In order to verify the antimicrobial activity of NEW in controlling
cross-contamination of spoilage bacteria during washing steps,
we contaminated lettuce leaves with a spoiler pseudomonas strain.
Leaves were let to dry three hour before proceeding with NEW
washing. Results of dipping treatments on trocadero lettuce, not
previous subject to disinfection treatments, with NEW on the
Fig. 2. Effect of neutral electrolyzed water produced by tap water (NEW), sodium chloride (NEW þ NaCl) or sodium bicarbonate solution (NEW þ NaHCO3), and the sodium chloride
and sodium bicarbonate un-electrolyzed solutions, against three Pseudomonas strains after 2 min of contact at 4 C. Values represent microbial population surviving after different
treatments (average values ± SD; N ¼ 3). Differences among average values related to the same strain subjected to different treatment were indicated by different letters when
found significantly different (P 0.05) after calculation of the Fisher's LSD value.
L. Pinto et al. / Food Microbiology 50 (2015) 102e108 105
control of total mesophilic bacteria, Pseudomonadaceae and the
spoilage bacteria P. chicorii I3C are shown in Table 1. Samples
inoculated with P. chicorii I3C presented, before washing, levels of
APC and Pseudomonas spp. higher than 5 log cfu/g. Our data show
that the inoculum of P. chicorii I3C didn't influence the level of APC
in the inoculated lettuce samples. NEW treatment reduced of about
1 log cfu/g APC in contaminated leaves, confirming the data obtained
by dipping treatments of un-inoculated fresh cut vegetables
(section 3.3). After 3 days of cold storage leaves inoculated with
spoiler bacteria showed level of APC higher than control samples.
Starting from the third day of cold storage, APC not differed among
un-inoculated and inoculated lettuce. Pseudomonas spp. count of
lettuce dipped in contaminated water was higher than lettuce
washed in sterile tap water of about 10 times, confirming viability
of spoilage microbial cells after 3 h from dipping. Disinfection with
NEW resulted in the same Pseudomonas spp. count as that recorded
for APC. At the third day of cold storage Pseudomonas spp. counts of
inoculated lettuce were higher than control samples, suggesting
the psychrotrophic behavior of P. chicorii I3C. Kinetics growth of
total mesophilic bacteria and Pseudomonadaceae have shown the
same development during cold storage, so it could indicate that
total bacterial population could be mainly constituted by the
genera Pseudomonas. As concerns browning symptomps recorded
during cold storage of lettuce leaves, all samples scored 3 from the
6th day of storage. The preserving effect of NEW in reducing