Searching potential candidates for development of protective cultures: Evaluation of two Lactobacillus strains to reduce Listeria monocytogenes in artificially contaminated milk

RUÍZ, FRANCESCA; BARBERIS, LUCILA; GARCÍA, MARÍA J.; PASCUAL, LILIANA; ASURMENDI, PAULA

JOURNAL OF FOOD SAFETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2019 vol. 40

0149-6085

The aims of this work were (a) to select the minimum concentrations of twobacteriocin-producing lactobacilli strains to reduce Listeria monocytogenes growth inwhole milk, (b) to evaluate the individual and combined application of these chosenlactobacilli concentrations as protective culture in this food and, (c) to estimate iflactobacilli growth caused undesirable changes in the visible characteristics of milk.The selected minimum lactobacilli concentration with antilisterial activity was106 CFU ml−1 for both lactobacilli. Although a high initial concentration of L. monocytogenes(104 CFU ml−1) was added to milk, a notable reduction on listerial counts(2?4 log CFU ml−1) was achieved in comparison to the control. These lactobacillishowed a good adaptability in milk reaching optimal counts and not causing undesirablevisible changes. In conclusion, the use of these lactobacilli could be consideredas a bio-strategy potentially effective to limit the contamination by L. monocytogenesin certain milk-derived products.1 | INTRODUCTIONMilk and dairy products are an important part of daily nutrition in differentage groups. These foods are highly susceptible to contaminationby both nonpathogenic and pathogenic bacteria (Mehmeti,Bytyqi, Muji, Nes, & Diep, 2017). Among them, Listeria monocytogenesis a relevant pathogenic microorganism that causes listeriosis inhumans and several animal species. In fact, dairy products have beenlinked to numerous outbreaks of listeriosis as well as sporadic cases,being responsible for more than 50% of listeriosis outbreaks (CDC,2013; Melo, Andrew, & Faleiro, 2015). Despite the fact that an adequatepasteurization procedure should eliminate L. monocytogenesfrom these foods, there are currently still reports of listeriosis outbreaksassociated with both pasteurized and unpasteurized dairyproducts (Pricope-Ciolacu, Nicolau, Wagner, & Rychli, 2013). Moreover,there are consumer groups in some countries that, followingnaturist philosophy, demand both raw milk and dairy products producedfrom unpasteurized