3.1. Microbial growth kinetics in tryptic soy broth
Growth curves of bacteria measured at an OD of 600 nm are
shown in Fig. 1. For E. coli O157:H7 ATCC 43895 (Fig. 1A), the
treatment with a combination of LAE, EDTA and CO showed no
growth over 12 h and had a significantly lower OD than other
treatments except the one with a combination of LAE and EDTA
(Fig. 1A). For S. Enteritidis (Fig. 1B), the combination of LAE, EDTA
and CO also prevented growth followed by the combinations of LAE
and EDTA, and CO and EDTA. Similarly, the triple antimicrobial
combination showed the highest efficiency inhibiting the growth of
L. monocytogenes Scott A (Fig. 1C) although the bacterium did
demonstrate growth with this treatment after 7e8 h. Overall,
antimicrobial activities of the combination of LAE, EDTA and CO
were significantly better than treatments with double or single
antimicrobials, which indicated potential of synergistic effect
among LAE, EDTA and CO.