Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Agricultural and Biosystems Engineering

First Advisor

K. Muthukumarappan


Effectiveness of ozone for inactivating Listeria monocytogenes in ready-toeat cooked and cured ham was studied for three different ozone environments namely, gaseous phase, aqueous phase and humidified (>90%) phase. The effectiveness was studied for all environments at 3 different ozone concentrations (0.2, 0.5 & 1.0 ppm), 3 different exposure times (1, 15 & 30 min) and 2 different temperatures (10 & 20°C). The study was conducted under controlled temperature using a continuous ozone concentrator-generator (OZ BTU by corona discharge) and a Plexiglas sample treatment chamber. Maximum microbial inactivation (as% kill of Listeria monocytogenes) achieved was 90% at 20°C for 30 min exposure using the gaseous environment followed by the aqueous (44.2%) and humidified (36.8%) phase. The effectiveness increased with increasing exposure time, temperature and ozone concentration. The samples exposed to gaseous environment at 20°C were also analyzed for physical characteristics of color and peak load. Results indicate that interactions of free radicals with organic matter may affect the color characteristics of the ham. However, peak load characteristics remained unaffected. Based on this study results, the synergistic effect of ozone and Microgard® 300 was investigated. The survival rate of Listeria monocytogenes was studied as a function of gaseous ozone concentration (0, 1.0, 2.0, 3.0 ppm), Microgard®300 (0, 1.0, 2.0, 3.0% ), temperature (10, 15, 20°C) and storage period (0, 1, 5, 1 0 days) for a fixed treatment period of 30 min and storage temperature of 4°C. From the results, a combination of ozone between 0.2-0.5 ppm, Microgard®300 between 1.0-2.0% and storage period up to 5 days can inactivate up to 99.0% of Listeria monocytogenes on cooked and cured ham. The temperature did not show any significant effect on %kill of Listeria monocytogenes. There was no synergistic effect of ozone and Microgard®300 for controlling Listeria monocytogenes in cooked and cured ham.


South Dakota State University



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