In this research, ozone gas was used at concentrations of 2 and 5ppm in different stages of brined ultrafiltered cheese production and then the samples were subjected to microbial and chemical (protein, pH 4.6-SN/TN, TCA-SN/TN, PTA-SN/ TN, fat, monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA)) analyses during ripening. Ozone treatments included: ozonation of concentrate simultaneously with starter inoculation (OA), ozonation of concentrate before starter inoculation (OB), ozonation of concentrate and brine (OC), ozonation of brine (OD) and control (C). Based on the results, the values of the cheese proteolysis products (pH 4.6-SN/TN, TCA-SN/TN, and PTA-SN/TN) and their protein and fat contents significantly (p ≤ 0.05) increased and decreased, respectively, over the ripening period. The level of MUFA also experienced a significant (p ≤ 0.05) decrease until day 35 of the ripening, followed by an increase until the end of the ripening period. The highest levels of pH 4.6-SN/TN, TCA-SN/TN, and PTA-SN/TN were associated with samples OB5, OC5, and OC5, respectively, whereas the control exhibited the lowest values for these parameters. The fat content of the OA5 sample was significantly (p ≥ 0.05) lower than other samples. On most ripening days, ozonation of the samples did not significantly change their MUFA levels. The PUFA content of the treated samples was also variable on different treatment days. The counts of mold and yeast initially increased until day 70 but subsequently decreased until the end of the ripening period. Throughout the ripening period, the mold and yeast counts of the OA5 and OC5 samples were significantly (p ≤ 0.05) lower than the other treatments. As a result, the use of ozone treatment increased the shelf life of the cheese samples and also enhanced the production of products resulting from proteolysis
