Fröder Hans, Martins Cecília Geraldes, De Souza Katia Leani Oliveira, Landgraf Mariza, Franco Bernadette D G M, Destro Maria Teresa
Departamento de Alimentos e Nutrição Experimental, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Av. Professor Lineu Prestes 580, BL 14, 05508-900 São Paulo, São Paulo, Brazil.
J Food Prot. 2007 May;70(5):1277-80. doi: 10.4315/0362-028x-70.5.1277.
The increasing demand for fresh fruits and vegetables and for convenience foods is causing an expansion of the market share for minimally processed vegetables. Among the more common pathogenic microorganisms that can be transmitted to humans by these products are Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella. The aim of this study was to evaluate the microbial quality of a selection of minimally processed vegetables. A total of 181 samples of minimally processed leafy salads were collected from retailers in the city of Sao Paulo, Brazil. Counts of total coliforms, fecal coliforms, Enterobacteriaceae, psychrotrophic microorganisms, and Salmonella were conducted for 133 samples. L. monocytogenes was assessed in 181 samples using the BAX System and by plating the enrichment broth onto Palcam and Oxford agars. Suspected Listeria colonies were submitted to classical biochemical tests. Populations of psychrotrophic microorganisms >10(6) CFU/g were found in 51% of the 133 samples, and Enterobacteriaceae populations between 10(5) and 106 CFU/g were found in 42% of the samples. Fecal coliform concentrations higher than 10(2) CFU/g (Brazilian standard) were found in 97 (73%) of the samples, and Salmonella was detected in 4 (3%) of the samples. Two of the Salmonella-positive samples had <10(2) CFU/g concentrations of fecal coliforms. L. monocytogenes was detected in only 1 (0.6%) of the 181 samples examined. This positive sample was simultaneously detected by both methods. The other Listeria species identified by plating were L. welshimeri (one sample of curly lettuce) and L. innocua (2 samples of watercress). The results indicate that minimally processed vegetables had poor microbiological quality, and these products could be a vehicle for pathogens such as Salmonella and L. monocytogenes.
对新鲜水果、蔬菜以及方便食品需求的不断增加，正促使最低限度加工蔬菜的市场份额不断扩大。这些产品可传播给人类的较为常见的致病微生物包括单核细胞增生李斯特菌、大肠杆菌O157:H7和沙门氏菌。本研究的目的是评估一系列最低限度加工蔬菜的微生物质量。总共从巴西圣保罗市的零售商处采集了181份最低限度加工叶类沙拉样本。对133份样本进行了总大肠菌群、粪大肠菌群、肠杆菌科、嗜冷微生物和沙门氏菌的计数。使用BAX系统并通过将富集肉汤接种到Palcam和牛津琼脂平板上，对181份样本进行了单核细胞增生李斯特菌的评估。疑似李斯特菌菌落进行了经典生化试验。在133份样本中，51%的样本嗜冷微生物数量>10⁶CFU/g，42%的样本肠杆菌科数量在10⁵至10⁶CFU/g之间。97份（73%）样本中粪大肠菌群浓度高于10²CFU/g（巴西标准），4份（3%）样本中检测到沙门氏菌。两份沙门氏菌阳性样本的粪大肠菌群浓度<10²CFU/g。在所检测的181份样本中，仅1份（0.6%）检测到单核细胞增生李斯特菌。该阳性样本通过两种方法同时检测到。通过平板接种鉴定出的其他李斯特菌属包括韦氏李斯特菌（一份卷心莴苣样本）和无害李斯特菌（两份西洋菜样本）。结果表明，最低限度加工蔬菜的微生物质量较差，这些产品可能是沙门氏菌和单核细胞增生李斯特菌等病原体的传播媒介。
