Effect of Two Selected Probiotic Leuconostoc mesenteroides Bacteriocin-Producing Strains on Biopreservation and Organic Volatile Compounds in Model Cheese During Ripening and Storage

Lactic acid bacteria (LAB) are widely used in food systems; among them, bacteriocin-producing strains have attracted attention for their potential in the biopreservation of dairy products. This study started from the detection of bacteriocin-encoding genes in eight probiotic <i>Leuconostoc mesenteroides</i> subsp. <i>mesenteroides</i> strains, previously isolated, identified, and characterized for antimicrobial activity. Results confirmed the presence of bacteriocin genes across the strains, with Ln.F5 harboring both <i>mesB</i> and <i>lcnA</i> genes, and three other strains, including the Ln.M14 strain, exclusively carrying the <i>lcnA</i> gene. The two strains, Ln.F5 and Ln.M14, were used, in single and mixed cultures, for the first time, as adjunct cultures in a model cheese. Their impact against <i>Listeria</i> spp., <i>Staphylococcus aureus</i>, <i>Escherichia coli</i>, <i>Micrococcus luteus</i>, and <i>Brochothrix thermosphacta,</i> and on volatile organic compounds (VOCs), during ripening and storage, was evaluated. Results showed high viability (9.2 Log CFU/g) of <i>Leuconostoc</i> spp. in model cheese, up to 60 days of storage, and Pulsed-Field Gel Electrophoresis (PFGE) profiles of the re-isolated bacteria confirmed the survival of the added strains. Furthermore, results indicated the inhibition of <i>E. coli</i> and <i>Listeria</i> spp. started from the 15th day of ripening in samples differently inoculated with the two <i>Leuconostoc</i> strains. <i>Listeria</i> spp. was completely inhibited starting from 15 days by Ln.M14, in single culture. The complete inhibition of <i>S. aureus</i>, <i>M. luteus</i>, and <i>B. thermosphacta</i> was detected after 30 days of ripening in samples differently inoculated with Ln.F5 and Ln.M14. The VOC analyses revealed more complex aromatic profiles in samples inoculated with <i>Leuconostoc</i> strains, which, along with the development of cheese eyes, confirmed the effect of the <i>Leuconostoc</i> strains in enhancing quality traits of cheeses.