Bacterial strain and culture conditions The pure lyophilized starter mixed culture LH100, commonly used in hard cheese production (containing L. helveticus and L. delbrueckii spp lactis), employed in this work was supplied by Distribuidora Alcatraz (Mexico). The culture was transferred twice in MRS broth under aerobic conditions and maintained at 37°C. After 24 h, the microorganisms were harvested by centrifugation at 9000 rpm and 4 °C for 10 min. The cell pellets were washed thrice and resuspended in a saline solution. Finally, the cells were enumerated by the spread plate method using MRS agar and were incubated at 37 °C for 48 h. The final cell concentration was adjusted to 109 CFU/mL.