Proteolysis and formation of volatile compounds in cheese manufactured with a bacteriocin-producing adjunct culture

Abstract

Hispánico cheese, a semi-hard Spanish variety, was manufactured from a mixture of pasteurized cows' and ewes' milks (4[ratio ]1) using a commercial mesophilic LD-type starter comprising Lactococcus lactis subsp. cremoris, Lc. lactis subsp. lactis, Lc. lactis subsp. lactis var diacetylactis and Leuconostoc mesenteroides subsp. cremoris. Varying amounts (0–1·0 g/kg) of an Enterococcus faecalis INIA 4 culture in milk were added as a bacteriocin-producing adjunct. Differences in pH between cheeses manufactured with and without the bacteriocin producer did not exceed 0·11 pH units. Starter lactococci lost viability more rapidly in cheeses made with the bacteriocin producer, which reached counts of up to 6×10⁷ cfu/g during ripening. Aminopeptidase activity in 1-d-old cheese made from milk inoculated with 1·0 g bacteriocin-producing culture/kg was twice that in control cheese. Degrees of overall proteolysis and levels of total free amino acids in 45-d-old cheese made with 1·0 g bacteriocin-producing culture/kg were 1·80-fold and 2·17-fold those in control cheese of the same age. Inoculating milk with 1·0 g/kg bacteriocin-producing culture reduced the level of hydrophobic peptides in the resultant cheese, increased the concentrations of 3-methyl-1-butanal, diacetyl and acetoin, and resulted in the highest scores for flavour quality and flavour intensity throughout ripening.