Optimizing Formula Preservation

By: Eric S. Abrutyn, TPC2 Advisors Ltd.

Posted: February 26, 2010, from the March 2010 issue of Cosmetics & Toiletries.

An important consideration in the development of personal care products is the control of microorganism contamination. To ensure that a consumer-ready product is safe, an appropriate preservation strategy must be established for the development, manufacture and packaging of the formula, thus eliminating unacceptable levels of organisms such as pathogenic bacteria, fungi and mold that could grow and pose a health hazard to the consumer.

Key considerations for microorganism exclusion¹ throughout a product’s life cycle include:

• Creating a hostile environment for growth, which involves formula optimization and preservative compatibility;
• Combining preservatives for broad-spectrum benefits;
• Using contamination-free raw materials;
• Sanitizing process equipment;
• Effectively designing packaging to protect the formula and ensure closure as well as a protective barrier, especially during use; Adjusting the process temperature and duration, to control waterborne contamination; and
• Using microbiologically acceptable process water.

It is also important to establish an appropriate written good manufacturing procedure (GMP) protocol for raw material specifications, storage and handling; contamination-free water; and sanitization of equipment—including internal safeguards and aseptic manufacturing operating procedures. An appropriate GMP protocol would include such aspects as:

• Appropriate raw material storage and handling;
• Raw material sampling plans and techniques that minimize contamination;
• Microbiological testing of raw ingredients and process water to assure quality;
• Written microbiological specifications for raw ingredients, processed ingredients and finished goods;
• Written procedures and documentation for cleaning and sanitizing all processing and filling equipment;
• Environmental air sampling in processing and filling areas to ensure good air quality; and
• Packaging component storage control to reduce any risk of microbial contamination.

To control contamination, the adequate cleaning of all areas of equipment prior to sanitization is an important first step. Cleaning in place (CIP) systems should be used wherever possible to facilitate a sterile environment prior to processing commencement. Also, high quality water should also be used to rinse cleansing ingredients from the equipment—this applies in the laboratory as well, to eliminate contamination that could produce a negative micro-test of prototype samples under evaluation. Sanitization should include steam heat (water above 100°C) and germicidal products (e.g., chlorine, cationic surfactants and alcohol).

Optimizing Preservation
In order to optimize the preservation of a personal care product, the preservative system should provide broad-spectrum activity, efficacy at low concentrations—i.e., the minimum inhibitory concentration (MIC)—and act at optimum pH levels. In addition, it should be soluble in both water and oil phases.