Analysis of the Bioprotective Potential of Different Lactic Acid Bacteria Against Listeria monocytogenes in Cold-Smoked Sea Bass, a New Product Packaged Under Vacuum and Stored at 6 ± 2°C

Abstract

The aim of the work was to monitor the presence of Listeria monocytogenes in cold-smoked fish products (trout, salmon, and sea bass) marketed in Italy. Cold-smoked sea bass is a new product that has not yet been commercialized and was collected from the production facility. Monitoring data have shown that cold-smoked products can be contaminated by L. monocytogenes, the presence of which has been highlighted mainly by enrichment culture (presence in 25 g). The isolated Listeria were serotyped and belonged mainly to low-virulence serotypes (1/2c), followed by serotypes 1/2a, 1/2b, and 4b. Furthermore, considering the ability of L. monocytogenes to grow in these products due to their chemical–physical characteristics (pH > 6.0, Aw > 0.97) and long shelf life at 4°C, an additional aim was to verify the activity of different bioprotective starters, including Lactilactobacillus sakei (LAK-23, Sacco srl, Via Alessandro Manzoni 29/A, 22071 Cadorago, CO, Italy), Carnobacterium spp., Lacticaseibacillus casei (SAL 106), and Lacticaseibacillus paracasei (SAL 211), in cold-smoked sea bass. All starters were bacteriocin producers. For this experiment, smoked sea bass samples were intentionally inoculated with a mixture of three different strains of L. monocytogenes and of each starter culture. After inoculation, the smoked sea bass were vacuum-packed and stored at 6 ± 2°C for 60 days, simulating the typical abuse storage temperature of markets and home refrigerators. At 0, 15, 30, 45, and 60 days, the sea bass samples were analyzed to evaluate the effectiveness of the starters against L. monocytogenes. Listeria monocytogenes growth was prevented only by the addition of the LAK-23 starter. Indeed, at the end of the shelf life, the amount of L. monocytogenes observed was similar to that in the inoculum. Consequently, the use of this starter can allow the inclusion of cold-smoked sea bass or smoked fish products in category 1.3 of Regolamento CE 2073/2005, which are products that do not support the growth of this microorganism. Finally, the activity of the LAK-23 starter did not produce an off flavor or off odor in the smoked sea bass.

Microbial and Physico-Chemical Characterization of Cold Smoked Sea Bass (Dicentrarchus labrax), a New Product of Fishery

“…The level of Enterobacteriaceae in CSF and CSSB at the end of their shelf life is always more than 6-7 log CFU/g, independent of the initial contamination [4,59]. During storage, psychrotrophic Enterobacteriaceae can grow and reach high loads, as demonstrated by Fuentes et al [59].…”

“…Regarding CSF, the Enterobacteriaceae counts are variable but not always significantly different (p > 0.05) [21]. The initial level of contamination seemed to be related to the in-house microbiota and hygienic conditions in the smokehouses rather than to the raw material quality, which always reaches up to 100 CFU/g for fresh fish meat [4,53,58].…”

“…The low levels of TBC at the beginning of storage indicate good fish quality [4,12,56], which could be attributed to the raw material, packaging material, and processing, as demonstrated by Truelstrup Hansen et al [57], who studied the influence of three different smokehouses on the contamination level of vacuum-packed CSS and cold smoked trout (CST). The results showed a significant difference in microbial counts among the three different Danish smokehouses.…”

The biological effect of a beef‐derived Latilactobacillus sakei on beef steaks during chilled storage

“…Moreover, there are often significant application differences between bioprotective strains. In the study of Iacumin et al ( 2021 ) four bioprotective strains inoculated on cold‐smoked sea bass at 5 log CFU/g, and only L. sakei LAK‐23 successfully controlled the growth of L. monocytogenes when the storage reached 60 d. Therefore, it is necessary to evaluate the actual application effect of bioprotective candidate strains in meat.…”

Effects of anaerobic and respiratory adaptation of Lacticaseibacillus casei N87 on fermented sausages production

“…Lactic acid bacteria (LAB) have a long history in the production of several fermented foods. Their growth and metabolic activity can increase the shelf-life and the microbiological safety of certain food products and improve their technological and sensory qualities as well (Comi et al, 2016;Iacumin et al, 2021Iacumin et al, , 2022. In fermented sausages, they are represented mainly by lactobacilli, and they constitute a significant part of the natural microflora along with gram-positive coagulase-negative cocci (CNC) (Rantsiou et al, 2005;Morot-Bizot et al, 2006).…”