AUTOMATED SCREENING METHOD FOR DETERMINING OPTIMUM PRESERVATIVE SYSTEMS FOR PERSONAL AND HOME CARE PRODUCTS

A procedure was designed to determine the minimum preservative level ( MPL) for personal and home care products. A highly preserved sample an d an unpreserved sample were combined at different concentrations with in a 96-well microtiter plate by using an autodilutor. A unique tip de sign made it possible to accurately deliver viscous test materials tha t cannot be dispensed using vacuum- or fluid-filled systems. After ino culation, the sample was evaluated at a specified time interval for th e presence of surviving bacteria, yeast, and mold. The lowest concentr ation of preservative with no microbial growth is the recommended leve l of preservative for the product. Because sample turbidity may interf ere with determination of the endpoint, a colorimetric endpoint was us ed to indicate growth of microorganisms and to differentiate product f rom growth. The predicted levels were tested with a modified Cosmetic, Toiletry, and Fragrance Association method. The method successfully p redicted effective preservative levels in many personal and home care products with a broad range of viscosities.