SENSORY CHARACTERIZATION OF COSMETIC EMULSIONS 85 (remove/add) the oily components (i.e., emollients) in the formula. However, signifi cant changes cannot be expected from such a modifi cation, as it has been demonstrated using trained panelists that the emulsifi er choice plays the dominant role in determining the aesthetics of a skin care emulsion (21,22). Emulsifi ers determine the skin feel during the initial phases of skin sensory evaluation, including assessment of appearance, pick-up, and rub-out. Emollients have a substantial role during the later phases (afterfeel) of skin sensory evaluation. Afterfeel parameters are a mix of effects from emulsifi er and emollient selections (22). Although consumer profi ling techniques have become more relevant, only a few stud- ies reported about the application of such techniques to cosmetic and personal care products. The aim of this work was to have consumers evaluate the sensory character- istics of six cosmetic emulsions before, during, and after application using a CATA survey. The six emulsions represented three different types of emulsions with different skin feel and esthetic attributes however, emulsions within the same group were sim- ilar. As mentioned previously, it is known from the literature (21,22) that different types of emulsions provide different skin feel, even when the same emollient is used. We set out to examine whether consumers can feel these differences and differentiate between samples based on their sensory characteristics. If consumers can differentiate between the samples based on their sensory characteristics and the differences can be clearly attributed to the formulation technology and composition of the products, it means that a carefully designed CATA survey using consumers could serve as an easy, quick, economical, and useful approach in the characterization of cosmetic emulsions during the product development phase. In addition, if our study using untrained con- sumers indicates that emulsifi ers are the primary determinants of skin feel and aesthet- ics of cosmetic emulsions, a concept that was previously proven using trained panelists, it would confi rm the validity of CATA surveys and indicate their reliability as screen- ing tools. MATERIALS AND METHODS MATERIALS Heptyl undecylenate (LexFeel® Natural Inolex, Philadelphia, PA) was used as the light emollient, whereas clear olive oil (AC Clear olive oil Active Concepts LLC., Lincolnton, NC) was used as the rich emollient. A combination of polyglyceryl-10-hexaoleate and polyglyceryl-6-polyricinoleate (Pelemol® P-1263 Phoenix Chemical, Inc., Somerville, NJ), as well as lauryl PEG-9 polydimethylsilcoxyethyl dimethicone (KF 6038 ShinEtsu Silicones, Akron, OH), polyglyceryl-10-stearate (Polyaldo® 10-1-S Lonza, South Plain- fi eld, NJ), cetyl alcohol (Making Cosmetics, Snoqualmie, WA), and a combination of sorbitan stearate and sorbityl laurate (Arlacel™ LC Croda, Edison, NJ) were used as emulsifi ers for the emulsions. Propanediol (Zemea® DuPont Tate & Lyle Bio Products Company, LLC, Loudon, TN) was used as the humectant. A mixture of propylene glycol, diazolidinyl urea, methyl paraben, and propyl paraben (Germaben™ II Ashland, Bridge- water, DE) was used as the preservative. Finally, deionized water of 18 M purity was used as the vehicle/solvent for the aqueous phase. The exact composition of the emulsions is shown in Tables I–III.

JOURNAL OF COSMETIC SCIENCE 86 METHODS Emulsions. Six cosmetic emulsions were formulated, namely, two water-in-oil (W/O) emulsions, two steric-stabilized oil-in-water (O/W) emulsions, and two liquid crystal– stabilized O/W emulsions. These three groups differed in the type and amount of emulsi- fi ers used. In each group, one emulsion contained a single emollient that is generally perceived as light in terms of skin feel, whereas the second emulsion contained a combi- nation of the light emollient and a small amount of olive oil as a second emollient, which provides a rich skin feel. Tables I–III show the composition of each emulsion. The overall emollient phase volume of the emulsions was held constant, and the emulsifi ers were used at the recommended use levels for stability. Each sample (2 g) was provided to the participants in a 3 g clear plastic jar with a white cap. Identifi cation numbers were marked on each cap as well as on the bottom of each jar. All samples were stored at ambient conditions in the testing room for at least an hour before conducting the study. CONSUMER PANEL Fifty consumers, of ages ranging between 18 and 55 years, were recruited for the study. Consumers from both genders and any ethnicity were invited to participate in the study. Table I I ngredients and Percentage of Ingredients in the Steric-stabilized O/W Emulsions Ingredient—INCI name Emulsion 1 Emulsion 2 % (w/w) % (w/w) Heptyl undecylenate 15 10 Olive oil — 5 Polyglyceryl-10-stearate 5 5 Cetyl alcohol 3 3 Water 71 71 Propanediol 5 5 Propylene glycol (and) diazolidinyl urea (and) methyl paraben (and) propyl paraben 1 1 Table II Ingredients and Percentage of Ingredients in the Liquid Crystal–Stabilized O/W Emulsions Ingredient—INCI name Emulsion 3 Emulsion 4 % (w/w) % (w/w) Heptyl undecylenate 15 10 Olive oil — 5 Water 75 75 Sorbitan stearate (and) sorbityl laurate 4 4 Propanediol 5 5 Propylene glycol (and) diazolidinyl urea (and) methyl paraben (and) propyl paraben 1 1