Abstract
The aim of this work was to study the presence of Listeria monocytogenes, as well as the potential activity of two bioprotective cultures (Lyocarni BOX-74 and Lyocarni BOX-57), versus a mix of three L. monocytogenes strains that were intentionally inoculated in cooked cubed ham, packaged in Modified Atmosphere Packaging and stored at different temperatures. The bioprotective cultures limit L. monocytogenes growth in cubed cooked ham stored either at 4 °C for 60 days and at 4 °C for 20 days and at 8 °C for 40 days. The inhibition at 8 °C is particularly useful for industrial cooked meat products, considering there are often thermal abuse conditions (8 °C) in the supermarkets. Both the starters can eliminate L. monocytogenes risk and maintain the products safe, despite the thermal abuse conditions. In addition, both culture starters grew without producing perceptible sensory variations in the samples, as demonstrated by the panel of the untrained tasters. The bioprotective LAB produced neither off-odours and off-flavours, nor white/viscous patinas, slime, discoloration or browning. Therefore, according to the obtained data, and despite the fact that cooked cubed ham did not show pH ≤ 4.4 or aw ≤ 0.92, or pH ≤ 5.0 and aw ≤ 0.94, as cited in the EC Regulation 2073/2005. It can be scientifically stated that cubes of cooked ham with the addition of bioprotective starters cultures do not constitute a favourable substrate for L. monocytogenes growth. Consequently, these products can easily fall into category 1.3 (ready-to-eat foods that are not favourable to L. monocytogenes growth, other than those for infants and for special medical purposes), in which a maximum concentration of L. monocytogenes of 100 CFU g−1 is allowed.
Highlights
Listeria monocytogenes can cause fatal disease (30–40%) in foetuses, infants, pregnant women, elderly subjects and immunocompromised individuals with cancer, kidney disease, heart disease or AIDS; subject to organ transplants; and/or treated with immunosuppressants [1,2,3]
One hundred and eighty (180) samples of cooked cubed ham, placed in Modified Atmosphere Packaging (MAP) of 100 g of product produced by 3 Italian factories (60 each), were collected from local supermarkets and analysed in an epidemiological study to evaluate the frequency of the presence of L. monocytogenes
The study demonstrated the presence of Listeria monocytogenes in cooked cubed ham (Table 2)
Summary
Listeria monocytogenes can cause fatal disease (30–40%) in foetuses, infants, pregnant women, elderly subjects and immunocompromised individuals with cancer, kidney disease, heart disease or AIDS; subject to organ transplants; and/or treated with immunosuppressants [1,2,3]. The level of this accidental contamination is usually low, at less than 10 CFU g−1 or cm−2 [18,22,31,33] Despite this low initial concentration, sliced or diced cooked ham can represent a risk for consumers, because L. monocytogenes can reach high concentrations during their shelf lives at 4 ◦C of 30 and 60 days, respectively. Since the use of plant and animal extracts can often change the smell, taste and texture of food [45], there has been an increase in the direct use of bacteriocins with antimicrobial effects or bioprotective cultures, because of their antagonistic effect and production of organic acids or bacteriocins against L. monocytogenes [46,47] These bacteriocin inhibition effects are likely caused by different actions, such as competition for nutrients, as well as organic acid and bacteriocin production, in addition to the “hurdle” parameters. Strains of Lactobacillus sakei, L. casei, L. brevis, L. curvatus, L. plantarum and Carnobacterium spp. isolated from meat products frequently
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