The current study was designed with three replications to study the effects of ozone gas on the microbial load of yogurt prepared from ozone treated milk at 0, 40, 60 and 70 ppm concentrations for 10 minutes and stored at refrigerator (5±1˚c). Staph. aureus, coliforms and mold counts of the samples were studied at the 1st, 2nd, 3rd , 5th and 7th day of storage.
The results showed that Ozone gas decreased microbial load of yogurt samples, the lowest and the highest counts of microbial load were detected in samples treated with concentration of 70 ppm of Ozone gas and control respectively. Results showed that Ozone gas increased the shelf - life of yogurt samples vs. the control samples. In addition, the sensory analysis
revealed that zone gas at the concentrations of 40, 60 and 70 ppm had no adverse effects on the yogurt sensory quality.