author(s)
Zina Saab Khudhir and Mazin Raad Mahmood

abstract
In the present study, thirty raw milk samples were collected randomly from different stores and retailer markets in Baghdad province to evaluate the effect of ozone treatment at a concentration of 0.5 ppm on the bacteriological quality (Total aerobic bacteria, Coliforms and Staphylococcus aureus counts). The current study was also planned to investigate the effects of ozonation treatment on the shelf life of raw milk after 24hrs of storage at both refrigeration (4 °C) and the ambient temperatures (30 °C). Data revealed that there were significant (P<0.0001) differences in the percentage of microorganisms that affect the raw milk quality, where the highest prevalence were found in the total aerobic bacteria and Coliforms (100%) respectively followed by the Staph. aureus (60%). The microorganisms that affect the raw milk quality (aerobic bacteria, Coliform, and Staph. aureus) showed a different sensitivity to the ozone treatment at 0.5 ppm for 10, 15 and 20 minutes at different storage temperatures (ambient and refrigeration temperatures). The highest microbial counts that were found in the control milk samples indicated that most of these samples were produced under very poor hygienic conditions. The bacterial counts reduction in raw milk samples after exposure to ozonation treatment for 10, 15 and 20 minutes was not enough for improving both the quality and the shelf life of raw milk.