Ozonation of the pasteurized skim milk to extend the shelf life: evaluation of the chemical and microbial properties

Today, the desire to use ozone as a strong antimicrobial compound, cost-effective, and eco-friendly innovation, has increased to increase the shelf life of food products. This study was conducted in order to evaluate the chemical and microbial properties of thermally pasteurized skim milk treated with pressurized ozone injection at concentrations of zero, 1.5, 5, and 10 ppm. The chemical, microbial and sensory characteristics of the treated milk samples were evaluated on days 0, 4, 7 and 15 of storage in the refrigerator. The total viable count (TVC) in the treated samples with ozone compared to the control had a noticeable decrease in all storage days. The highest antimicrobial effect was observed on the 15th day of storage with 10 ppm ozone and the lowest effect was observed on the 4th day with 1.5 ppm ozone. However, there was no significant difference in pH (6.8-6.88) and acidity (0.16-0.18) between treated and control samples. Although the peroxide number (PV) in the treated samples and the control samples was higher than the standard, but its reduction was evident in the treated samples compared to the control samples. Also, by comparing the sensory characteristics among the samples, no significant differences were observed. In general, treatments with 5 and 10 ppm ozone had the best efficiency in increasing the shelf life of pasteurized milk. According to the results, ozone can be used as an auxiliary method to increase the effectiveness of thermal processes in pasteurization and increase the shelf life of milk.