosmetics is on the rise in Europe with sustainability, ethical sourcing, and natural origin ingredients at the top of consumers’ minds. Another survey² showed that both older consumers and younger generations are seeking for safer and more environmentally friendly products, with 76% of consumers wanting brands to ensure safe ingredients and another 54% concerned about environmental impact.

This shift of the cosmetic industry towards more naturality but also safe and clean formulation is particularly challenging for preservation as, on the one hand natural ingredients tend to have in general a higher initial contamination, and on the other hand, traditional preservatives are usually petro-based. At the same time, the list of accepted preservatives is being increasingly revised and regulated, accompanied with consumers’ scrutiny around preservatives which results in manufacturers defining their own internal blacklist.

Yet, even with minimum quantities of preservatives, formulations must be protected from microbial growth. A reasonable way to achieve this is to use boosters to decrease preservative levels to the minimum quantity needed without compromising performance. Current preservative boosters available on the market are mainly synthetic, limiting the options to design safe cosmetic formula suitable for ecolabels.

The offer of multifunctional boosters derived from renewable raw materials that ensure a good product protection while at the same time increasing the renewable content of the finished formulation appears as the best compromise.

figure 1: Key characteristic of the three preservation boosters indicating renewable carbon index, solubility, and pH range for use, compared to bench-mark. figure: Clariant

Natural-origin boosters

Some boosters are surface active molecules that interact with the membrane of microorganisms, making them more permeable to actual preservative allowing to unleash their full antimicrobial power. There are three different technologies behind these multifunctional preservation boosters³.

Sorbitan Caprylate⁴ is used in various types of formulation. It is obtained from natural-origin raw material, notably palm kernel oil derivatives. It shows an antimicrobial synergism with aromatic alcohols, organic acids, and other preservatives. Up to half of the preservative can be saved in this way. Besides the boosting power, the ingredient is oil-soluble and supports the emulsification of leave-on products or thickening of rinse-off formulations⁵; pH range application is between 4 and 8.

The chemical structure of Caprylyl Glyceryl Ether6, active between pH 2 to 12, is very similar to Ethylhexylglycerin, however it has a straight C8-chain compared to the branched chain of Ethylhexylglycerin. This small difference in the molecular structure enables a production pathway using fully renewable feedstocks.

A switch to natural alternatives from synthetic preservative boosters often comes with a loss of performance, and formulators are satisfied if natural alternatives show the same performance as established synthetic standards. The multifunctional ingredient actually outperforms Ethylhexylglycerin and the performance benefits are particularly evident when considering yeast and molds, avoiding an increase in preservative use to overcome the proliferation of those specific micro-organisms, which would ultimately impact the RCI (Renewable Carbon Index) of the finished product.

This ingredient can preserve with only one third the amount of booster required compared to Ethylhexyl-glycerin, reducing the impact on product viscosity. Also, it is a pure, oil-soluble, medium-spreading emollient that is easy to add to all kinds of emulsions and oil formulations and makes it possible to decrease cosmetic emollients in the formulation. A sensorial evaluation of a simple emulsion showed that the substitution of 1% caprylic/capric triglyceride improves the spreadability and wetting properties of the formulation and provides a less greasy, lighter emulsion⁷.

Capryloyl/Caproyl Anhydro Glucamide⁸ is an aqueous cyclic glucamide derived from corn and RSPO MB certified palm kernel oil. It gives quite some flexibility in working with the ingredient due to the high water-solubility, a good pH stability between 3.5 and 9 and its solubilising effects. It can be used as preservation support in almost all cosmetic formulations without any additional solubiliser needed.

Also, it can act as a solubiliser for oils and fragrances. Essential oils are widely used in cosmetics and solubilisers are necessary to incorporate them into the final product. In an initial study there were selected three difficult to solubilise essential oils: Orange, Peppermint and Geranium oil. The test systems consist of water, solubiliser, oil, a preservative and pH adjustant. The ingredient was compared to three other natural solubiliser in the ratio 10:1 solubiliser:oil. It is able to solubilise all oils leading to clear solutions. The performance is similar or even better compared to benchmark natural solubilisers. In addition, it was shown that the solubilisation works at a broad pH range between 4-99.