Optimization of cosmetic preservation: water activity reduction

Area of Science:

• Cosmetic Science
• Microbiology
• Physical Chemistry

Background:

• Cosmetic preservation is crucial for industrialization, with self-preserved formulations being a key area of interest.
• Water activity is a critical parameter influencing microbial growth in cosmetic products.
• Reducing water activity is a viable strategy to enhance the preservation of cosmetics.

Purpose of the Study:

• To investigate the impact of humectants on water activity in cosmetic formulations.
• To understand how humectant concentration, chemical structure, and formulation process affect water activity.
• To evaluate the consequential effect of reduced water activity on cosmetic product preservation.

Main Methods:

• Studied water-humectant binary mixtures, varying glycol and glycerin content, glycol structure, and purity.
• Employed molecular modeling (DFT calculations) to elucidate the impact of glycol chemistry on water binding.
• Applied findings to five cosmetic formulations and conducted challenge tests against five microbial strains.

Main Results:

• Increased humectant concentration directly correlated with decreased water activity.
• Glycol chemical structure influenced water activity; propan-1,2-diol was more effective than propan-1,3-diol.
• Optimized cream formulation achieved a 6.6% reduction in water activity, leading to improved preservation.

Conclusions:

• Both fabrication process and humectant concentration significantly influence water activity.
• Glycol's hydroxyl group position and alkyl group presence impact water binding, as supported by DFT calculations.
• Reduced water activity effectively inhibited or slowed microbial growth in a cosmetic cream, enhancing its preservation.