Microbiological quality of ready-to-eat street foods in Lisbon, Portugal

Abstract

Street food sector is an important component of the food distribution system in many cities. However, foods exposed for sale on the roadside are generally associated with conditions that favors its potential microbiological contamination. In this study, the microbiological quality of 118 ready-to-eat street foods sold in the metropolitan area of Lisbon, Portugal was evaluated. Mesophilic aerobic bacteria, yeasts, moulds, Enterobacteriaceae and Escherichia coli were used as spoilage/hygiene indicators. Listeria monocytogenes, Salmonella spp., coagulase-positive staphylococci (CPS), Clostridium perfringens, Bacillus cereus and E. coli pathotypes implicated in gastrointestinal disease were used as food safety/hygiene indicators. Thirty-five (29.7%) of the samples were classified as satisfactory, 29 (24.6%) as questionable and 51 (43.2%) as unsatisfactory. Three samples (2.6%) were unsatisfactory/ potentially dangerous, due to the presence of the L. monocytogenes > 102 cfu/g and/or B. cereus > 105 and/or CPS > 104. B. cereus genes encoding causative toxins were detected in the strains isolated from two samples containing > 105 cfu/g. Salmonella spp., Clostridium perfringens and pathogenic E. coli were not detected in any of the examined samples. CPS was detected in 26.3% of the samples.A significant relationship between microbiological quality and food groups, with the increase of questionable and unsatisfactory classifications for those samples including raw components, like fruits and vegetables, was observed (Fisher-Freeman-Halton = 29.01, p < 0.001). The obtained data highlights for the need of education and training of street-food vendors to improve the food safety management system in the place of sale.