Reduction of Pseudomonas Inoculated into Whole Milk and Skin Milk by Ozonation

Milk is one of the most consumed foods in the world by owning in its composition carbohydrates, proteins, lipids, vitamins and minerals. However, these intrinsic characteristics make it an excellent substrate for microbial growth. The contaminating microbiota of milk is usually composed of psychrotrophic microorganisms, especially the species of Pseudomonas that multiply well at refrigeration temperatures and produce thermos-resistant enzymes, which compromise the quality of milk. The aim of this study was to evaluate the efficiency of ozonation of milk on the reduction on artificially inoculated Pseudomonas. The samples were divided in two groups: whole and skim milk. Five brands of whole milk and five brands of skim milk were tested, experimentally divided into control groups, contaminated groups and contaminated and exposed to ozonation groups. The time and concentration of ozonation in both assays were 5, 10 and 15 min and 28 mgL−1. The results showed reduction of 1 log and 4 logs of Pseudomonas after 5 and 10 min of ozonation respectively, in both whole and skim milk (p > 0.05). After 15 min of ozonation the reduction of microorganisms was significantly higher for skim milk in relation to whole milk (p < 0.05). The results indicated that the effectiveness of the microbial reduction promoted by ozonation in samples of whole milk and skim milk contaminated with Pseudomonas is time and milk composition dependent. Therefore, according to our results the substrate composition interferes with the bactericidal action of the ozone.