PRESERVATIVE EFFICACY TESTING 7 self-sterilization of 10 6 CFU/ml is 24 hours. Considering the daily use of cosmetics, this specification may be appropriate. The self-sterilization periods obtained through D- values were confirmed by the experimental data, as they allow us to foresee if the preservative system is able to meet the requirements of the official methods by calcu- lating the rate of reduction after 7, 14, 21, and 28 days of the test. CONCLUSION In spite of the critics of the linear regression method, the method proved to be useful in the selection of an ideal preservative system for the evaluated product. However, before defining a system, one may want to consider confirming suitability using an official method. Thus, it is possible to conclude that among all the tested systems, the one used in formula 9 achieved the best results. REFERENCES (1) British Pharmacopoeia (Her Majesty's Stationary Office, London, 1998). (2) "Microbiological Tests, Antimicrobial Preservatives--Effectiveness," in United States Pharmacopeia XXIV (USP Convention, Rockford, MD, 2000). (3) "General Texts, Efficacy of Antimicrobial Preservation," in European Pharmacopeia, Third Edition (Coun- cil of Europe, Strasbourg, 1997). (4) "A Guideline for the Determination of Adequacy of Preservation of Cosmetics and Toiletry Formu- lations, in CTFA Technical Guidelines, C. N. McEwen and A. S. Curry, Eds. (Cosmetic, Toiletry and Fragrance Assn., Washington, D.C., 1993). (5) D. S. Orth, Linear regression method for rapid determination of cosmetic preservative efficacy, J. Soc. Cosmet. Chem., 30, 321-332 (1979). (6) D. S. Orth, Establishing cosmetic preservative efficacy by use of D-value, J. Soc. Cosmet. Chem., 31, 165-172 (1980). (7) D. S. Orth and L. R. Brueggen, Preservative efficacy testing of cosmetic products--Rechallenge test- ing and reliability of the linear regression method, Cosmet. Toiletr., 97, 61-65 (1982). (8) D.S. Orth, C.M. Lutes, S. R. Milsrein, and J.J. Allinger, Determination of shampoo preservative stability and apparent activation energies by the linear regression method of preservative efficacy testing,d. Soc. Cosmet. Chem., 38, 307-319 (1987). (9) D. S. Orth, Standardizing preservative efficacy test data, Cosmet. Toiletr., 106, 45-51 (1991). (10) D. S. Orth, R. F. Barlow, and L. A. Gregory, The required D-value--Evaluating product preservation in relation to packing and consumer use/abuse, Cosmet. Toiletr., 107, 39•43 (1992). (11) D. K. Brannan, Cosmetic preservation,J. Soc. Cosmet. Chem., 46, 199-220 (1995). (12) S. V. W. Sutton, R.J. Franco, M. F. Mowrey-McKee, S.C. Busschaert, J. Hamberger, and D. W. Proud, The D-value determinations are an inappropriate measure of disinfecting activity of common contact lens disinfecting solutions, Appl. Environ. Microbial., 57, 2021-2026 (1991). (13) G. E. Borovian, Pseudomonas cepacia: Growth in and adaptability to increased preservative concentra- tions, J. Soc. Cosmet. Chem., 34, 197-203 (1983). (14) J. Close and P. A Nielsen, Resistance of a strain of Pseudomonas cepacia to esters of p-hydroxy-benzoic acid, Appl. Environ. Microbiol., 31,718-722 (1976).

j. Cosmet. Sci., 54, 9-20 (January/February 2003) Skin hydration effects, film formation time, and physicochemical properties of a moisture mask containing Monostroma nitidium water-soluble mucilage RONG HUEI CHEN and WEEI YUU CHEN, Department of Food Science, National Taiwan Ocean University, Taiwan. Accepted for publication May 3, 2002. Synopsis The objectives of the study were to explore the effects of using the water-soluble mucilage of Monostroma nitidium to replace the humectant and half of the thickening agent on the rheological properties, color, storage stability, water-holding capacity, and film formation time of moisture masks thus prepared. Results showed that moisture masks containing water-soluble mucilage were pseudoplaxtic fluids. The apparent viscosity of these moisture masks decreased with increasing shear rate but increased with increasing con- centration of the aqueous extracts used. The water-holding capacity of moisture masks containing 1% aqueous extracts and 1% hydroxyethyl cellulose (HEC) were similar to those containing 2% HEC and 5% 1-3 butadiene (humectant) but better than those containing 2% methyl cellulose (MC) and 5% humectant. The film formation time of moisture masks containing different concentrations of aqueous extracts decreased with increasing concentration of the aqueous extract used. The storage stability of a moisture mask con- taining 1% aqueous extract and 1% HEC was similar to that containing 2% HEC and 5% humectant and better than those containing 2% MC and 5% humectant. The safety test resulted in no erythema based on the Draize score test. The pH was between 7.1 and 7.5 for all moisture masks studied. INTRODUCTION Monostroma nitidium, a green laver, is readily obtainable because it is cultured as a food in Japan (1,2). Maeshige (3) reported that low-molecular carbohydrate fractions in Monostroma nitidium were analyzed as fructose, glucose, and sucrose. Lii (4) reported that storage polysaccharide in green alga were or-l,4 and or-l,6 linkage polyglucoses. The major component sugars were rhamnose, glucose, xylose, and galactose. It is necessary for skin to maintain a certain level of moisture for normal functioning and vitality. When skin moisture content decreases to a certain level, the skin loses its normal softness and pliability and becomes haMened and embrittled. The major factor affecting skin moisture content is a natural moisturizing factor (NMF) existing in the stratum corneum. Besides, on the surface of the skin, water, water-soluble compounds, and lipids form a protecting film that assists the stratum corneum in minimizing the evaporation of water and alleviating intrinsic and extrinsic detrimental factors such as age, body temperature, humidity, and seasonal changes (5). Of the two types of humec-