Research On Pulsed Electric Fields Sterilization Mechanism And Experimental Equipment

Recently, consumers' requirements for foods are constantly changing. They demand the foods that are fresh and natural. Therefore, steps used to process foods should be designed to preserve their natural quality. Thermal pasteurization not only kills contaminating microorganisms but also affects the taste, color, and nutritional quality of foods. Cold pasteurization methods have been developed to kill microorganisms without the application of heat. One such method is the use of pulsed electric fields (PEF) for sterilization of liquid foods. The thesis comes from the research of liquid foods normal temperature sterilization technology. The paper briefly discusses the microbial inactivation mechanism in PEF, tentatively gropes for inactivation Models in the certain condition and improves the equipment of PEF sterilization.Recently, sterilization method primarily contains the representation of hot treatment sterilization technology. However, thermal pasteurization not only kills contaminating microorganisms but also affects the taste, color, and nutritional quality of foods, it's hard for hot sensitivity or especial demanded food to expect purpose. Another domain is rising cold sterilization technology , it contains high intensity PEF, ultrasonic sterilization, high-pressure, infrared ray sterilization and pulsed intensity light and so on. The domestic and overseas researchers abroad study PEF sterilization because of easily use characteristic, it will become one of the most promising realization industrialization sterilization methods.With regard to PEF sterilization mechanism, there are lots of hypotheses. It mainly has electrical breakdown, electroporation , electro analysis production effect and ozone effect and so on. This research bases on existing achievements, it observed the shape of bacillus which are treated by PEF using electron microscope. It proved that the bacillus membrane happened fatal breakage. It further proved the membrane was destructived.Through many testings , find out mathematics model of the milk sterilization ratio in the certain conditions. It concluded that the inactive ratio of bacteria associated with the electric intensity and treatment time, the more of electric intensity and treatment time, the higher of inactive ratio. Moreover, the effect of electric intensity to inactive ratio is more distinctive than treatment time.Setting up PEF continuous sterilization equipment. It makes up of pulsed-generator , continuous treatment chambers , oscillograph , liquid food pump and tubes. Thereinto, pulsed-generator and continuous treatment chambers are the key part of the system. They have thecrucial function to sterilization ratio.Using primary pulsed-generator, it had done many proved experiments. Referencing to the domestic and overseas information, it concluded another key factor is waveform. Energy consume ratio of the exponential waveform is less than square waveform's. Its effect is not as good as square waveform. Therefore, it suggested improving primary generator waveform to square waveform. In order to save cost and reduce mistake, it emulated square pulsed generator circuit by using PSB in Matlab. As a result, it gained the waveform that we expected. It provided theory support for further change of the pulsed-generator.