574 JOURNAL OF COSMETIC SCIENCE BACK TO BASICS: So You W"ANT TO PRESERVE YOUR EMULSION Introduction David C. Steinberg Steinberg & Associates, Inc. One critical step in developing emulsions is dealing with preserving the product from microbial contamination. You need to look at this to insure that your product complies with regulations and as a form of "insurance" for your product. Nothing will turn a consumer into a non-customer faster, than when she opens the jar of your cream and she finds fuzzy green stuff growing in it! US Regulations The FDA does not require cosmetics ( or topical pharmaceuticals) to be sterile, as they are not applied to sterile surfaces. However, they may not be contaminated with pathogenic microorganisms and total counts must be low. Cosmetics are intended to remain in this condition under reasonable and foreseeable consumer use. Further all cosmetics should be tested for adequacy of preservation, during their development and each batch must be tested before it is released. All recalls for contamination have been made because companies released contaminated products! Preservatives are chemicals added to products to prevent the growth and destroy these contaminants. In theory, we add these to "clean" products to prevent consumer contamination. In reality we use preservatives to correct contamination during the manufacturing of our products along with protection against consumer contaimination. EU Regulations The European Union requires that all cosmetics must have microbiological specifications. All raw materials are also required to have these and both must be part of your Product Information Package (incorrectly referred to as a "dossier"). All products with more than 30 months stability must have a "Period After Opening" symbol with a number and "M" to indicate how many months after the product is open, it will not cause harm to the user. The most common type of harm is due to microbial contamination. Getting Started The most important first step is to see what is the external phase of your emulsion. Most emulsions have water as the external phase but you never can be sure, so check! When water is the external phase, we call these typical products. When water is not the external phase, these are considered atypical. For typical cosmetics you need to run the pH. Atypical products do not really exhibit pH although you can invert this to see what the pH is of your internal phase. Water Activity The next step is to run the water activity (Aw)- This is defined as the vapor pressure of your product at a constant temperature divided by the vapor pressure of pure water at the same temperature. In reality, just measure it. Water activity is a scale of 1. 0 which is pure water to 0. 0 which is bone dry. By knowing the water activity, you can see what will grow in your product. For example, most Gram negative bacteria need a range 0. 91 to 0. 96 for growth, while mold require 0.7 to 0.98 for growth.

2007 ANNUAL SCIENTIFIC SEMINAR 575 To use water activity, you need to remember it only prevents growth, it is not cidal. It is mandatory for you to have good cGMP's in place and employ HACCP. Ingredients that lower water activity include salt and very water-binding molecules like glycols. Now What After you have followed these first steps you should confirm what will grow by seeing what grows in your product. Inoculate like you would do a Preservative Efficacy Tests (PET) and see if your formulation is inherently hostile to anything. Enrichment techniques are recommended. Now you need to see what kind of packaging sales plans to use. Is the packaging such that the consumer cannot contaminate it? Or is the type that is frequently contaminated? Compare a wide mouth jar to a tube with a narrow opening. This is vital in developing what would be an appropriate challenge test for the product and what would be your pass/fail criteria. In deciding what test to use, remember a typical cosmetic is easier to test than atypical products. The CTFA has recently developed methods for atypical cosmetics. Adding Preservatives How you add the preservative(s) is part of the development process. Almost all preservatives degrade under high heat, extreme pH and these conditions are a factor of time that the chemical is exposed to these conditions. Frequently the best procedure for typical cosmetics is to add the preservatives pre-dissolved in a water soluble solvent, below 40 °C. In deciding what preservative(s) to try, you should first see where marketing plans to sell the product. The US is the easiest country with almost no rules concerning preservatives. The EU has a permitted list and Japan has the most restricted. If marketing wants a "global" formulation, than you are limited by the most restricted market. Marketing may also restrict permitted preservatives by saying no parabens, no chlorine, no iodine, no formaldehyde containing chemicals, no ethylene oxide or even no glycols. Finally Run your product stability test and see if your preservative system still works after accelerated aging. If your system passes all of your safety, stability and PET tests, you may want to try these again using lower levels of preservatives. Most time, we over preserve because we lack the time and money to check a second or third time! Conclusion Remember that although it is not the primary purpose of preservatives to destroy contamination during manufacturing, we do need this. The "weaker" the preservative system, the better your cGMP"s!