Autolysis of Lactococcus lactis AM2 stimulates the formation of certain aroma compounds from amino acids in a cheese model

Abstract

The autolysis of Lactococcus lactis starters accelerates the formation of free amino acids during cheese ripening. The purpose of this study was to evaluate the impact of L. lactis autolysis on the conversion of free amino acids to aroma compounds. The study was conducted with two L. lactis isogenic strains differing by their autolytic behaviour in cheese: the highly autolytic strain AM2 and a non-autolytic derivative. The effect of bacterial lysis on phenylalanine catabolism was first evaluated in buffer solution. L. lactis cells were also included in a cheese paste model with or without α-ketoglutarate, which stimulates the first step of amino acid degradation by lactococci. Amino acid catabolism and volatile aroma compound formation were analysed after 28 days of ripening. When α-ketoglutarate concentration was not limiting, autolysis of L. lactis cells stimulated the catabolism of aromatic amino acids and methionine and enhanced the formation of sulphur aroma compounds and benzaldehyde, which are desirable aroma compounds in cheese.