SIGNIFICANCE OF LOW-MOLECULAR-WEIGHT NITROGEN CONSTITUENTS IN CHEESE MILK AND OF PROTEINASE-NEGATIVE VARIANTS OF A LACTOCOCCUS-LACTIS SUBSPCREMORIS STRAIN ON THE PRODUCTION AND MATURATION OF DANBO CHEESE

Danbo cheeses were produced according to a factorial design in order t o elucidate the role of two factors on the production and maturation o f the cheese. Frozen, defined-strain LD-cultures were used as starters . The LD-cultures were composed of L-type strain(s): Leuconostoc mesen teroides subsp. cremoris or Leuconostoc lactis; D-type strain(s). Lact ococcus lactis subsp. lactis biovar. diacetylactis; and O-type strain( s): Lactococcus lactis subsp, cremoris and/or lactis. Three proportion s (0, 40 and 80%) of proteinase-negative (prf) variants of the O-compo nent were incorporated as the first factor and two levels of low molec ular weight nitrogen constituents (LMWN) in cheese milk (-/+ addition of 0.15%, w/v) as the second factor. Physiological characteristics of the starter were studied. The specific proteinase activity was reduced about 50% by the addition of LMWN. Bitterness, which played a key rol e as discriminator for the experimental cheeses, was reduced significa ntly by increasing the proportion of prt(-) cells. A linear correlatio n was established between bitterness scores and early eluting peaks fr om Sephadex G25 of the water soluble nitrogen fraction (WSNF) of eight selected experimental cheeses. Finally, reverse phase FPLC analysis o f these early-eluting peaks from gelfiltration showed that the release of hydrophobic peptides was also reduced by addition of LMWN.