Ferreira, Maria Adélia SantosSantos, Maria Isabel da SilvaCavaco, Andreia Filipa de Mendonça Dias2009-07-092009-07-092009http://hdl.handle.net/10400.5/1099Mestrado em Engenharia Alimentar - Instituto Superior de AgronomiaVegetables 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 107 ufc/g psychrotrophs and 2,28 x 106 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 seemsnot 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.porsaladas minimamente processadasmicrorganismos patogénicosanálise microbiológicaELFAminimally processed saladspathgenic microorganismsmicrobiological analysismaster thesis