In this work the effects of addition of different amounts of sodium chloride, during cheese making, on shelf life of mozzarella cheese were evaluated. The mozzarella cheese quality decay was assessed during storage at 9 °C by monitoring microbiological, sensory and physico-chemical changes in the product. Results showed that Pseudomonas spp. growth was responsible for cheese unacceptability, whereas the sensory quality did not limit cheese shelf life. In particular, the highest shelf life values were obtained for mozzarella without salt and with the lowest salt concentration (0·23 g NaCl), and amounted to about 5 and 4 d, respectively. On the contrary, high salt concentrations affected product shelf life, probably as a consequence of progressive solubilisation of cheese casein, due to the phenomenon of ‘salting in’.