M. Lenczewski et Ll. Kananen, AUTOMATED SCREENING METHOD FOR DETERMINING OPTIMUM PRESERVATIVE SYSTEMS FOR PERSONAL AND HOME CARE PRODUCTS, Journal of AOAC International, 81(3), 1998, pp. 534-539
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.