title: Quantitative and qualitative variability of the caseinolytic potential of different strains of Pseudomonas fluorescens: implications for the stability of casein micelles of UHT milks during their storage.
abstract: Pseudomonas fluorescens grows at low temperature and produces thermo-resistant protease(s) that can destabilize UHT (Ultra High Temperature) milk during its storage. The consequences of contamination of microfiltered milk with 9 strains of P. fluorescens on the stability of the corresponding UHT milk during storage had been investigated in this study. The strains were classified in two groups according to their ability to destabilize UHT milk. For the group of highly destabilizing strains, sedimentations of UHT milks, low values to phosphate test and the presence of aggregates were observed. Zeta potential and hydration of casein micelles decreased, whereas non casein nitrogen (NCN) and non protein nitrogen (NPN) contents increased. The analyses of NCN fraction by liquid chromatography coupled to mass spectrometry indicated that the different casein molecules were hydrolyzed in a similar way for the destabilizing strains suggesting that the same enzyme was implicated. For the group of slightly or not destabilizing strains no visual and biochemical alteration were found. This study showed that destabilization of UHT milk by P. fluorescens was highly variable and strain-dependent.
authors.affiliation: INRA, UMR1253 Science et Technologie du Lait et de l'Œuf, F-35042 Rennes, France.
authors.forename: François
authors.initials: F
authors.lastname: Baglinière
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Tanguy
authors.forename: Julien
authors.initials: J
authors.lastname: Jardin
authors.forename: Aurélie
authors.initials: A
authors.lastname: Matéos
authors.forename: Valérie
authors.initials: V
authors.lastname: Briard
authors.forename: Florence
authors.initials: F
authors.lastname: Rousseau
authors.forename: Benoît
authors.initials: B
authors.lastname: Robert
authors.forename: Eric
authors.initials: E
authors.lastname: Beaucher
authors.forename: Gérard
authors.initials: G
authors.lastname: Humbert
authors.forename: Annie
authors.initials: A
authors.lastname: Dary
authors.forename: Jean Luc
authors.initials: JL
authors.lastname: Gaillard
authors.forename: Caroline
authors.initials: C
authors.lastname: Amiel
authors.forename: Frédéric
authors.initials: F
authors.lastname: Gaucheron
mesh_terms: D000818:Animals; D002364:Caseins / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D061353:Food Storage; D006358:Hot Temperature; D013058:Mass Spectrometry; D008892:Milk / Q000737:chemistry* / Q000382:microbiology*; D011551:Pseudomonas fluorescens / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D002364:Caseins