ID: 2218

• Title:
  Development of PEF sterilization system for protein-rich liquid foods
  
  Authors:
  

  Kadoya, Ryosuke
  Yan, Bngyu
  Nakamura, Tomohiro

  
  
  Abstract:
  Pulsed electric field (PEF) is a promising method for non-thermal sterilization of liquid foods. There are many reports showing the usefulness of PEF sterilization in batch processing or small flow rate sterilization experiments. However, for the high flow rate processing of 100 L/h or higher required for industrialization, several serious problems such as a decrease in bactericidal effect, spark discharge, adhesion of components to electrodes occur. These problems are mainly due to the fluid velocity distribution in the flow path of the PEF treatment cell. Because the flow velocity near the flow path walls is much lower than in the center of the tube, more electrical energy is received from the repetitive high-power pulses, resulting in localized heating. This not only degrades heat-sensitive food, but also promotes the formation of solidified food ingredients and deposition on the walls of the flow path, triggering spark discharge. Although several treatment cell structures have been proposed so far, a PEF treatment cell for protein-rich foods such as liquid whole egg (LWE) and milk has not been realized. Here, we propose a novel PEF treatment cell and treatment process that can be operated continuously for a long time for liquid whole egg (LWE) and milk, and also verify its sterilization effect. The PEF treatment cell has a structure in which two flat titanium electrodes with a diameter of 80 mm are arranged above and below a resin plate with a thickness of 8 mm with a hole with a diameter of 4 mm. There are gaps between the resin plate and the upper and lower titanium electrodes. Liquid enters the resin pores through the lower gap and exits through the upper gap after being subjected to a high electric field. This is one unit, and multiple units can be connected in series to increase the bactericidal effect. The liquid was propelled by 4 atm. of nitrogen gas added to the liquid reservoir tank, and the flow rate was controlled by the leak valve placed at the flow path outlet. Heating and warming devices were installed before and after the PEF treatment cell in the flow path to enhance the sterilization effect. The flow rate was set to 10 L/h in this paper. Using this system, PEFs of 25 kV/cm and 15 kV/cm were repeatedly applied to milk and liquid eggs, respectively, at 115 Hz for more than 1 hour. In addition, a bactericidal test against Klebsiella aerogenes was performed using the total system, and a 5-digit bactericidal effect was obtained.
  
  Keywords:
  
  
  Refs:
  
  
  Topic 1:
  10. Food safety and food preservation
  
  Topic 2:
  5. Exposure devices and methods