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Advisor(s)
Abstract(s)
During the last decades food borne outbreaks associated with consumption of raw vegetables have been
increasing and green leafy vegetables seem to be the most frequently implicated products.
In order to determine the microbial quality and the incidence of the major food borne pathogens in
Minimally Processed (MP) salads commercialized in Portugal, a survey was conducted in Lisbon Retail
Markets, from July 2007 to August 2008, to determine microbial contamination loads and identify
potential pathogenic bacteria.
A total of 151 samples were purchased from 2 supermarkets: 38 romaine lettuce, 12 various spinach
and 101 mixed salads with three or four different ingredients. The samples were tested for aerobic
psychotropic micro-organisms (APM), Enterobacteriaceae, Escherichia coli, Listeria spp., presumptive
Bacillus cereus, Aeromonas hydrophila and Clostridium perfringens counts as well as for presence of
Salmonella spp., Listeria monocytogenes and E. coli O157. Samples were also evaluated for taste quality.
The results showed that APM counts of romaine lettuce and mixed salads had a similar median,
respectively, 6.2 and 6.5 log cfu/g and mixed spinach had the highest one (7.6 log cfu/g). The median
value found for Enterobacteriaceae was 5.44 log cfu/g. Only four samples showed positive result for E. coli
(2.65%) but just one (0.8%) had a slightly higher load of contamination. Although the percentage and
levels of contamination loads were low, these mustn’t be ignored, for the reason that the strains in three
of the samples belong to VTEC group (1.99%). E. coli O157, Salmonella spp. and C. perfringens weren’t
detected in any sample. For the enumeration of Listeria spp., two samples (1.32%) had presence of Listeria
innocua and L. monocytogenes had an incidence of 0.66%. A. hydrophila was identified in 11 samples
(7.28%), and in 8 of them with considerable counts (>105). Contamination with B. cereus was found in
22.7% of samples analyzed, though in small numbers, which doesn’t represent a major concern to food
safety. All isolated strains were assessed for its potential toxin production and it was found that 40% of
these strains had this ability. Results from sensory panel showed organoleptic differences in salads
during its shelf-life period
Description
Available at ScienceDirect
Keywords
minimally processed salads bacterial pathogens sensory analysis quality evaluation
Pedagogical Context
Citation
"Food Control". ISSN 0956-7135. 23 (2012) 275-281