Purpose: This study evaluated the ability of three sanitizers in inactivating fecal coliforms in cell cultures and on coupons made from blueberry contact surface materials.
Methods: Five bi-strain mixtures of fecal coliforms (105 CFU/ml) were exposed to 5 ppm active chlorine dioxide (ClO2), 200 ppm quaternary ammonium (QAC) or 3 ppm ozonated water (OW) for 1 minute. In a separate study, 100 µl of each cell suspension was inoculated on coupons (2×5 cm2) made of high-density polyethylene, stainless steel, rubber, polyvinyl chloride, polypropylene and polyurethane. The surfaces were air dried for 4 h at 10°C before being treated with aforementioned sanitizers. Surviving cells in both assays were enumerated on LB and MAC.
Results: In the cell culture assays, ClO2, caused an average of 3.01 log reduction whereas QAC and OW both resulted in a 4.97 log reduction on MAC. On LB, a 2.77, 5.15 and 5.12 log reduction was obtained by treatment with ClO2, QAC and OW, respectively. On average, only 0.64, 1.51 and 1.38 log reductions were observed on LB when the contact surfaces were treated with ClO2, QAC or OW. On MAC, treatment with ClO2, QAC and OW caused 1.13, 2.04 and 1.94 log reductions. Overall, no significant difference was observed in the performance of QAC and OW. However, their efficacies were significantly higher than the efficacy of ClO2. Polypropylene and polyvinylchloride had the highest, whereas high-density polyethylene had the lowest bacterial counts after sanitation.
Significance: QAC and OW are more effective than ClO2 for fecal coliform inactivation. The type of bacterial contact surface had a significant influence on the efficacy of sanitizers. Dried bacterial cells on their contact surface are much more difficult to inactivate than those in liquid cultures.