| This thesis is an investigation of the pulsed power treatment system's ability to pasteurize orange juice. Using the hurdle approach, temperature, acidity and number of pulses were varied to maximize the microbial killing. The addition of nisin, lysozyme or both was also investigated. Optimal conditions tested resulted in over six log reductions in the microbial population with 20 pulses of an electric field of 80 kV/cm, at pH 3.5 and a temperature of 44°C with 100 IU nisin/100 mL. The process was most sensitive to the change in temperature (p < 0.0001).; Quality analysis of this juice after treatment showed favourable characteristics. A 97.5% retention of vitamin C was found, along with a 92.7% reduction in pectinmethylesterase activity. The microbial shelf-life was improved and determined to be at least 28 days when stored at 4°C. Gas chromatography analysis revealed no significant differences in aroma compounds before and after pulsing. |
