Study On The Kinetics Of Microbial Inactication By Pulsed Electric Fields And Its Application On Orange Juice

Pulsed electric field is an emerging non-thermal technology, through which food can maintain its nutrition to the largest extent. Researches related to PEF have become the hot spot of food industry. And it'd better to make sure the applicability,safety and effectiveness of any new technology before its industrialization.Through utilizing the self-design treatment device for high voltage pulsed electric field pasteurization, firstly, this paper would confirm PEF belonging to non-thermal category of pasteurization without thermal effect. The results showed that under the strongest processing condition, the temperature rose less than 30℃which can prove that PEF is an non-thermal technology.Then this paper analyzed the microbial inactivation under PEF processing. The results showed that different microbial had different sensitivity to PEF. Yeast was sensitive to PEF, while mold was less sensitive to PEF. When increase the number of pulses and the intensity of PEF, the inactivation will rise correspondingly. The different growth stage of microorganism had different sensitivity to PEF. Microorganism in lag stage was much more sensitive to PEF than that of exponential and stationary stage. And microbial in different mediums will have different inactivation. The results showed that low pH mediums will reduce the inactivation of yeast and molds, which will increase the inactivation of bacterium.The kinetics of microbial inactivation by PEF was studied, electric field intensity and treatment time varied from 2．5-20 kV/cm and 170-850μs, respectively. The experimental data showed that different microbial have different critical electric field intensity, the mold was 2．02kV/cm, yeast is 0．339 kV/cm and E.coli was 1．80kV/cm, so it's easy to see that the yeast was much more sensitive to PEF than that of mold and E.coli.Finally,through comparing testing between high voltage electric fields to treat orange juice and conventional heating to treat orange juice by comparing the microorganism inactivation and characteristics of juice. The experimental data showed that PEF cannot kill all the microorganisms in juice, however the number of bacterium was 20 CFU/ml, and the number of yeast and mold was 10 CFU/ml. The storage condition was 0℃, which would help to prolong the shelf-life of juice. During the storage ,the characteristics of orange juice nearly had changes except for some loss of vitamin C. Comparing the two different treated orange juice, the results showed that there were distinguished differences about sensory evaluation between them. It was easy to see that PEF treated orange juice has better taste,flavor and aroma than that of heating treated juice.