Inhibition of Listeria innocua in cheddar cheese by addition of nisin Z in liposomes or by in situ production in mixed culture.
The effect of addition of purified nisin Z in liposomes to cheese milk and of in situ production of nisin Z by Lactococcus lactis subsp. lactis biovar diacetylactis UL719 in the mixed starter on the inhibition of Listeria innocua in cheddar cheese was evaluated during 6 months of ripening. A cheese mixed starter culture containing Lactococcus lactis subsp. lactis biovar diacetylactis UL719 was selected for high-level nisin Z and acid production. Experimental cheddar cheeses were produced on a pilot scale, using the selected starter culture, from milk with added L. innocua (10(5) to 10(6) CFU/ml). Liposomes with purified nisin Z were prepared from proliposome H and added to cheese milk prior to renneting to give a final concentration of 300 IU/g of cheese. The nisin Z-producing strain and nisin Z-containing liposomes did not significantly affect cheese production and gross chemical composition of the cheeses. Immediately after cheese production, 3- and 1.5-log-unit reductions in viable counts of L. innocua were obtained in cheeses with encapsulated nisin and the nisinogenic starter, respectively. After 6 months, cheeses made with encapsulated nisin contained less than 10 CFU of L. innocua per g and 90% of the initial nisin activity, compared with 10(4) CFU/g and only 12% of initial activity in cheeses made with the nisinogenic starter. This study showed that encapsulation of nisin Z in liposomes can provide a powerful tool to improve nisin stability and inhibitory action in the cheese matrix while protecting the cheese starter from the detrimental action of nisin during cheese production.
Benech
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Dairy Research Centre STELA, Université Laval, Québec, Canada G1K 7P4.
Kheadr
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Laridi
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Lacroix
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Fliss
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D002611:Cheese / Q000382:microbiology*; D015169:Colony Count, Microbial; D003470:Culture Media; D005285:Fermentation; D005516:Food Microbiology; D013294:Lactococcus lactis / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D008081:Liposomes / Q000494:pharmacology*; D008087:Listeria / Q000187:drug effects* / Q000254:growth & development; D008854:Microscopy, Electron; D009561:Nisin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*
D003470:Culture Media; D008081:Liposomes; D009561:Nisin; C071364:nisin Z