PRESERVATIVES
Dr Alexander Thiemann, Dr Wilfried Petersen – Dr Straetmans, Germany
Emulsifier system influences O/W emulsion preservation
According to the current Cosmetic Regulation EC 1223/2009 a cosmetic product made available on the market should be safe for human health when used under normal or reasonably foreseeable conditions of use. This includes the necessity for an adequate preservation system in the cosmetic product to prevent microorganisms potentially endangering the consumer’s health from growing. The preservation of personal care products is achieved by the addition of antimicrobial ingredients. Their properties however bear the potential for undesired effects on the skin. In 1982 a positive list of approved preservatives was adopted as Annex VI to council directive 76/768/EEC,1
which later
turned into Annex V of regulation EC 1223/2009.
In addition to the approved preservatives listed on Annex V, a large number of other personal care ingredients exhibit inherent antimicrobial activity, which may be exploited to complement the overall preservation of a cosmetic product as a secondary function of the ingredients, such as chelators, wetting agents, fragrance ingredients, moisturisers, solvents, antioxidants and others.2
In fact, most
personal care ingredients either have a positive or negative effect on the overall antimicrobial effect of a formulation. Only a few ingredients are inert in the sense that they have absolutely no influence on the preservation of a product. The nature of the influence of the ingredients on the antimicrobial performance can be manifold. Some ingredients have a negative effect on microorganisms by affecting the cell membrane or the cell metabolism after penetration into the cell, while others stimulate microbiological growth by the ability of the microorganisms to metabolise the ingredient. In addition, interaction between the ingredients may lead to inactivation of antimicrobial active components. Antimicrobial components with surface activity can be attracted by detergent micelle structures in rinse-off formulations or by emulsifiers in the interphase of emulsion systems. A variation
60 PERSONAL CARE February 2016 C
Table 1: General composition of the O/W emulsions. Phase Ingredient A
Deionised water dermofeel PA-31 Glycerin (99.5%)2 dermosoft GMCY1 dermosoft 700B1 dermosoft 688 eco1 Keltrol CG-RD3
B
Emulsifier system Lanette O4 Tegin M5
Sunflower Oil6 dermofeel MCT1
dermofeel Toco 701
Sodium Hydroxide (10%)7 Citric Acid7
Suppliers 1 Dr. Straetmans
INCI (EU) Aqua
Sodium Phytate; Aqua; Alcohol Glycerin
Glyceryl Caprylate
Levulinic Acid; Sodium Levulinate; Glycerin; Aqua p-Anisic Acid Xanthan Gum (see Table 2) Cetearyl Alcohol Glyceryl Stearate
Helianthus Anuus Seed Oil Tricaprylin Tocopherol
Sodium Hydroxide Citric Acid
2 Cremer Oleo 3 CP Kelco
of the polarity of the oil-phase has an influence on the partition of antimicrobial ingredients between the water-phase and the oil-phase.
The aim of the investigation reported in this article was to identify and quantify the influence of the emulsifier system on the
Table 2: Emulsifier dosage. Emulsifier INCI 1
2 3 4 5 6
7 8
9
10 11 12
4 BASF 5 Evonik 6 Gustav Hees %
ad 100 0.2 4.0 0.5 0.3 0.2 0.2
1.5-4.0 2.0 4.0 6.0
0.15 q.s. q.s
7 Merck
preservation of the emulsion by microbiological challenge tests. Ideally it will be possible to identify specific structural features or components in the emulsifier composition that show a positive or negative interaction with the preservation performance.
%
Sodium Cetearyl Sulfate Potassium Cetyl Phosphate Glyceryl Stearate Citrate
Polyglyceryl-3 Stearate, Sodium Stearoyl Lactylate
Tetragonoloba (Guar) Gum, Magnesium Stearate Hydrogenated Lecithin, C12-16 Alcohols, Palmitic Acid
Cetearyl Alcohol, Glyceryl Stearate, Potassium Palmitoyl Hydrolyzed Wheat Protein
Polyglyceryl-3 Methylglucose Distearate Sorbitan Stearate, Sorbityl Laurate Cetearyl Alcohol, Cetearyl Glucoside Cetearyl Glucoside, Cetearyl Alcohol
2.00 3.00 5.00 3.00
Cetearyl Alcohol, Glyceryl Stearate, Stearic Acid, Sodium Lauroyl Glutamate 6.00 Sodium Citrate, Hydrolyzed Milk Protein, Xanthan Gum, Cyamopsis
2.50
4.00 5.00
4.00 0.50 2.00 5.00
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