Title: Radio Frequency Electric Fields Inactivation of Lactobacillus plantarum in Apple Cider Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 13, 2007
Publication Date: August 1, 2007
Citation: Geveke, D.J. 2007. Radio Frequency Electric Fields Inactivation of Lactobacillus plantarum in Apple Cider. [abstract]. International Food Technologists Annual Meeting. Paper No. 189-44. Technical Abstract: Radio frequency electric fields (RFEF) nonthermal processing has recently been shown to be effective at reducing Escherichia coli in fruit juices. While considerable effort and progress have been made in studying the effect of RFEF processing on this gram negative bacteria, there is a total lack of research on the effect of RFEF processing on gram positive bacteria. The objective of this study was to determine the effect of RFEF nonthermal processing on Lactobacillus plantarum, a gram positive bacteria. L. plantarum ATCC 49445 was inoculated into apple cider. The inoculated cider was stored at refrigerated temperature for 2 h. The cider was RFEF processed at the following conditions: electric field strength - 0, 5, 10, and 15 kV/cm; outlet temperature - 45, 50 and 55 C, treatment time - 170 microseconds, and frequency - 5, 20, 35, 50, and 65 kHz. L. plantarum in cider processed at 55 C and 20 kHz was reduced by 0.1 log at 0 kV/cm and 3.6 log at 15 kV/cm. There was a synergistic effect of field strength and temperature; at 60 C the reduction was 0.4 log at 0 kV/cm and 4.7 log at 15 kV/cm. Inactivation decreased with increasing frequency; L. plantarum processed at 55 C and 15 kV/cm was reduced by 4.5 log at 5 kHz and 3.0 log at 65 kHz. The RFEF process was capable of inactivating L. plantarum in apple cider at nonthermal conditions. This is the first evidence that the RFEF nonthermal process is capable of inactivating gram positive bacteria.