Ripening conditions: A tool for the control of Listeria monocytogenes in uncooked pressed type cheese

The effect of ripening conditions (two temperatures, 9 °C and 13 °C, and two relative humidities 93% and 97%) on the growth of Listeria monocytogenes and other microbial populations was evaluated in the cores and rinds of uncooked pressed type cheeses prepared with pasteurised milk and inoculated either with Streptococcus thermophilus only or with an anti-listerial consortium. Regardless of temperature and relative humidity (RH), inhibition by the anti-listerial consortium was stronger in the cheese cores than in the rinds. Temperature had no significant effect on L. monocytogenes counts in cores or rinds. However, at the beginning of ripening in the consortium cheese, L. monocytogenes growth was more strongly inhibited at 13 °C than at 9 °C. Regardless of inoculation type and ripening temperature, counts of L. monocytogenes were significantly lower in the cores and rinds of cheeses ripened at 93% than at 97% RH. Lactobacilli counts were higher at 13 °C than at 9 °C and at 93% than at 97% RH. Lactobacilli can help to inhibit L. monocytogenes by catabolising galactose and producing lactate. Further investigations will be needed to evaluate the effect of ripening at 13 °C and 93% RH on the sensorial properties of cheese.