ESTUDO DA INFLUÊNCIA DE PSICROTRÓFICOS AERÓBIOS E DE ...

Abstract
STUDY THE INFLUENCE OF AEROBICS PSYCHROTROPHS AND
ENTEROBACTERIACEAE IN LISTERIA MONOCYTONEGES 1/2a and 4b SURVIVAL ON
MINIMAL PROCESSED SALADS
Vegetables natural state is susceptible of spoilage. Search for products that contain natural
ingredients and are ready-to-eat has increased. The aim of this thesis was to study the
growth/survival of Listeria monocytogenes in samples of minimally processed salads from
Portuguese supermarkets.
To evaluate the presence and concentration of psychrotrophs, Enterobacteriaceae,
Escherichia coli, Aeromonas hydrophila, Clostridium perfringens, Bacillus cereus and
L. monocytogenes, classic microbiological analysis was carried. But Enzyme-linked
Fluorescent Assay was used to detect Salmonella spp., E. coli O157H7 and
L. monocytogenes.
The average contamination of salad was of 2,44 x 10 7 ufc/g psychrotrophs and 2,28 x 10 6
ufc/g Enterobacteriaceae. Listeria monocytogenes was detected in one salad
corresponding to 1,5 % contamination. Simulating conditions, its growth potential risk was
evaluated in twenty seven samples, spiked with serovares 1/2a and 4b, by counts until the
sell-by-date. To evaluate the sensorial alterations undergone, organoleptic tests were
performed by a taste panel.
Salad samples studied do not support the growth of L. monocytogenes and this fact seems
not to related with the number and consortium of the native micro flora found. Results of the
sensorial analysis had indicated the occurrence of sensible organoleptic alterations during
the period of storage.
Keywords: Minimally processed salads, pathogenic microorganisms, microbiological
analyses, ELFA.
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