Leuconostoc gelidum and Leuconostoc gasicomitatum strains dominated the lactic acid bacterium population associated with strong slime formation in an acetic-acid herring preserve

摘要

Spoilage characterised by strong slime and gas formation affected some manufacture lots of 2 an acetic-acid Baltic herring (Culpea haerengus membras) preserve after few weeks’ storage 3 at 0-6°C. The product consisted of herring filets in acetic acid marinade containing sugar, 4 salt, allspice and carrot slices. Microbiological analyses of the spoiled product showed high 5 lactic acid bacterium (LAB) levels ranging from 4.5 ×108 to 2.4 × 109 CFU/g. Yeasts were 6 not detected in any of the herring samples. Since LAB contaminants seldom are associated 7 with fresh fish, LAB populations associated with marinade ingredients (carrots, allspice) 8 were also analysed. The highest LAB levels exceeding 107 CFU/g were detected in 9 equilibrium modified atmosphere packaged baby carrots whereas the levels detected in the 10 allspice samples did nor exceed 4.3 × 105. A total of 176 randomly selected LAB isolates 11 originating from herring, carrot and allspice samples were further identified to species level 12 using a 16 and 23S rRNA gene RFLP (ribotyping) database. Leuconostoc gelidum and 13 Leuconostoc gasicomitatum strains dominated both in the spoiled herring and carrot samples. 14 These species are heterofermentative producing CO2 from glucose and they also produce 15 dextran from sucrose. Inoculation of some commercial herring products with spoilage- 16 associated L. gelidum and L. gasicomitatum strains verified that these strains have the 17 capability of producing slime and gas in herring preserves although slime formation was not 18 as strong as in the original samples. Since L. gelidum and L. gasicomitatum strains were 19 commonly detected in carrots, carrot slices used for the fish marinade were considered to be 20 the probable source of these specific spoilage organisms. 21