A comparison of saturated steam and superheated steam for inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes biofilms on polyvinyl chloride and stainless steel

This study was performed to compare the effectiveness of saturated steam (SS) and superheated steam (SHS) in the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes biofilms on polyvinyl chloride (PVC) and stainless steel. Biofilms were formed on PVC and stainless steel coupons by using a mixture of three strains each of three foodborne pathogens at 25 degrees C. After biofilm development, PVC and stainless steel coupons were treated with SS at 100 degrees C and SHS at 125,150, 175, and 200 degrees C for 5,10, 20, and 30 s on both sides. The viable cell numbers of biofilms were significantly (p < 0.05) reduced as SHS temperature and exposure time increased. For all biofilm cells, SHS treatment resulted in an additional log reduction compared to SS treatments. After exposure to 200 degrees C steam for 30 s or 10 s on PVC or stainless steel, respectively, the numbers of biofilm cells were reduced to below the detection limit (1.48 log). This study demonstrated that SHS treatment effectively reduced populations of biofilm cells and reduced disinfection time compared to SS treatments and further evaluated its potential as an excellent intervention for controlling microbial biofilms and enhancing safety in the food processing industry. (C) 2013 Elsevier Ltd. All rights reserved.