Studio dell’efficacia di colture protettive ed innovazione di processo per garantire la sicurezza alimentare di un formaggio ovino fresco

Listeria monocytogenes (Lm) in foods causes several health and economic issues, increasing the interest in the development of protective cultures able to reduce food contamination risk by pathogens increasing shelf-life without changing their organoleptic characteristics. Some acid lactic bacteria, including Lactobacillus plantarum (Lpl), could inhibit the growth of different pathogenic microorganisms (including Lm) through the secretion of antibacterial peptides known as bacteriocins, the use of which in the food industry, however, remains limited. The research project, in collaboration with Industria Casearia F.lli Pinna s.p.a, was focused on the study and implementation of technological innovations in pathogens growth control in fresh sheep's milk-based cheeses. The experiments were carried out on "Primo sale", a fresh cheese whom characteristics of permissiveness could allow the contamination by altering or pathogenic microorganisms. The listericidal skills of a freeze-dried commercial protective culture containing Lpl strains (Listeria Dairy, Holdbac, Danisco), added during the Primo sale production process, were tested. The listericidal activity carried out by the Pediocin bacteriocin, then the mode of use in vivo and the growth of the protective culture in different matrices were characterized. For the preparation of the inoculum, the scotta, resulting from the production of fresh ricotta cheese, was chosen as the growth substrate. After experimental contamination with Lm strains (Challenge test), of different batches of cheese produced with and without the addition of the protective culture, the effectiveness of Lpl culture itself was assessed. The preliminary results obtained highlight the huge potential of the freeze-dried commercial culture, in reducing the risk of Lm contamination in fresh dairy products.