Cosmetics often provide ideal conditions for microorganism growth due to their high levels of free water and favourable pH. This study emphasizes the importance of maintaining microbiological purity in cosmetic products to ensure both product stability and consumer safety. By utilizing the aWLife instrument, we measure water activity (aW) in various cosmetic formulations, offering predictive insights into the risk of microbial contamination and the effectiveness of preservation systems.
Methods
To assess microbiological risk in cosmetics, we used the aWLife instrument by Steroglass. This device measures the water activity (aW) of cosmetic formulations, a critical parameter influencing microbial growth. The aWLife instrument uses a dew point sensor to provide precise aW measurements, helping to identify formulations susceptible to microbial proliferation.
Results
Our analysis involved testing various cosmetic products, including creams, lotions, and gels, for their aW levels using the aWLife instrument. Products with aW values above 0.60 showed increased susceptibility to microbial growth, requiring enhanced preservative systems. In contrast, products with aW values below 0.60 exhibited significantly reduced microbial growth potential, in line with ISO 29621 and ISO 17516 standards for low-risk cosmetics.
Factors Influencing Water Activity in Cosmetics
aW values depend on several factors:
- Type of raw materials in the formula: humectants, inorganic salts, acids, gelling agents, surfactants. The ability to bind water depends on the chemical characteristics of the molecule.
- Concentration of ingredients: the higher the solute concentration, the lower the aW values.
- Production process: the slow introduction of ingredients into the formula allows the raw materials time to interact with each other, potentially increasing water-binding capacity.
Discussion
The results underscore the importance of monitoring aW in cosmetics to mitigate microbial contamination risks. The aWLife instrument by Steroglass provides reliable, accurate, as well as extremely quickly measurements (in less than 5 minutes), supporting the development of safer cosmetic formulations. Integrating this technology into routine quality control can ensure compliance with EU regulations and protect consumer health.
References
In cosmetic production, there is no explicit regulatory obligation requiring the use of water activity (aW) analyzers to determine the microbial risk of products. However, the use of such instruments is highly recommended and often implied in international standards and guidelines to ensure the microbiological safety of cosmetics. Here is a summary of relevant regulations and standards:
- Regulation (EC) No 1223/2009: This regulation sets safety requirements for cosmetic products in the European Union. While it does not explicitly mention water activity, it requires that products be safe for human use. This implies the need to control various parameters, including water activity, to prevent microbial growth.
- ISO 29621:2017: This standard provides guidelines for microbiological risk assessment in cosmetic products. It includes recommendations on the use of water activity as a criterion to evaluate potential microbial proliferation.
- ISO 16212:2017: This standard specifies methods for determining yeast and mold counts in cosmetic products. While it does not focus exclusively on water activity, its management is crucial for microbiological control.
- ISO 21149:2017: This standard addresses the counting of aerobic mesophilic bacteria in cosmetics. Water activity is a key factor for the growth of these microorganisms, so its control is implicitly required.
- FDA Guidelines for Cosmetics: In the United States, the FDA provides guidelines to ensure the safety of cosmetic products. These guidelines include the need to control water activity to prevent microbial contamination.
- Guidelines from the Personal Care Products Council (PCPC): This organization represents the U.S. cosmetics industry, and its guidelines include recommendations on controlling water activity to ensure the microbiological safety of products.
Although there is no explicit regulatory requirement for the use of water activity analyzers, their use is strongly recommended and supported by major standards and guidelines to ensure the microbiological safety of cosmetic products. Integrating the aWLife instrument by Steroglass srl into the quality control process can help comply with these standards and ensure product safety and quality by facilitating the identification of products at risk of microbial contamination. By incorporating advanced analytical techniques such as this, cosmetic manufacturers can improve their quality control processes, ensuring compliance with regulatory standards and protecting consumer health.