Non starter lactic acid bacteria biofilms: A means to control the growth of Listeria monocytogenes in soft cheese

The possibility to consider non starter lactic acid bacteria (NSLAB) biofilms as a means to control the growth of Listeria monocytogenes in soft cheeses was evaluated. In particular, the aptitude to form biofilm of four NSLAB strains (Lactobacillus plantarum DSM1055, Lactobacillus casei DSM20011, Lactobacillus curvatus DSM20019 and Lactobacillus paracasei DSM20207) was investigated. All tested strains were able to form biofilm on stainless steel and the highest quantities were produced when NSLAB were present simultaneously (about 6 Log CFU cm−2). Then, experimental cheeses were made in presence of chips containing 7-days NSLAB biofilms and inoculated with L. monocytogenes (about 2 Log CFU g−1). Results demonstrated that NSLAB biofilms can be considered a useful means to delay the growth of L. monocytogenes in soft cheeses: the maximum cell load attained at the stationary phase was about 6 Log CFU g−1 in experimental cheeses against about 7 Log CFU g−1 observed in control samples.