title: The use of the bacteriocin, nisin, as a preservative in ricotta-type cheeses to control the food-borne pathogen Listeria monocytogenes.
abstract: The efficacy of nisin to control the food-borne pathogen Listeria monocytogenes in ricotta-type cheeses over long storage (70 d) at 6-8 degrees C was determined. Cheeses were prepared from unpasteurized milk by direct acidification with acetic acid (final pH 5.9) and/or calcium chloride addition during heat treatment. Nisin was added in the commercial form of Nisaplin pre-production to the milk. Each batch of cheese was inoculated with 10(2)-10(3) cfu g-1 of a five-strain cocktail of L. monocytogenes before storage. Shelf-life analysis demonstrated that incorporation of nisin at a level of 2.5 mg l-1 could effectively inhibit the growth of L. monocytogenes for a period of 8 weeks or more (dependent on cheese type). Cheese made without the addition of nisin contained unsafe levels of the organism within 1-2 weeks of incubation. Measurement of initial and residual nisin indicated a high level of retention over the 10-week incubation period at 6-8 degrees C, with only 10-32% nisin loss.
authors.affiliation: Technical Services, Aplin & Barrett Ltd, Beaminster, Dorset, UK.
authors.forename: E A
authors.initials: EA
authors.lastname: Davies
authors.forename: H E
authors.initials: HE
authors.lastname: Bevis
authors.forename: J
authors.initials: J
authors.lastname: Delves-Broughton
mesh_terms: D001430:Bacteriocins / Q000494:pharmacology*; D002611:Cheese / Q000382:microbiology* / Q000506:poisoning; D004196:Disease Outbreaks / Q000517:prevention & control; D005069:Evaluation Studies as Topic; D005519:Food Preservation / Q000379:methods; D005520:Food Preservatives / Q000494:pharmacology*; D005517:Foodborne Diseases / Q000453:epidemiology / Q000517:prevention & control; D006801:Humans; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000254:growth & development / Q000472:pathogenicity; D008088:Listeriosis / Q000453:epidemiology / Q000517:prevention & control; D009561:Nisin / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D001430:Bacteriocins; D005520:Food Preservatives; D009561:Nisin