Influence of milk microbiota on <i>Listeria monocytogenes</i> survival during cheese ripening

Abstract

This study aimed to compare the three strains of <i>Listeria monocytogenes</i> survival in raw milk cheese and pasteurized milk cheese and to suggest the effect of milk microbiota on survival. <i>L. monocytogenes</i> cell counts decreased in all cheese as ripening time increased, and the survival rate was different for the strains of <i>L. monocytogenes</i>. Furthermore, <i>L. monocytogenes</i> survived longer in raw milk cheese than in pasteurized milk cheese. The difference of bacterial survival in each cheese was independent of A_w or the <i>Lactobacillus</i> spp. populations in cheeses; there was no difference in A_w or <i>Lactobacillus</i> spp. populations in all cheeses. The richness of microbiota in raw milk was little higher than in pasteurized milk, and five phyla (Chloroflexi, Cyanobacteria, Deinococcus-Thermus, Lentisphaerae, and Verrucomicrobia) were present only in raw milk. Also, organic acid-producing bacteria were presented more in pasteurized milk compared with raw milk; thus, the growth of <i>L. monocytogenes</i> was slower in pasteurized milk. In conclusion, differences in the microbial community of milk can affect the growth of <i>L. monocytogenes</i>. Making cheese using raw milk is a risk of <i>L. monocytogenes</i> infection; thus, efforts to prevent growth of <i>L. monocytogenes</i> such as the use of appropriate food additives are required.