Potential impact on cheese flavour of heterofermentative bacteria from starter cultures

Leuconostoc mesenteroides subsp. cremoris, Leuconostoc pseudomesenteroides and Lactobacillus danicus were grown to early stationary phase in MRS and a cheese based medium (CBM). Lb. danicus had lower aminopeptidase and aminotransferase activity after growth in CBM compared with growth in MRS. Lb. danicus showed aminotransferase activity on all 20 amino acids investigated after growth in CBM; growth in MRS gave higher activities but on fewer amino acids. Highest activity was on aromatic amino acids. Lb. danicus had generally higher and broader aminopeptidase and aminotransferase activity than the Leuconostoc species. When grown in CBM the aminotransferase activity was more similar between Lb. danicus and the leuconostocs. Lb. danicus and Leu. pseudomesenteorides strains had activity on substrates containing short chain fatty acids; activity on C8 and C12 was only seen for the leuconostocs. The results show that the potential role of heterofermentative bacteria in cheese flavour formation involves specific esterase and aminotransferase activities.