Production of succinate from citrate by Lb. plantarum

Succinic acid has an acidic, salty/bitter, taste and contributes to savoury flavour of cheese; Emmental cheese contains approximately 0.8-1.4 g succinate/kg. Succinate may be produced from citrate by Lactobacillus plantarum via a reductive tricarboxylic acid pathway (see below). Lb. plantarum is a component of the non-starter lactic acid bacterial (NSLAB) flora of many cheeses.

However, succinate is not usually found in Cheddar at concentrations above its taste threshold (~37 ppm). This may be because (i) strains of Lb. plantarum in NSLAB may not be able to use pathway, (ii) not enough organisms and/or (iii) other citrate-positive microorganisms outcompete Lb. plantarum.

Further reading:

Dudley, EG and Steele, JL (2005). Succinate production and citrate catabolism by Cheddar cheese nonstarter lactobacilli. J. Appl. Microbiol. 98, 14-23.