Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 22, 2006
Publication Date: June 25, 2006
Citation: Geveke, D.J., Zhang, H.Q. 2006. Kinetics of radio frequency electric fields inactivation of escherichia coli in apple cider [abstract]. International Food Technologists. Paper No. 017-10. Technical Abstract: Nonthermal radio frequency electric fields (RFEF) have recently been shown to be effective at reducing E. coli in fruit juices using pilot scale equipment. While considerable effort and progress have been made in scaling up the process and in achieving 5 log reductions, there is a lack of research focused on inactivation kinetics that addresses the needs set forth in the FDA’s report titled, “Kinetics of Microbial Inactivation for Alternative Food Processing Technologies.” The objectives of this study were to determine the variables that effect inactivation and establish an experimental protocol for obtaining statistically reliable kinetic parameters to describe survivor curves. These will form the basis for developing and evaluating a kinetic model. E. coli ATCC 23716 was inoculated into apple cider. The inoculated cider was stored at refrigerated temperature for 0, 2, 4, and 6 h. The cider was RFEF processed at the following conditions: frequency - 20, 30 and 40 kHz; temperature - 50, 55 and 60 C; and field strength - 0, 15, 20, 25, and 30 kV/cm. E. coli in cider at 60 C was reduced by 0.3 log at 0 kV/cm and 5.5 log at 25 kV/cm. Sensitivity to RFEF increased with storage time. This is the opposite effect observed with thermal processing and signifies a different mechanism of inactivation. Frequency had no effect on inactivation. Temperature had a much greater effect on inactivation than did field strength over the range of 15 to25 kV/cm. This indicates that the most important process validation parameter is temperature. The variables that effect RFEF inactivation have been determined and reliable parameters have been obtained to describe survivor curves. This is the first kinetics model developed for RFEF processing.