Published online by Cambridge University Press: 29 January 2008
Lactococcus lactis strain AMP2I expresses OppA(D471R), a mutant oligopeptide binding OppA protein in which the aspartyl residue at position 471 was replaced by arginine. As a consequence of a different peptide transport in this strain, experimental Hispánico cheese made with Lc. lactis AMP2I had a higher content of total free amino acids than control cheese made with Lc. lactis AMP1I, an isogenic strain expressing wild-type OppA (Picon et al. 2005, 2007). In this work higher levels of diketones, hydroxy-ketones and, to a lesser extent, branched chain aldehydes were recorded for experimental cheese compared with control cheese. These differences levelled off as ripening proceeded. Strong correlations support the hypothesis that the increased levels of these volatile compounds in cheese made with Lc. lactis AMP2I are linked to higher concentrations of free amino acids threonine, valine and leucine.
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