Inhibitory effects of flavor compounds on Staphylococcus aureus WRRC B124

Acetanisole (4'-methexyacetophenone) (AC), benzaldehyde (BE), cinnamaldehyde (CI), diacetyl (DI), phenylpropionaldehyde (PH), and pyruvaldehyde (PY) were tested against growth of S. aureus WRRC B124 in brain heart infusion broth. Activity was assessed in the presence and absence of oxygen at 12, 19 and 37C, and in combination with mild (20 min at 50 or 60C) heat treatments. The carbonyl compounds limited S. aureus growth at minimal inhibitory concentrations (MIC) of less than or equal to 0.5-8.0 mM. After 4 h at 37C, a 2 to 3-log10 CFU/ml population reduction was observed with cultures containing 8.0 mM PH, PY, DI or CI. Activity was O2-tension independent, with CI (0.5 mM), DI (2.0 mM) and PY (2.0 mM) being most active. The MIC for CI was temperature independent, while PY was most effective at 19C, and PH and DI at 12C. Mild heat treatment of carbonyl-supplemented samples reduced previously observed MICs. At 60C, for example, the MICs for AC and BE, 4.0 and 8.0 mM respectively, were both reduced to less than or equal to 0.5 mM. The decimal reduction times for S. aureus exposed to both UV-light and 8 mM flavor compounds were 3.3 and 4.3 s for CI and DI, respectively. However, the other compounds were not as effective in the presence of UV since the decimal reduction times ranged from 7.7 to 9.0 s. The carbonyl compounds tested were effective antistaphylococcal agents and their use in combination with thermal processing may serve as a new approach to control S. aureus growth and other gram-positive foodborne pathogens