Significance of low molecular weight nitrogen constituents in cheese milk and of proteinase-negative variants of a Lactococcus lactis subsp. cremoris strain on the production and maturation of Danbo cheese

Abstract

Abstract Danbo cheeses were produced according to a factorial design in order to elucidate the role of two factors on the production and maturation of the cheese. Frozen, defined-strain LD-cultures were used as starters. The LD-cultures were composed of L-type strain(s): Leuconostoc mesenteroides subsp. cremoris or Leuconostoc lactis; D-type strain(s): Lactococcus lactis subsp. lactis biovar. diacetylactis; and O-type strain(s): Lactococcus lactis subsp. cremoris and/or lactis. Three proportions (0, 40 and 80%) of proteinase-negative (prt−) variants of the O-component were incorporated as the first factor and two levels of low molecular 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 role as discriminator for the experimental cheeses, was reduced significantly by increasing the proportion of prt− cells. A linear correlation was established between bitterness scores and early eluting peaks from Sephadex G25 of the water soluble nitrogen fraction (WSNF) of eight selected experimental cheeses. Finally, reverse phase FPLC analysis of these early-eluting peaks from gel filtration showed that the release of hydrophobic peptides was also reduced by addition of LMWN.