Under the industrial conditions, a ripening rennet cheese was manufactured with a dash of saltpetre added to the brine instead to the milk. The cheese manufactured as described above was microbiologically and organolepticly evaluated. Control cheese samples, manufactured both with no saltpetre and with saltpetre added, served as a material for comparison. It was stated that the Swiss and Dutch cheese types, manufactured using a modified method with nitrates(V) added, showed a good microbiological quality. The colia bacteria and the butter fermentation bacteria were inhibited in their growth. The ripe Gouda I cheeses, manufactured by a modified method of applying KNO₃, had the counts of coli bacteria and of spore-forming bacteria at the same level, i.e. absent in a 10^-1 g solution. The results obtained in the case of the ripe cheese of the Tykociński type were similar. The ripe Gouda II cheeses showed a worse microbiological quality compared to Gouda I and Tykocinski cheeses. The count of the spore-forming bacteria was: absent in 10^-1 g, however, the counts of the coligroup bacteria ranged from 10^-2 to 10^-4 g. Nevertheless, all the cheeses manufactured with the use of the modified method with saltpetre applied were more often classified as cheeses of higher quality. And the control chesses manufactured using nitrates added to milk designed for cheese were more often disqualified (i.e. regarded as out of ‘class’).