Intermittently delivered pulsed electric fields for sterile storage of turbid media

This paper introduces a new concept and method for long-term sterile storage of turbid product, which is potentially subject to microbial contamination. The method uses intermittent delivery of pulsed electric fields (IDPEF) throughout the storage at time intervals that are prescribed according to microorganisms' growth kinetics. This new approach facilitates sterile storage without the need for chemical preservatives, additives, radiation or the complex infrastructure demanded by refrigeration. Unlike ultraviolet radiation, IDPEF can be used in turbid media. The first part of this paper is a theoretical discussion on the growth kinetics of microorganisms treated by IDPEF. We then provide a preliminary experimental study on the kinetics of microorganism growth in a turbid microbial growth media as a function of the IDPEF delivery intervals. Last, we demonstrate the use of the method using milk as a medium. IDPEF of 30 pulses, 17.5 kV/cm field strength, 40 μ long, 1 Hz delivered every 12 h was found to have the ability to preserve milk in a non-sterile environment at room temperature as effectively as refrigeration at 4 °C. The method has many obvious applications in biotechnology, the food industry, and is of particular importance with regard to geographical areas lacking refrigeration for storage of pharmaceuticals and food. This study was performed on the laboratory scale and a substantial adaptations are required in order to apply it to the industrial scale.