| The use of elevated temperatures to pasteurize food products leads to a loss of food quality, which has stimulated research into novel non-thermal processes for food preservation. Using non-thermal plasma (NTP) discharges, applied directly into the food product proved effective in reducing the number of Escherichia coli O157:H7 cells in apple juice up to 8 log units. The apple juice used had a pH of 4 and a conductivity of 2.29 mili-Siemen per centimeter (mS/cm).; The pulsed non-thermal plasma system was developed and used to study the effects of different process parameters on the inactivation. The process parameters considered were discharge voltage, pulse number and pulse frequency.; There are no generally accepted models to predict results of non-thermal techniques on cell lethality, a vital aspect of the process optimization of any food preservation technique.; The process parameters found to be most influential in the microbial lethality were pulse frequency and pulse number. A model was developed based on the Weibull distribution and therefore not an expression of inactivation kinetics, but the ‘goodness of fit’ was found to be excellent allowing strong predictive power. These experiments were performed in a batch treatment chamber.; The temperature rise of the sample did not exceed 2.9°C.; A flow through treatment chamber was designed and built for inactivating Escherichia coli O157:H7 in apple juice using pulsed non-thermal plasma. The influence of liquid flow rate was studied and found to affect the cell lethality.; These results aided in a better understanding of the challenges facing design of continuous chambers.; Vitamin C analysis showed that losses are much lower during NTP treatments than those often observed during thermal pasteurization of fruit juices. |
