title: Effect of frequency and waveform on inactivation of Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in salsa by ohmic heating.
abstract: The effect of frequency of alternating current during ohmic heating on electrode corrosion, heating rate, inactivation of food-borne pathogens, and quality of salsa was investigated. The impact of waveform on heating rate was also investigated. Salsa was treated with various frequencies (60 Hz to 20 kHz) and waveforms (sine, square, and sawtooth) at a constant electric field strength of 12.5 V/cm. Electrode corrosion did not occur when the frequency exceeded 1 kHz. The heating rate of the sample was dependent on frequency up to 500 Hz, but there was no significant difference (P > 0.05) in the heating rate when the frequency was increased above 1 kHz. The electrical conductivity of the sample increased with a rise in the frequency. At a frequency of 60 Hz, the square wave produced a lower heating rate than that of sine and sawtooth waves. The heating rate between waveforms was not significantly (P > 0.05) different when the frequency was >500 Hz. As the frequency increased, the treatment time required to reduce Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium to below the detection limit (1 log CFU/g) decreased without affecting product quality. These results suggest that ohmic heating can be effectively used to pasteurize salsa and that the effect of inactivation is dependent on frequency and electrical conductivity rather than waveform.
authors.affiliation: Department of Food and Animal Biotechnology and Department of Agricultural Biotechnology, Center for Agricultural Biomaterials, and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, South Korea.
authors.forename: Su-Yeon
authors.initials: SY
authors.lastname: Lee
authors.forename: Sangryeol
authors.initials: S
authors.lastname: Ryu
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kang
mesh_terms: D004203:Disinfection / Q000379:methods*; D019453:Escherichia coli O157 / Q000502:physiology / Q000528:radiation effects*; D005516:Food Microbiology; D006361:Heating / Q000379:methods*; D050296:Microbial Viability / Q000528:radiation effects*; D008872:Microwaves; D012486:Salmonella typhimurium / Q000502:physiology / Q000528:radiation effects*