The effect of oxidation-reduction potential on the characteristics of UF white cheese produced using single strains of Lactococcus lactis

The effect of oxidation-reduction (redox) potential (ORP) on the composition, viability of starter, and proteolysis of ultrafiltered (UF) white cheese was determined during 90 days of ripening. For the modification of the redox potential of cheese, Na2S2O4 (0.01%, w/w) and KIO3 (0.05%, w/w) were added as reducing or oxidizing agents, respectively, to UF retentate. A single strain of either Lactococcus lactis subsp. lactis CM41 or L. lactis subsp. cremoris UD459 was used as a starter culture. Three different types of cheese were produced for each culture, including control, reduced, and oxidized. The redox environment significantly affected the viability of starter lactococci, the chemical composition, and the proteolysis of cheese samples. During ripening, the redox potentials of the cheeses made with the reducing agent were slightly different than the control cheese (approximately -20 mV lower), while the cheeses made with the oxidizing agent exhibited positive redox potential (ORP +120 mV to +210 mV) during ripening. The starter lactococci in the oxidized cheeses lost their viability after the 60th day of ripening. Reducing conditions (ORP 315 mV to 350 mV) stimulated secondary proteolysis, and this was strain-dependent. These findings support the importance of redox environment on starter activity and accordingly cheese characteristics.