Improvement of the raw milk microbiological quality by ozone treatment

This work studied the ozone gas bubbling effects in the quality of raw milk. Samples of raw milk were collected before and after ozone gas bubbling at 1.5 mg. L^-1 for 5, 10 and 15 minutes. The ozone efficacy was evaluated by microbial reductions of Enterobactereaceae, total mesophilic aerobic (TMA), psychrotrophic, molds and yeast and Staphylococcus sp counts. The assays were carried out by using an experimental design fully randomized and results were statistically evaluated by Tukey test (p 0.05). For milk without ozone sanitation (control sample), the counts of the Enterobactereaceae, mesophilic aerobic, psychrotrophic, molds and yeast and Staphylococcus sp were 2.39; 4.18; 3.01; 2.70; 2.16 log10 CFU.mL^-1, respectively. The ozonation for 5 minutes was not able to reduce the milk microbial counts. In contrast, treatment with ozone for 10 minutes caused significant reduction (p 0.05) of Enterobacteriaceae (0.59 log), molds and yeast (0.25 log) and Staphylococcus sp (0.59 log). After 15 minutes of treatment, microbial inactivation were observed for the 6 groups of microorganisms evaluated, with reductions of 0.96; 0.60; 0.13; 0.48 and 1.02 log cycles for Enterobacteriaceae, mesophilic aerobic, psychrotrophic, molds and yeast and Staphylococcus sp, respectively. Therefore, the use of ozone gas bubbling can be adopted as a milk pre-process aiming to obtain a reduction of the microbial count in raw milk; however, this treatment did not eliminate the milk thermal process requirement.