Inactivation of Enterobacter Aerogenes in a Pipeline System Using Plasma Activated Water

The objective of this study was to develop a cleaning-in-place (CIP) methodology using plasma activated water (PAW) and compare its effectiveness with chlorine wash. A bench-top CIP pipeline system (6.35 mm inner dia.) consisting of vinyl tubing, tees, and elbows was put together. Tryptic Soy Broth (TSB) solution (~9 log CFU/ml) containing E. aerogenes was circulated through the system to allow the inner surface of the system to be inoculated with bacteria. After 24 h of circulation, 500 ml PAW or chlorine (100 ppm) or water (as control) was used to detach and/or inactivate the E. aerogenes attached on the inner surface the system. In Case 1 the average flow velocity of PAW was 0.11m/s and the washing time was 15 min. The system was then disassembled and the number bacteria adhering to the inner surface of various components were enumerated. Washing the pipeline system using distilled water only reduced the number of E. aerogenes adhering to surface by 0.65, 1.0, and 1.3 log cfu/cm² on the tees, elbows, and tubing, respectively. However, washing the system using PAW reduced the number of E. aerogenes on tees, elbows, and tubing by 3.0, 3.2, and 3.8 log cfu/cm², respectively. The inactivation achieved using PAW was similar to using 100 ppm chlorine, which reduced the number of E. aerogenes on tees, elbows, and tubing by 2.8, 2.9, and 2.7 log cfu/cm². Washing at average flow velocity of 0.22 m/s for 15 min decreased the contamination further by 0.9 log cfu/cm² at all locations more compared to lower average washing flow velocity of 0.11 m/s. The results show that PAW can be a potential alternative to conventional sanitizers and a good cleaning agent for CIP applications in food industry.