Growth Control of Listeria monocytogenes on Cold-Smoked Salmon Using a Competitive Lactic Acid Bacteria Flora

Abstract

A Lactobacillus sake strain LKE5 and four strains of Carnobacterium piscicola were evaluated as biopreservation cultures to control the growth of Listeria monocytogenes on vacuum-packed, cold-smoked salmon stored at 5 degrees C. All five strains were antilisterial as live cultures in an agar diffusion assay. Cell-free supernatants of two strains of C. piscicola and L. sake LKE5 were also antilisterial because of the production of bacteriocins. The presence of high cell numbers of strains of C. piscicola had no influence on the sensory quality of cold-smoked salmon stored at 5 degrees C, but L. sake LKE5 caused strong sulfurous off-flavors and was rejected as a culture for biopreservation of cold-smoked salmon. A bacteriocin-producing strain of C. piscicola (A9b) initially caused a 7-day lag phase of L. monocytogenes, followed by a reduction in numbers of L. monocytogenes from 10(3) CFU/ml to below 10 CFU/ml after 32 days of incubation, coinciding with the detection of antilisterial compounds. The presence of a nonbacteriocin-producing strain of C. piscicola (A10a) prevented the growth of L. monocytogenes during the 32-day incubation. The growth of L. monocytogenes was strongly repressed on cold-smoked salmon in the presence of C. piscicola A9b and A 10a, respectively. The initial cell numbers of L. monocytogenes that were found on Oxford plates incubated at 25 degrees C reached low maximum cell counts of 10(4) and 2 x 10(3) after 14 and 20 days of storage in mixed culture with C. piscicola A9b and A10a.

Article

“…Toutes les études réalisées en ajoutant artificiellement L. monocytogenes dans du saumon fumé ont montré une croissance importante (2-3 log UFC·g -1 ) de cette bactérie en quelques semaines de conservation sous vide à 4°C, avec une accentuation notable (5-6 log UFC·g -1 ) si le stockage s'effectue à 8°C [14,36]. Cependant, les résultats observés sur des saumons fumés naturellement contaminés sont beaucoup moins alarmants.…”

“…Des préparations commerciales de nisine (Aplin and Barrett Ltd., Trowbridge, Angleterre; Sigma-Aldrich, St. Louis, MO, USA) associée au CO 2 , inhibent la croissance de L. monocytogenes dans le saumon fumé [36,45] mais le conditionnement sous atmosphère modifiée autorise, contrairement au conditionnement sous vide, le déplacement des fines tranches de saumon fumé dans l'emballage, ce qui ne permet pas une présentation adéquate du produit. Le concept de biopréservation repose sur l'ensemencement du saumon par une flore lactique compétitive capable d'inhiber L. monocytogenes au cours de la conservation au froid.…”

Bacteriocin like substance production by Carnobacterium piscicola in a continuous system with three culture broths. Study of antagonism against Listeria monocytogenes on vacuum packaged salmon

“…Other salmon inoculation experiments have also shown a bacteriostatic effect, when different strains of C. piscicola were co-inoculated with L. monocytogenes (10,17), or a simulated smoked fish system (11). The direct inoculation of the crude extract of a bacteriocin will eliminate the inconvenience of the organoleptic changes that take place during growth of the producer strain.…”

Lactic Acid Bacteria and Their Bacteriocins: A Promising Approach to Seafood Biopreservation

“…In contrast, another related species, namely, C. divergens V41 and its divercin V41, only exhibited a bacteriostatic effect on the target microorganism. Two strains of C. maltaromaticum isolated from CSS demonstrated their efficiency to limit the growth of L. monocytogenes in VP CSS during 31 days of storage at 5°C [134]. In a study using vacuum-packed cold smoked rainbow trout, the combination of nisin and sodium lactate injected into smoked fish decreased the count of L. monocytogenes from 3.3 to 1.8 log10 over 16 days of storage at 8°C [135].…”