The selection of a preservative for a formulation is undoubtedly one of the most important, yet most controversial, aspects one can make. With so much choice in preservatives available, and so much misinformation on the internet, how does a formulator make the Perfect Preservative selection?

There is no single preservative that will suit all formulation types and company/product philosophies or product types. Technically, any preservative that is used within limits as specified by regulators in a particular region, and where suited to the product type and end consumer, is suitable for selection. Despite popular (yet misinformed) reports on the internet, preservatives when used within limits specified by the regulators are considered ‘safe’ and suitable for use. So just how does a formulator make the best, if not the Perfect, preservative selection? There are some key elements that need to be considered:

Preservative selection step #1: Company/product philosophy

The first selection step a formulator needs to make is based on the company and/or product philosophies, particularly if there are claims being made about ‘natural’, or ‘avoiding’ the use of certain ingredients and/or if Organic certification (or other certification, for that matter), is required. If a company specifically requests the ‘avoidance’ of certain materials, then preservatives containing those materials must be specifically avoided. If a company is after certification, then only preservatives that comply with the Certifier’s requirements may be selected. As a first step in preservative selection, company/product philosophy and the specific use or avoidance of certain ingredients obviously narrows the choice of preservatives that can be used depending on the selection criteria specified.

Preservative selection step #2: Regulatory considerations

To be used in a personal care product, preservatives must be permitted in the countries in which the product will be sold, and be used within any limits or conditions of use specified. For example, most preservatives have very specific ‘limits’ on addition, and can only be used within the limits specified. Other preservatives may have very specific conditions of use, for example, in wash off products only, or not on mucous membranes. In such cases, conditions of use must be adhered to, to ensure regulatory compliance of the finished product. Limits and conditions of use imposed by regulators have generally been set based on evaluations of safety; so using preservatives in compliance with the regulations is not only a legal requirement but also an important safety consideration to ensure ‘safety when used as directed’ of a finished product.

Preservative selection step #3: Product form

The form of the product will be the next biggest selection criteria, which can impact on preservative selection based on:

• Finished product transparency required (or in the case of emulsions, this may not be important at all!)
• Dispersibility/solubility of the preservative: ensuring a preservative can be easily and homogenously distributed is crucial to ensure a product is adequately preserved in all areas of a large vat!
• Chemical nature of the product: some preservatives are particularly not suited to charged (anionic or cationic) environments while others may work better in these mediums
• Free water content and Microbial Risk Classification (MRC) of materials used in the formulation: materials with higher risk ingredients will need stronger acting preservatives; this does not mean one should ‘over-preserve’ a product, but that careful selection needs to be made to ensure broad spectrum coverage and synergy of blends used to ensure adequate microbial protection of the finished product

Preservative selection step #4: pH

Finally, and just as importantly, the pH of the finished product is essential to be considered. This includes not just the pH of the finished product when it is manufactured, but must also allow for pH drift over the shelf life of the product. The pH of a product containing water WILL move over its shelf life. It is quite typical for the pH of a finished product to move +/- 10% over its shelf life; sometimes this drift can be up to +/- 20%! Selecting a preservative with a limited pH range of compatibility could leave your product un-preserved should a large pH drift occur – so when selecting your preservative, make sure you consider a potential pH drift of AT LEAST +/-10%, if not a little more, to ensure adequate efficacy of the preservative over the shelf life of the product.

Want to learn how to make the Perfect Preservative Selection?

IPCS has full units with details on Microbial testing, control and GMP as well as detailed training on Preservative selection including Preservatives tables (both natural and synthetic) for easy, confident selection purposes and help you find YOUR formulas Perfect Preservative. Contact us direct to find out about enrolling in these specific units or our full training programs: info@personalcarescience.com.au