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An Aspergillus mold was isolated that had contaminated an unpreserved semisoft baked cookie with visible mycelial growth. Due to the xerophilic nature of the contaminating mold, the Aspergillus isolate went undetected using conventional plating media and incubation times. Spread plating onto rose bengal osmophilic potato dextrose (rose-osmo) agar, a reduced water activity (aw) medium, was used for isolation and enumeration of the isolate from contaminated cookies and in microbiological assessments of the production facility. Rose-osmo plates were sealed in plastic and incubated at 25°C for up to 6 weeks to allow the isolate to sporulate. The minimum aw that permitted growth was determined by inoculating both MY70GF agar plates and production cookies with fresh spores of the Aspergillus isolate. Inoculated samples were incubated for up to 6 weeks in humidity chambers adjusted to various moisture levels. The minimum aw required for growth of the Aspergillus isolate was found to be between 0.60 and 0.65 on MY70GF agar and approximately 0.65 on the cookie. To evaluate the potential delayed growth of the isolate on reformulated cookies of a lowered aw, long-term growth studies were conducted on cookies adjusted to various aw levels and monitored for up to 280 days. In these studies, the minimum aw test range found to support visible mycelial growth of the Aspergillus isolate was 0.67. Microbiological assessment of the production facility identified potential sources of xerophilic molds and the Aspergillus isolate (teleomorph Eurotium chevalieri) and identified the manner in which the cookies became contaminated. These methods and results proved helpful in both production and process risk assessments and in successful reformulation of the cookie at an aw low enough to prevent spoilage and provide an organoleptically acceptable product.

ABSTRACT. The objective of this paper is to describe a test method to determine a Clean Air Delivery Rate-(CADR) type measurement for an air cleaner when challenged with microbiological aerosols. The method is a modi cation of the Association of Home Appliance Manufacturers (AHAM) Standard AC-1, "Standard Method for Measuring Performance of Portable Household Electric Cord-Connected Room Air Cleaner," which determines the CADR for three different particulate matter challenges (smoke, dust, and pollen). The ability to extend the AHAM method to microbial aerosols follows the tradition of the AHAM test of using realistic particle challenges and allows a means to compare and evaluate different brands of room air cleaners regarding characteristics signi cant to product use. This is a useful approach for evaluating a wide range of air cleaning devices.The test procedure requires both a natural decay measurement and a particulate decay measurement. The particulate decay measurement is de ned as the decay while the air cleaner is operating. The aerosol generation and collection optimized the ability of three very different organisms to survive and remain culturable. The results showed that the AHAM test method was successfully adapted to allow testing with actual organisms.