title: A new alternative to cosmetics preservation and the effect of the particle size of the emulsion droplets on preservation efficacy.
abstract: OBJECTIVE
  This study describes a new alternative combination preservative containing caprylyl glycol, phenethyl alcohol and glyceryl caprylate and investigates the effects of the particle size of the emulsion droplet on the anti-microbial activity of the said blend in the formulation.
  
  
  METHODS
  The anti-microbial activity of the ingredients and the blend were determined via MIC, MBC, MFC and fractional inhibitory concentration (FIC) determination using the broth microdilution method. The blend inhibited the micro-organism contamination of the oil-in-water emulsion, and its performance was affected by the particle size of the emulsion droplet, as shown by the in vitro microbial challenge test.
  
  
  RESULTS
  Results show that the MIC/MBC/MFC values of the blend were lower than those of any of the ingredients used alone. Any two of the ingredients presented no antagonistic activities against all the tested micro-organisms, and synergism or additive effects were also observed. The challenge test also showed that the action of the blend against bacteria and yeast was only 0.3% and 0.2%, respectively, and mould was completely inhibited at 1.4%, meeting the requirements of the PCPC and European Pharmacopoeia. The results showed that anti-microbial activity was gradually enhanced when the particle size of the emulsion droplets increased significantly in the range of 100-900 nm. A positive correlation was found between anti-microbial activity and particle size.
  
  
  CONCLUSIONS
  The synergistic performance of caprylyl glycol, phenethyl alcohol and glyceryl caprylate and the anti-microbial activity of their blend suggest that their combination is effective and exhibits broad-spectrum anti-microbial activity. Furthermore, the results show a positive correlation between the anti-microbial activity of the preservative and the particle size of the emulsion droplets in the range of 100-900 nm, when the same concentration of the blend is used in the same formulation. The particle size of the emulsion droplets is demonstrated to be a newly discovered factor that influences the preservation of cosmetic products.
authors.affiliation: School of Perfume and Aroma Technology, Shanghai Institute of Technology, No.100, Haiquan Road, Fengxian district, Shanghai, 201418, China.
authors.forename: B
authors.initials: B
authors.lastname: Fang
authors.affiliation: Shanghai Syntec Additive Limited, No.168, Jixin Road, Minhang district, Shanghai, 201104, China.
authors.forename: M
authors.initials: M
authors.lastname: Yu
authors.affiliation: School of Perfume and Aroma Technology, Shanghai Institute of Technology, No.100, Haiquan Road, Fengxian district, Shanghai, 201418, China. zhwanp@126.com.
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Shanghai Syntec Additive Limited, No.168, Jixin Road, Minhang district, Shanghai, 201104, China.
authors.forename: F
authors.initials: F
authors.lastname: Wang
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003358:Cosmetics; D004655:Emulsions; D008826:Microbial Sensitivity Tests; D010316:Particle Size; D011310:Preservatives, Pharmaceutical
chemical_list: D000900:Anti-Bacterial Agents; D003358:Cosmetics; D004655:Emulsions; D011310:Preservatives, Pharmaceutical
keywords: caprylyl glycol; glyceryl caprylate; particle size; phenethyl alcohol; preservative