Development of enterococci and production of tyramine during the manufacture and ripening of Cheddar cheese

Abstract

The effect of six strains of enterococci (three strains of Enterococcus faecalis, and one strain each of Ec. faecium, Ec. durans and Ec. casseliflavus) on flavour development and tyramine production in Cheddar cheese during manufacture and ripening was studied in two trials. No strain produced gelatinase or haemolysin and all of them grew well during manufacture reaching 107 colony forming units (cfu)/g in 6 h, after which they remained more or less constant during at least 48 weeks of ripening. There was no relationship between tyramine production in a broth containing tyrosine and tyramine production in the cheese. All strains, except Ec. casseliflavus, produced tyramine in the cheese, with the greatest concentration (162 mg/kg) being produced by Ec. durans after 9 months ripening at 8 ºC. There was no statistically significant difference (P > 0.05) between the flavour of the control cheese and any cheese containing an enterococcus. Nevertheless, cheese made with Ec. faecium E-24 received the best score in each trial at both time points. No off-flavours were found. Regarding proteolysis, only Ec. faecalis E-140 showed significant (P < 0.05) increases in both phosphotungstic acid and pH 4.6 soluble N. It is concluded that enterococci have little effect on the flavour of Cheddar cheese.