title: Shelf life extension of ricotta cheese using coatings of galactomannans from nonconventional sources incorporating nisin against Listeria monocytogenes.
abstract: Shelf life extension of Ricotta cheese was evaluated at 4 degrees C upon the use of edible coatings made of galactomannans from Gleditsia triacanthos incorporating nisin against Listeria monocytogenes. Three different treatments were tested in cheese: samples without coating; samples with coating without nisin; and samples with coating containing 50 IU x g(-1) of nisin. To test the effectiveness of the treatments against L. monocytogenes, the surface of the cheese was inoculated with a suspension of the microorganism. Microbiological and physical-chemical analyses of the cheese samples were performed during 28 days. Results showed that the cheese coated with nisin-added galactomannan film was the treatment presenting the best results in terms of microbial growth delay (p < 0.05). The addition of nisin also affects (p < 0.05) the physical and mechanical properties of the films: O(2) permeability decreased from 1.84 to 1.35 x 10(-12) cm(3) x (Pa x s x m)(-1); CO(2) permeability increased from 1.96 to 6.31 x 10(-12) cm(3).(Pa x s x m)(-1); opacity increased from 3.68 to 4.59%; tensile strength ranged from 0.84 to 1.46 MPa; and elongation at break improved from 50.93 to 68.16%. These results demonstrate that novel galactomannan-based edible coatings, when combined with nisin, may provide consumer-friendly alternatives to reduce L. monocytogenes postcontamination on cheese products during storage.
authors.affiliation: Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Joana T
authors.initials: JT
authors.lastname: Martins
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Cerqueira
authors.forename: Bartolomeu W S
authors.initials: BW
authors.lastname: Souza
authors.forename: Maria do
authors.initials: Md
authors.lastname: Carmo Avides
authors.forename: António A
authors.initials: AA
authors.lastname: Vicente
mesh_terms: D002611:Cheese / Q000032:analysis* / Q000382:microbiology; D005519:Food Preservation / Q000379:methods*; D005520:Food Preservatives / Q000494:pharmacology*; D005690:Galactose / Q000031:analogs & derivatives; D031501:Gleditsia / Q000378:metabolism; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000254:growth & development; D008351:Mannans / Q000378:metabolism / Q000494:pharmacology*; D009561:Nisin / Q000494:pharmacology*
chemical_list: D005520:Food Preservatives; D008351:Mannans; C012990:galactomannan; D009561:Nisin; D005690:Galactose