RESUMO
In-plant validation of an alternative washing and sanitizing method was conducted at a cantaloupe packing operation in Mexico. This method consisted of a spray water wash followed by spraying warm (55 to 60 degrees C) 2% (L)-lactic acid solution and was compared with the existing method of spray washing the melons with tap water followed by immersion in a chlorinated water tank. Surface samples (100 cm(2)) were collected from 160 melons subjected to each processing method and tested for counts of aerobic bacteria, coliforms, and Escherichia coli. The aerobic plate counts from cantaloupes washed in the dump tank ranged from 3.6 to 5.2 log CFU/cm(2) and were significantly higher (P < 0.05) than those from melons treated with the alternative spray method, which ranged from 1.8 to 2.6 log CFU/cm(2). Coliform counts for cantaloupes treated in the dump tank were 0.2 to 2.2 log CFU/cm(2) and were below the detection level (-6.0 log CFU/cm(2)) on cantaloupes treated by the spray method. Growth of E. coli was observed in 2.5% of the samples of cantaloupes treated in the dump tank and in none of the samples of cantaloupes treated by lactic acid spray (P < 0.05). These results support the elimination of dump tanks in cantaloupe packing operations established by the Mexican government for certification of firms exporting cantaloupes to the United States. When a sanitizer is to be applied to the product, lactic acid seems to be a viable option, at least for products such as cantaloupes whose quality is not affected by an acid wash.
Assuntos
Cucumis melo/microbiologia , Manipulação de Alimentos/métodos , Embalagem de Alimentos/métodos , Conservação de Alimentos/métodos , Saneamento/normas , Bactérias Aeróbias/isolamento & purificação , Contagem de Colônia Microbiana , Qualidade de Produtos para o Consumidor , Desinfetantes/farmacologia , Manipulação de Alimentos/normas , Embalagem de Alimentos/normas , Conservação de Alimentos/normas , Humanos , Higiene , Ácido Láctico/farmacologia , MéxicoRESUMO
The effect of different washing or sanitizing agents was compared for preventing or reducing surface and internal contamination of tomatoes by Salmonella Typhimurium and Escherichia coli O157:H7. The tomatoes were inoculated by dipping them in a bacterial suspension containing approximately 6.0 log CFU/ml of each pathogen and then rinsing them with tap water, hypochlorite solution (250 mg/liter), or lactic acid solution (2%, wt/vol). All treatments were applied by dipping or spraying, and solutions were applied at 5, 25, 35, and 55 degrees C. With the exception of the lactic acid dip at 5 degrees C, all treatments reduced both pathogens on the surfaces of the tomatoes by at least 2.9 cycles. No significantly different results were obtained (P > 0.05) with the dipping and spraying techniques. For internalized pathogens, the mean counts for tomatoes treated with water alone or with chlorine ranged from 0.8 to 2.1 log CFU/g. In contrast, after lactic acid spray treatment, all core samples of tomatoes tested negative for Salmonella Typhimurium and, except for one sample with a low but detectable count, all samples tested negative for E. coli O157:H7 with a plate count method. When the absence of pathogens was verified by an enrichment method, Salmonella was not recovered from any samples, whereas two of four samples tested positive for E. coli O157:H7 even though the counts were negative. Few cells of internalized pathogens were able to survive in the center of the tomato during storage at room temperature (25 to 28 degrees C). The average superficial pH of tomatoes treated with tap water, chlorine, or lactic acid was 4.9 to 5.2, 4.1 to 4.3, and 2.5, respectively (P < 0.05), whereas no differences were observed in the internal pH (3.6 to 3.7) of the tomatoes treated with different sanitizers. The general practice in the tomato industry is to wash the tomatoes in chlorinated water. However, chlorine is rapidly degraded by organic matter usually present in produce. Therefore, lactic acid sprays may be a more effective alternative for decontaminating tomato surfaces. The use of warm (55 degrees C) sprays could reduce pathogen internalization during washing.
Assuntos
Desinfetantes/farmacologia , Escherichia coli O157/crescimento & desenvolvimento , Ácido Hipocloroso/farmacologia , Ácido Láctico/farmacologia , Salmonella typhimurium/crescimento & desenvolvimento , Solanum lycopersicum/microbiologia , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos dos fármacos , Contaminação de Alimentos/prevenção & controle , Microbiologia de Alimentos , Concentração de Íons de Hidrogênio , Oxidantes/farmacologia , Salmonella typhimurium/efeitos dos fármacos , Temperatura , ÁguaRESUMO
To study the potential of three bacterial pathogens to cross-contaminate orange juice during extraction, normal operation conditions during juice preparation at food service establishments were simulated. The spread of Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes from inoculated oranges to work surfaces and to the final product was determined. The transference of these three bacterial pathogens to orange juice made from uninoculated oranges with the use of contaminated utensils was also studied. Fresh oranges were inoculated with a marker strain of rifampicin-resistant Salmonella Typhimurium, E. coli O157:H7, or L. monocytogenes. Final pathogen levels in juice were compared as a function of the use of electric or mechanical juice extractors to squeeze orange juice from inoculated oranges. Pathogen populations on different contact surfaces during orange juice extraction were determined on sulfite-phenol red-rifampicin plates for Salmonella Typhimurium and E. coli O157:H7 and on tryptic soy agar supplemented with 0.1 g of rifampicin per liter for L. monocytogenes. After inoculation, the average pathogen counts for the orange rind surface were 2.3 log10 CFU/cm2 for Salmonella Typhimurium, 3.6 log10 CFU/cm2 for E. coli O157:H7, and 4.4 log10 CFU/cm2 for L. monocytogenes. This contamination was spread over all utensils used in orange juice squeezing. Mean pathogen counts for the cutting board, the knife, and the extractor ranged from -0.3 to 2.1 log10 CFU/cm2, and the juice contained 1.0 log10 CFU of Salmonella Typhimurium per ml, 2.3 log10 CFU of E. coli O157:H7 per ml, and 2.7 log10 CFU of L. monocytogenes per ml. Contact with contaminated surfaces resulted in the presence of all pathogens in orange juice made from uninoculated oranges. These results give emphasis to the importance of fresh oranges as a source of pathogens in orange juice.