Assessment and Mitigation of Bacterial and Fungal Contamination in Refrigerator Waterlines

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.