Assessment and Mitigation of Bacterial and Fungal Contamination in Refrigerator Waterlines

Abstract

Three experiments were conducted on the recovery of microorganisms associated with refrigerator water lines. In the first experiment, between 2 and 3 logs CFU/ml were recovered from 100 different refrigerators’ residential water and ice lines. In a second experiment, plastic tubing segments cut from commercial refrigerator waterline systems were inoculated with the bacterium Pseudomonas aeruginosa and a fungal strain of Aspergillus flavus. Either 0.02% peracetic acid (PAA) exposure for 2 min or 0.03% PAA exposure for 1 min resulted in no recoverable bacteria cells, however, 0.25% PAA contact for 2 min was needed to eliminate detection of fungal cells. The third experiment tested sanitation of a water system inoculated with a mixed culture of P. aeruginosa and A flavus with a water filter cartridge filled with 3.5% PAA. The 3.5% concentration was determined using a computer simulation for mixing during a cleaning cycle that would yield a minimum concentration of at least 0.25% throughout the water system. After loading a water filter cartridge containing 3.5% PAA, allowing water to flow into the system for 15 s, and then allowing the system to sit for 5 min, no viable P. aeruginosa or A flavus cells were recovered up to 10 days after treatment.