100 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) G. M. Golden, D. B. Guzek, A. H. Kennedy, J. E. McKie, and R. O. Potts, Stratum corneum lipid phase transitions and water barrier properties, Biochemistry, 26, 2382-2388 (1987). M. J. Janiak, D. M. Small, and G. G. Shipley, Temperature and compositional dependence of the structure of hydrated dimyristoyl lecithin, J. Biol. Chem., 254(13), 6068-6078 (1979). S. E. Friberg, L. B. Goldsmith, D. W. Osborne, and R. Brown, The penetration of 2-(alkoyloxy) 1- [alkoyloxy)methyl]-ethyl-7-(4-heptyl-5, 6)-dicarboxy-2-cyclohexene-l-yl) heptanoate into human stratum corneum, J. Soc. Cosmet. Chem, 39, 283-290 (1988). D. W. Osborne, The skin softening properties of maleated soybean oil, Cosmet. Toiletr., 103, 57-70 (1988). M.D. Batt and E. Fairhurst, Hydration of the stratum corneum, Int. J. Cosmet. Sci., 8, 253-264 (1986). D. L. Bissett and J. F. McBride, Skin conditioning with glycerol,J. Soc. Cosmet. Chem. 35, 345-350 (1984). M.D. Batt, W. B. Davis, E. Fairhurst, W. A. Gerrard, and B. D. Ridge, Changes in the physical properties of the stratum corneum following treatment with glycerol, J. Soc. Cosmet. Chem., 39, 367-381 (1988). M. A. Lampe, M. L. Williams, and P.M. Elias, Human epidermal lipids: Characterization and modulations during differentiation, J. Lipid Res,, 24, 131-140 (1983). G. Imokawa and M. Hattori, A possible function of structural lipids in the water-holding properties of the stratum corneum, J. Invest. Dermatol., 84(4), 282-284 (1985). G. Imokawa, H. Kuno, and M. Kawai, Stratum corneum lipids serve as a bound-water modulator, Jo Invest. Dermatol., 96(6), 845-851 (1991). G. Imokawa, S. Akasaki, A. Kawamata, S. Yano, and N. Takaishi, Water-retaining function in the stratum corneum and its recovery properties by synthetic pseudoceramides, J. Soc. Cosmet. Chem., 49, 273-285 (1989).

j. Soc. Cosmet. Chem., 44, 101-107 (March/April 1993) Relationship between sensory and instrumental evaluations of mouth odor HOLLANDRA P. NILES and ABDUL GAFFAR, Colgate-Palmolive Technical Center, 909 River Road, Piscataway, NJ 00854. Received March 20, 1992. Presented in part at the annual session of the AADR, Washington, D.C., March 1986. Synopsis Two methods are currently available to assess mouth odor: subjective evaluation (sensory rating) and gas chromatographic (GC) analysis of the volatile sulfur compounds (VSC), hydrogen sulfide, methyl ruercap- tan, and dimethyl sulfide in mouth air. The purpose of this study was to examine the correlation between these two methods in a human clinical study. Twenty adults participated in the study. The morning mouth odor of each subject was assessed by two expert sensory evaluators on a scale of 0 to 8 (showing increasing odor intensity). Following sensory evaluations, mouth air samples from each subject were then obtained and analyzed by GC for VSC. The study was divided into three phases, viz., a control, a test, and a recovery phase. Each phase lasted for three days, and two readings on the second and third day of each phase were obtained by both methods. During the test phase, the subjects brushed their teeth twice a day with a standard fluoride-containing dentifrice, and morning mouth odor determinations were conducted as de- scribed above. During the control and recovery phase, the subjects practiced oral hygiene ad libitum. Correlation coefficients (r) between sensory ratings and GC readings (VSC--ng/ml) of mouth air were 0.22, 0.77, and 0.78 during the control, the test, and the recovery periods, respectively. The latter two were significant at p = 0.01. The ratios of the GC reading to the sensory rating were consistent over the range of values obtained an average factor of 3.2 would predict the corresponding GC reading for a given sensory rating in this study. For example, VSC by GC of 25.8 ng/ml of mouth odor provided a sensory rating of 8 (strong odor). This indicates that the objective evaluation of mouth odor by GC does correlate with a subjective sensory rating of mouth odor. The GC method therefore provides us with useful instrumental measurements (ng/ml) that can be translated into a consumer-perceivable odor intensity. INTRODUCTION It has been previously shown that the volatile sulfur compounds (VSC) such as H2S, CH3SH, and (CH3)2S are responsible for local mouth odor in healthy individuals (1). These VSC components arise from the putrefaction of salivary proteins and amino acids by gram-negative oral microorganisms (2) and can be detected in direct mouth air by a gas chromatographic method or by a sensory method (3). Since the sensory method is subjective, it is highly desirable to develop an objective instrumental method to assess offensive local mouth odor. lol