Sensory analysis of cosmetic powders: personal care ingredients and emulsions.

OBJECTIVE: The powders are ingredients increasingly used in the formulation of cosmetic products for the sensory qualities they give. The objective of this study was the development of a lexicon and a referential for sensory characterization of these pure raw materials as well as formulations which contain them. METHODS: Eleven expert panellists from Ecole de biologie industrielle de Cergy (France) developed a lexicon and a referential based on 12 powders of different chemical natures. The selected attributes were then used for performing a quantitative descriptive profile of two powders and an emulsion containing or not one of these two powders. RESULTS: A lexicon has been established through a consensus approach of the panel. It contains seven attributes that allow the evaluation of the powders in four phases: the appearance, the pickup, the application and the after-feel. This lexicon contains definitions and assessment protocols and provides references products. The quantitative descriptive profile of two powders of the same chemical nature, but different in physical quality showed significant differences in sensory level between products. These same attributes used to evaluate an emulsion containing the powder or not allowed to prove the contribution of these raw materials on the sensory specificities of the emulsion. CONCLUSION: The lexicon developed in this study can be used for assessment of other powders but also to define the quantities necessary to put in the formulation to meet the sensory characteristics of these raw materials powder.

Recent developments in the sensorial assessment of cosmetic products: a review.

Cosmetic development is not exclusively guided by notions of rational effectiveness but also by notions of sensoriality. Thus, the sensorial properties of a cosmetic product are studied using internationally recognized discriminating or descriptive methods. Descriptive sensory profiling is an essential tool in this process as it allows an experienced panel to assess the qualitative and quantitative characteristics of a product. The results obtained with this method enable to get a more accurate image of the product. However, given the new demands of the industrial world and the new innovation paths (shorter development times, complex products or willingness to include the consumers in the process) a need to access new methods has arisen. These 'alternative' methods that offer product positioning, ratings and attribute citation frequency, can be implemented with either a panel of experts or with consumers. The flash profile, the pivot® profile or the check all that apply (CATA) are just a few of the methods that the cosmetic professionals have started to test. This article reviews the methods used in the sensory assessment of cosmetic products. The analysis carried out shows that the complementarity application of sensory assessment is essential in the upstream innovation phase of a product.

Predictive microbiology for cosmetics based on physicals, chemicals and concentration parameters.

OBJECTIVE: Challenge test (CT) is essential to assure the efficiency of the preservative system in products. A previous study realized by our staff in 2012, carried out to evaluate the influence of three parameters (ethanol, pH and water) on the microbiological cosmetics products conservation. Following this work, a correlation between aw (based on the glycerine concentration) and the selected parameter has been demonstrated. In the present study, smaller limits of ethanol, pH and glycerine were applied to determinate CT necessity. METHODS: Sixteen stables O/W cosmetics creams with different concentration of ethanol (1-19%), glycerine (3-16%) and different pH (6-11) were formulated. To evaluate the efficiency of the different formulations, CTs were performed according to the International Standard ISO 11930:2012. To determine the influence of the parameters, a D-optimal plan generated by Design Expert(®) was applied. Design of Experiments software offers to plan, estimate and control the statistics and models for factorial and no-factorial designs. RESULTS: Challenge tests results show that 10 formula passed criteria A, two passed criteria B and four are not conform. Mostly, an ethanol concentration higher than 16% exempts products of CT. It has been shown that an ethanol concentration between 10.5% and 16%, and an glycerine concentration >10%; or if the ethanol concentration is between 5% and 10.5%, glycerine is >6% and pH is ≥10, the CT is not required. Ethanol has a significant impact on conservation and especially when it is correlated with glycerine and pH. Finally, a glycerine concentration higher than 16% exempts products of CT. CONCLUSION: Following the analysis of the different concentration, a correlation between glycerine and ethanol that directly influence microbiological protection of cosmetics products has been established. Indeed, by controlling ethanol, pH and glycerine, many products may be exempted from the CT.

Determination of the influence of factors (ethanol, pH and a(w) ) on the preservation of cosmetics using experimental design.

OBJECTIVE: Ethanol, pH and water activity are three well-known parameters that can influence the preservation of cosmetic products. With the new constraints regarding the antimicrobial effectiveness and the restrictive use of preservatives, a D-optimal design was set up to evaluate the influence of these three parameters on the microbiological conservation. METHODS: To monitor the effectiveness of the different combination of these set parameters, a challenge test in compliance with the International standard ISO 11930: 2012 was implemented. The formulations established in our study could support wide variations of ethanol concentration, pH values and glycerin concentration without noticeable effects on the stability of the products. RESULTS: In the conditions of the study, determining the value of a single parameter, with the tested concentration, could not guarantee microbiological conservation. However, a high concentration of ethanol associated with an extreme pH could inhibit bacteria growth from the first day (D0). Besides, it appears that despite an aw above 0.6 (even 0.8) and without any preservatives incorporated in formulas, it was possible to guarantee the microbiological stability of the cosmetic product when maintaining the right combination of the selected parameters. CONCLUSION: Following the analysis of the different values obtained during the experimentation, there seems to be a correlation between the aw and the selected parameters aforementioned. An application of this relationship could be to define the aw of cosmetic products by using the formula, thus avoiding the evaluation of this parameter with a measuring device.

Optimization of preservatives in a topical formulation using experimental design.

Optimizing the preservative regime for a preparation requires the antimicrobial effectiveness of several preservative combinations to be determined. In this study, three preservatives were tested: benzoic acid, sorbic acid and benzylic alcohol. Their preservative effects were evaluated using the antimicrobial preservative efficacy test (challenge-test) of the European Pharmacopeia (EP). A D-optimal mixture design was used to provide a maximum of information from a limited number of experiments. The results of this study were analysed with the help of the Design Expert software and enabled us to formulate emulsions satisfying both requirements A and B of the EP.