Robert Miller, Rose F Durham – DuPont Tate & Lyle Bio Products, US PRESERVATIVES
Bio-based propanediol boosts preservative efficacy
Zemea1 bio-derived propanediol,
manufactured by DuPont Tate & Lyle Bio Products, can be used to replace petroleum based glycols such as propylene glycol (PG), butylene glycol (BG) or glycerin in cosmetic and personal care formulations. It is currently being used as a humectant, emollient, and/or natural solvent in skin and hair care products and as a solvent for botanical extraction and dilution. It is also being used as a carrier for active ingredients, as an ingredient in natural preservative systems and for developing natural esters. Previously in this journal (September 2010) the results of various technical and consumer tests conducted to evaluate the performance of bio-derived propanediol as compared to traditional glycols and glycerin were reported. New testing recently conducted looked at the potential for bio-derived propanediol to boost the efficacy of preservatives in a personal care formulation.
Preservatives
A preservative is a natural or synthetic chemical that is added to products such as foods, cosmetics or pharmaceuticals to prevent spoilage. The primary reason preservatives are added to cosmetics and personal care formulations is to ensure the safety of these products for consumers. Microorganisms such as bacteria, yeasts and moulds are present in the air, in water and on human skin. They can cause irritation and infection when exposed to human skin and result in instability of the formulation including separation of the emulsion and bad odour. The use of preservatives in aqueous based cosmetics and personal care products prevents the growth of microorganisms.
Due to the potential health and safety risks for consumers, it is necessary for formulators to find a preservative system that will inhibit the growth of multiple microorganisms such as bacteria, yeasts and moulds. Formulation preservation is typically achieved at levels between 0.5% and 2% by weight of preservative.
Zemea
1,000,000 100,000 10,000 1000 100 10 1
Propylene glycol Butylene glycol Time (hours) Figure 6 CTFA Challenge Test: Group III Molds and Yeasts Figure 1: CTFA challenge test: Group III moulds and yeasts.
While preservative mechanisms and effectiveness may be similar, it is common for formulators to combine preservatives together in an attempt to create a synergy that can reduce the amount needed to effectively protect a product. Over the last couple of years,
consumers have been expressing concerns about the safety and use of preservatives in cosmetics and personal care products. Parabens, the most widely used preservative, have been singled out; and marketers have been touting paraben-free and/or preservative-free product claims
Table 1: Formulation used in challenge test. Ingredient
Water, deionised Zemea propanediol Xanthan gum Liponate GC Sesame oil
Lipomulse 165 Promulgen D DC 200-100
NaOH /Citric acid (20% sol) Preservative*
INCI Name Water
Propanediol Xanthan gum
Caprylic Capric Triglyceride
Sesamum Indicum (Sesame) seed oil Glyceryl Stearate
Cetearyl Alcohol and Ceteareth 20 Dimethicone
Sodium hydroxide/citric acid Preservative*
for some of their formulations. Ingredient suppliers have been developing new, natural preservative systems to meet the demand for natural product formulations and to provide alternatives to paraben- based preservatives.
The intent of this paper is to discuss the results of a recent study where the potential for boosting preservative efficacy by using bio-derived propanediol in an aqueous-based cosmetic formulation was studied using standardised microbiology guidelines, known as preservative efficacy testing or challenge tests.
Weight, % qs to 100%
0 to 6.0 0.3
10.0 5.0 2.0 1.5 1.0
qs to pH 5.0-6.0 (Table 2)
April 2012 PERSONAL CARE 85
0 24 72 336 672 6
48 166 504
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