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

      Rea, Mary; Franz, C.M.A.P.; Holzapfel, W.H.; Cogan, Tim; European Union; CT97-3078 (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)
      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.
    • Partitioning of starter bacteria and added exogenous enzyme activities between curd and whey during Cheddar cheese manufacture

      Doolan, I. A.; Nongonierma, Alice B.; Kilcawley, Kieran; Wilkinson, M.G.; Department of Agriculture, Food and the Marine, Ireland; 04/R&D/C/238 (Elsevier, 26/07/2013)
      Partitioning of starter bacteria and enzyme activities was investigated at different stages of Cheddar cheese manufacture using three exogenous commercial enzyme preparations added to milk or at salting. The enzyme preparations used were: Accelase AM317, Accelase AHC50, Accelerzyme CPG. Flow cytometric analysis indicated that AHC50 or AM317 consisted of permeabilised or dead cells and contained a range of enzyme activities. The CPG preparation contained only carboxypeptidase activity. Approximately 90% of starter bacteria cells partitioned with the curd at whey drainage. However, key enzyme activities partitioned with the bulk whey in the range of 22%–90%. An increased level of enzyme partitioning with the curd was observed for AHC50 which was added at salting, indicating that the mode of addition influenced partitioning. These findings suggest that further scope exists to optimise both bacterial and exogenous enzyme incorporation into cheese curd to accelerate ripening.