Application of Ozone for the Reduction of Microorganisms Present in Raw Cow and Buffalo Milk Samples

Abstract

The aim of this study was to investigate the effect of ozone gas on the total bacterial counts as well as on some Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) and the Gram negative bacteria (E.coli and Salmonella enteritidis) in milk samples of cow and buffalo. Milk samples (1L) were inoculated with specific quantities of each bacteria then they were exposed to ozone gas at a concentration of 100mg ozone gas/10 min/L of milk for durations of 10, 20, 30, 40, 50, and 60 minutes. Then the viable bacterial cell counts were determined using the pour plate method. Results showed that bacterial counts were reduced as the exposure time to ozone gas was increased and the highest killing rate of bacterial was observed after 60 minutes of exposure. Results also indicated that the bacterial killing rate percentage was higher in cow milk samples compared to buffalo milk samples for all the bacteria tested, suggesting that the chemical composition of milk has a clear impact on the effectiveness of ozone gas in terms of the bacterial killing rate. Generally, the bacteria killing rate reached 63.4 to 90.6% in cow milk, while it reached 59.7 to 75.1% in buffalo milk samples after 60 min of exposure.