against pathogens as oleuropein activated by β-glucosidase has very
strong protein-denaturing, protein-crosslinking, and lysine-alkylating
activities (Konno et al., 1999). It has been described that the bactericidal
effect of phenolic compounds is related to alterations in cell wall and cytoplasmic
membrane which could led to the disruption of the cell envelope.
Oleuropein promotes disruption of the peptidoglycan, which can
lead to cell death by destruction of the cell envelope. These changes
occur between 30 and 60 min of incubation in oleuropein supplied as
a pure compound in the growth medium (Rodríguez et al., 2009). The
fatty acid composition is altered in the presence of acidic phenols in
terms of what occurs in response to low temperature or high alcohol
concentration (Rozès and Peres, 1998).
Olives of both cultivars fermented by OSC in reduced salt brines contain
increased amounts of total phenolic compounds (Table 1) and significantly
higher population (p b 0.05) of LAB compared with industrial
processed ones (Table 4). The low salt concentration in olive brines and
flesh contributes to the survival of high population of LAB during fermentation
(Leal-Sánchez et al., 2003). Initial inocula of E. coli O157
EDL-932 and L. monocytogenes Scott A of 7 or 6 log CFU/ml were
inactivated after 24 and 8–10 h, respectively, in olive homogenate
held at 30 °C (Figs. 1 & 2). This is due to the combined effect of all phenolic
substances present in olive pulp which is ultimately responsible
for their antibacterial effect as well as to the antimicrobial activity of
the inoculated OSC. The inactivation of
L. monocytogenes Scott A in the
olive homogenate of industrial processed black Kalamata olives and
green olives Chalkidikis after 8 and 2 h, respectively, is due to the high
salt concentration (4.2–4.1% w/v), the low pH values (4.13–4.50)
and the bactericidal phenolics present as well as to the fact that