Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/14/2003
Publication Date: 9/30/2003
Citation: GEVEKE, D.J., BRUNKHORST, C. INACTIVATION OF SACCHAROMYCES CEREVISIAE USING RADIO FREQUENCY ELECTRIC FIELDS. JOURNAL OF FOOD PROTECTION. 2003. V. 66(9). P. 1712-1715. Interpretive Summary: Conventional heat pasteurization can affect the quality of fruit and vegetable juices. Nonthermal pasteurization methods are being developed, but have not been commercialized to a large extent. Radio frequency electric fields processing at low to moderate temperatures was studied. A unique radio frequency experimental system was designed, purchased, and built. A high electric field, 30 kV/cm, at a frequency of 20 kHz was applied to a suspension of Saccharomyces cerevisiae at 35 C. Its population was reduced by over 3 log (>99.9%). This demonstrated for the first time that inactivation is achievable at low temperatures using high electric fields. The process is enhanced at higher fields and higher temperatures. These preliminary results are encouraging and will be employed to extend the radio frequency electric fields process to fruit and vegetable juices. This will benefit industry and the public by providing superior quality liquid foods.
Technical Abstract: The application of radio frequency (RF) electric fields was investigated as a nonthermal alternative to thermal inactivation of microorganisms in liquids. A novel RF system was developed and produced frequencies in the range of 20 kHz to 60 kHz. Electric field strengths of 20 kV/cm and 30 kV/cm were applied to suspensions of Saccharomyces cerevisiae in water over a temperature range of 35 to 55 C. The flow rate was 1.2 l/min. The population of S. cerevisiae was reduced by 2.1 (s.d. 0.1 log) following exposure to a 30 kV/cm field at 40 C. The results of the present study provide the first evidence that RF high electric fields inactivate microorganisms at moderately low temperatures. Increasing the field strength, number of treatments and temperature enhanced inactivation. Frequency had no effect on inactivation over the range of frequencies studied.