Natural And Synthetic: Bridging The Gap

This article will outline the development process of new preservative solutions by Sharon Laboratories: Sharon™ Amplify, and SharoSense™ Plus.


 The industry analysis that led the decision to develop two new concepts ‘less is more’ and ‘synthetic-naturals’ as well as review the product efficacy and compatibility for the personal care industry. 


The development project of the preservatives Amplify Line, started from the challenges the personal care industry is facing due to the global trends in preservation. 


The task formulators must address is choosing a preservative solution that will guarantee product safety. The risk of contamination can be influenced by many factors:


 Product type, where is it stored: exposed to moisture, heat or humidity?
INCI: water content, presence of natural extracts, mud, clay, some components create a tougher-to-preserve formula
Packaging: as in general an open jar may increase the contamination risk if compared to a pump or tube  
The products characteristics will define the type of threat to fight: Gram-negative and positive bacteria, yeast or mold. 


So while the need for product safety remains high, the formulators must also take into consideration other aspects: regulatory updates, impact on odor, color, compatibility with other ingredients or even the country’s climate. 


Officially there are many different preservatives to choose from, but professionals in R&D feel there are fewer options. Often, it is the consumer who is perceived as the cause, for wanting ‘free from everything’ product and this generates a call for ‘mild’ systems, to replace classic preservative solutions.


The problem is that mild systems are in fact… mild – too mild. Many of the new preservative solutions are not strong enough to handle the antimicrobial challenge, and there is a risk for microbial contamination. 


When the preservative solution is not strong enough, there are a few actions the manufacturers of finished goods would do. First – to raise the level of use, and that would probably be over 1%. Another option is add additional material: booster, preservative, extract with some antimicrobial activity. One more path is adding a chelating agent, and of course, a combination of all the above. 


However, those steps have implications. Higher levels of use of a preservative can raise regulatory issues as many materials are allowed for use in a specific limit (like phenoxyethanol or benzyl alcohol at 1% maximal limit). In addition, a higher level of use can cause formulation hurdles such as impact on viscosity, stability, odor and more. Further implications come from the end user angle, such as skin sensitivity, and of course, higher cost.


 


Taking a new approach to preservation


Many personal care companies today are dealing with tough-to-preserve products, where they wish to avoid the use of classic reliable preservatives such as parabens, formaldehyde donors and isothiazolinones. Avoiding those drives them to use combinations of a solvent such as phenoxyethanol with a booster such as ethylhexylglycerin or caprylyl glycol, just to find out this solution is not enough for broad spectrum protection against bacteria, yeast and molds and poses a risk of possible contamination. 


Our goal was to offer a new preservative solution that would have strong efficacy, and allow a significantly lower level of use in finished products. In order to achieve this goal, we researched the potential role of cationic catalysis in preservation. 


It is found that a combination of several ingredients known to have a mild antimicrobial profile can be reinforced by the presence of cationic surfactants in a specific low ratio. 


Several molecules with cationic properties were evaluated. Among them didecyldimmonium chloride, polyquaternium2, polyquaternium-80, and others. 


An optimization project was performed in order to evaluate the level of the cationic surfactant needed to enhance different preservative solutions. 


It was proven that the addition of a cationic catalyst in various ratios improved the efficacy of the preservative blend significantly, allowing the level of use in a finished product to be reduced by 50%. 


This is demonstrated in Figure 1 comparing the efficacy of a preservative blend by itself, and with the amplified effect. The efficacy is determined by minimum inhibitory concentration (MIC) which is the lowest concentration of a chemical which prevents growth of a bacterium. 


The MIC help and guide us to determine the level of use of the enhanced blends, as we strive to achieve the lowest MIC possible. For example a commonly used blend of phenoxyethanol with ethylhexylglycerin would normally be used at a level of 1%. Its amplified version would be used at the same product, with a level of use of 0.5%. A successful challenge test result is demonstrated in Figure 2. It is shown that by day 7 the microbial count was already below 10 and remained at that level for the duration of the full 28 days, thus passing USP criteria for category 1 products. Due to the cationic profile of these preservative blends, it was critical to also test its efficacy in a formula with anionic ingredients, common for rinse-off products.


In the optimised blends, we can show strong broad spectrum protection in anionic based products, as can be seen in Table 1 of the challenge test results. This line was developed further to provide a range of option to answer the industry needs: ‘Phenoxyethanol-free’ alternatives based on methyl propane diol is a good example.


The optimisation process is different in every combination. The level of the cationic surfactant that would enhance a blend of phenoxyethanol with ethylhexylglycerin would not be right for another preservative combination. Some preservatives did not demonstrate an amplified effect with the presence of a cationic surfactant. 


The flexibility of this platform allows a global approach, approved and allowed for use in US, EU, Brazil, Japan and China, and are applicable to all applications.



source from https://www.personalcaremagazine.com/