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Nutritional value of the non-protein N that accumulates during growth of proteinase-positive strains of Lactococcus lactis in milk for dairy lactococcal and leuconostoc isolates

Published online by Cambridge University Press:  01 August 1998

CATHERINE FOUCAUD
Affiliation:
Institut National de la Recherche Agronomique, Unité de Recherches Laitières, F-78350 Jouy-en-Josas, France
SYLVIANE FURLAN
Affiliation:
Institut National de la Recherche Agronomique, Unité de Recherches Laitières, F-78350 Jouy-en-Josas, France
PASCALE BELLENGIER
Affiliation:
Institut National de la Recherche Agronomique, Unité de Recherches Laitières, F-78350 Jouy-en-Josas, France
VINCENT JUILLARD
Affiliation:
Institut National de la Recherche Agronomique, Unité de Recherches Laitières, F-78350 Jouy-en-Josas, France
JEAN RICHARD
Affiliation:
Institut National de la Recherche Agronomique, Unité de Recherches Laitières, F-78350 Jouy-en-Josas, France

Abstract

To estimate the suitability of cultured milk for the subsequent growth of dairy lactic acid bacteria in cheese manufacturing, control milk was first cultured until the end of the exponential phase with one of four proteolytic (Prt+) strains of Lactococcus lactis differing in their proteolytic enzymes, and pasteurized after readjusting the pH to its initial value. Nineteen non-proteolytic (Prt) strains of Lc. lactis and nine Leuconostoc mesenteroides strains of dairy origin were then grown in the precultured milk until the stationary phase and their growth was compared with that in control milk. Despite the accumulation of non-protein N (NPN) during preculture, the growth of most Prt strains of Lc. lactis in precultured milk was either reduced or unchanged whereas that of Ln. mesenteroides strains was unchanged or slightly stimulated. This reduction in growth was reversed by adding an NPN source to precultured milk, indicating that it was due to the exhaustion of assimilable NPN in precultured milk. Thus, preculturing milk with Prt+ strains of Lc. lactis could not be recommended for promoting the subsequent growth of starter cultures in cheese manufacturing.

Type
Research Article
Copyright
Proprietors of Journal of Dairy Research 1998

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