RESUMO
Ozone has a broad antimicrobial spectrum and each microorganism species has inherent sensitivity to the gas. The objective of this study was to evaluate the effect of ozone gas on Escherichia coli O157:H7 inoculated on an organic substrate, and the efficacy of ozonated water in controlling the pathogen. For the first experiment, E. coli O157:H7 (ATCC® 43890™) was inoculated in milk with different compositions and in water, which was ozonated at concentrations of 35 and 45 mg L-1 for 0, 5, 15, and 25 min. In the second experiment, water was ozonated at 45 mg L-1 for 15 min. E. coli O157:H7 was exposed for 5 min to the ozonated water immediately after ozonation, and after storage for 0.5, 1.0, 1.5, 3.0, and 24 h at 8 °C. The results showed that the composition of the organic substrate interfered with the action of ozone on E. coli O157:H7. In lactose-free homogenized skim milk, reductions of 1.5 log cycles were obtained for ozonation periods of 25 min at the concentrations tested. Ozonated water was effective in inactivating of E. coli O157:H7 in all treatments. The efficiency of ozone on E. coli O157:H7 is influenced by the composition of the organic substrates, reinforcing the need for adequate removal of organic matter before sanitization. Furthermore, refrigerated ozonated water stored for up to 24 h is effective in the control of E. coli O157:H7.
Assuntos
Escherichia coli O157/efeitos dos fármacos , Viabilidade Microbiana/efeitos dos fármacos , Ozônio/farmacologia , Animais , Bovinos , Contagem de Colônia Microbiana , Escherichia coli O157/crescimento & desenvolvimento , Microbiologia de Alimentos , Leite/microbiologiaRESUMO
The aim of this research was evaluate the efficiency of the action of ozonation of milk on the reduction of the bacterial counts of Staphylococcus aureus artificially inoculated and subjected to different binomials times/concentrations of ozone. The samples were divided in four assays: 1 and 2, with skim milk and ozone concentrations of 34.7 mg L 1 and 44.8 mg L-1, respectively, and assays 3 and 4, with whole milk and the same concentrations of ozone. The time of ozonation in all of the assays was 5 (T1), 10 (T2), 15 (T3), 20 (T4) and 25 (T5) minutes. Each treatment was replicated three times. The bacterial counts were determined immediately before and after the ozonation process by plating the samples on Baird Parker agar. In treatments 1 and 2, the greatest reductions were 0.42 log10 CFU/mL (colony forming units per millilitre), whereas in treatments 3 and 4, the greatest reductions were 0.19 and 0.21 log10 CFU/mL, respectively. The results of all of the tests show that, for T1, there was no reduction in the microbial load, whereas for T2, there was a sharp decrease in the microbiota, and this decrease was even more significant for T4 and T5. In both skim and whole milk with ozone concentrations of 34.7 and 44.8 mg L-1, the reductions were significantly greater after 20 minutes of ozonation. The results indicated that ozone showed low efficacy in the reduction of S.aureus in
O objetivo dessa pesquisa foi avaliar a eficiência do ozônio sobre a redução da contagem de Staphylococcus aureus artificialmente inoculados em leite, utilizando-se diferentes binômios tempo/ concentração. Foram realizados quatro ensaios: 1 e 2, com leite desnatado e concentrações de 34,7 mg L-1 e 44,8 mg L-1 de ozônio, respectivamente; e ensaios 3 e 4, com leite integral nas mesmas concentrações de ozônio. Os tempos de ozonização em todos os ensaios foram de 5 (T1), 10 (T2), 15 (T3), 20 (T4) e 25 (T5) minutos, sendo cada tratamento realizado em triplicata. As contagens bacterianas foram feitas imediatamente antes e após o processo de ozonização das amostras, em agar Baird Parker. Nos tratamentos 1 e 2, as maiores reduções foram de 0,42 log10 UFC/mL, enquanto nos tratamentos 3 e 4, foram de 0,19 e 0,21 log10 UFC/mL, respectivamente. Os resultados de todos os ensaios mostraram que, em T1, não houve redução da carga microbiana, enquanto que a partir de T2, ocorreu uma redução crescente nas contagens, que foi acentuada nos tempos T4 e T5. Tanto para leite desnatado quanto para integral, nas concentrações de 34,7 e 44,8 mg L-1, a partir dos 20 minutos de ozonização, as reduções foram significativamente maiores. Os resultados indicaram que o ozônio apresentou baixa eficácia na redução de S. aureus inoculado em leite fluido e que a gordura do leite interfere na ação bactericida do gá
RESUMO
The aim of this research was evaluate the efficiency of the action of ozonation of milk on the reduction of the bacterial counts of Staphylococcus aureus artificially inoculated and subjected to different binomials times/concentrations of ozone. The samples were divided in four assays: 1 and 2, with skim milk and ozone concentrations of 34.7 mg L 1 and 44.8 mg L-1, respectively, and assays 3 and 4, with whole milk and the same concentrations of ozone. The time of ozonation in all of the assays was 5 (T1), 10 (T2), 15 (T3), 20 (T4) and 25 (T5) minutes. Each treatment was replicated three times. The bacterial counts were determined immediately before and after the ozonation process by plating the samples on Baird Parker agar. In treatments 1 and 2, the greatest reductions were 0.42 log10 CFU/mL (colony forming units per millilitre), whereas in treatments 3 and 4, the greatest reductions were 0.19 and 0.21 log10 CFU/mL, respectively. The results of all of the tests show that, for T1, there was no reduction in the microbial load, whereas for T2, there was a sharp decrease in the microbiota, and this decrease was even more significant for T4 and T5. In both skim and whole milk with ozone concentrations of 34.7 and 44.8 mg L-1, the reductions were significantly greater after 20 minutes of ozonation. The results indicated that ozone showed low efficacy in the reduction of S.aureus in
O objetivo dessa pesquisa foi avaliar a eficiência do ozônio sobre a redução da contagem de Staphylococcus aureus artificialmente inoculados em leite, utilizando-se diferentes binômios tempo/ concentração. Foram realizados quatro ensaios: 1 e 2, com leite desnatado e concentrações de 34,7 mg L-1 e 44,8 mg L-1 de ozônio, respectivamente; e ensaios 3 e 4, com leite integral nas mesmas concentrações de ozônio. Os tempos de ozonização em todos os ensaios foram de 5 (T1), 10 (T2), 15 (T3), 20 (T4) e 25 (T5) minutos, sendo cada tratamento realizado em triplicata. As contagens bacterianas foram feitas imediatamente antes e após o processo de ozonização das amostras, em agar Baird Parker. Nos tratamentos 1 e 2, as maiores reduções foram de 0,42 log10 UFC/mL, enquanto nos tratamentos 3 e 4, foram de 0,19 e 0,21 log10 UFC/mL, respectivamente. Os resultados de todos os ensaios mostraram que, em T1, não houve redução da carga microbiana, enquanto que a partir de T2, ocorreu uma redução crescente nas contagens, que foi acentuada nos tempos T4 e T5. Tanto para leite desnatado quanto para integral, nas concentrações de 34,7 e 44,8 mg L-1, a partir dos 20 minutos de ozonização, as reduções foram significativamente maiores. Os resultados indicaram que o ozônio apresentou baixa eficácia na redução de S. aureus inoculado em leite fluido e que a gordura do leite interfere na ação bactericida do gá
RESUMO
Listeria monocytogenes is a pathogen capable of adhering to many surfaces and forming biofilms, which may explain its persistence in food processing environments. This study aimed to genetically characterise L. monocytogenes isolates obtained from bovine carcasses and beef processing facilities and to evaluate their adhesion abilities. DNA from 29 L. monocytogenes isolates was subjected to enzymatic restriction digestion (AscI and ApaI), and two clusters were identified for serotypes 4b and 1/2a, with similarities of 48% and 68%, respectively. The adhesion ability of the isolates was tested considering: inoculum concentration, culture media, carbohydrate source, NaCl concentration, incubation temperature, and pH. Each isolate was tested at 108 CFU mL⻹ and classified according to its adhesion ability as weak (8 isolates), moderate (17) or strong (4). The isolates showed higher adhesion capability in non-diluted culture media, media at pH 7.0, incubation at 25°C and 37 °C, and media with NaCl at 5% and 7%. No relevant differences were observed for adhesion ability with respect to the carbohydrate source. The results indicated a wide diversity of PFGE profiles of persistent L. monocytogenes isolates, without relation to their adhesion characteristics. Also, it was observed that stressing conditions did not enhance the adhesion profile of the isolates.
Assuntos
Matadouros , Aderência Bacteriana , Proteínas de Bactérias/metabolismo , Microbiologia Ambiental , Regulação Bacteriana da Expressão Gênica , Listeria monocytogenes/isolamento & purificação , Listeria monocytogenes/metabolismo , Carne/microbiologia , Animais , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Brasil , Bovinos , Eletroforese em Gel de Campo Pulsado , Doenças Transmitidas por Alimentos/prevenção & controle , Perfilação da Expressão Gênica , Concentração de Íons de Hidrogênio , Listeria monocytogenes/classificação , Listeria monocytogenes/crescimento & desenvolvimento , Listeriose/prevenção & controle , Viabilidade Microbiana , Tipagem Molecular , Filogenia , Solução Salina Hipertônica , TemperaturaRESUMO
Psychrotrophics microorganisms are able to multiply under refrigeration temperatures. They can produce heat-resistant extracellular enzymes that cause organoleptic and structural changes in milk and dairy products. With the objective of determining the frequency of microorganisms in the dairy process, four farms were evaluated in Londrina city Brazil and different points were assessed. Mesophilic (48hs at 35oC), psychrotrophic (25hs at 21oC) and proteolytic (72hs at 22oC) microorganisms were researched, and the proteolytic predominant microflora were determined by using the Gram stain technique. The main psychrotrophic contamination points were the residual water on milk cans, on bulk tank and bad cleaned teats, and milk cans and teats were the most important sources of proteolytics. Gram negative bacilli represented 69% of the microorganisms in the refrigerated milk that means 45% of the total proteolytics microorganisms in the dairy process. Gram negative bacilli is most frequent on bad cleaned teats, teatcups, residual water in milk cans and bulk tank. The psychrotroph count in the refrigerated milk was more than the mesophilic count, showing that that psychrotrophics are the best indicatator for refrigerated milk contamination. The psycrotrophics count at all points assessed were greater than the ideal limit (10% of the mesophilic count). Thus as refrigeration at 4oC is n
Os psicrotróficos são microrganismos que têm capacidade de multiplicação em temperaturas de refrigeração. Produzem enzimas termorresistentes como proteases e lipases que promovem alterações organolépticas no leite e comprometem a produção de derivados. Com o objetivo de determinar a freqüência desses microrganismos a produção do leite, foram estudadas 04 propriedades da região de Londrina, PR, analisando diversos pontos do processo. Determinou-se a contagem de microrganismos aeróbios mesófilos (48hs a 35ºC), psicrotróficos (25hs a 21ºC), psicrotróficos proteolíticos (72 hs a 22ºC) e as características morfotintoriais da microbiota psicrotrófica proteolítica predominante. Os principais pontos de contaminação por psicrotróficos foram a água residual de latões, tanques de expansão e tetos higienizados inadequadamente, sendo que os psicrotróficos proteolíticos predominam nos latões e tetos. Bacilos Gram negativos representaram 45% da microbiota proteolítica de todo o processo de produção, no leite refrigerado corresponderam a 69% dos psicrotróficos proteolíticos encontrados e ainda predominaram nos tetos higienizados, teteiras, água residual de latões e tanques de expansão. As contagens de psicrotróficos superaram as de mesófilos em leite refrigerado, mostrando que a pesquisa de psicrotróficos é ideal para avaliar a real carga microbiana do leite refrigerado. Como a refrigeração a
RESUMO
Psychrotrophics microorganisms are able to multiply under refrigeration temperatures. They can produce heat-resistant extracellular enzymes that cause organoleptic and structural changes in milk and dairy products. With the objective of determining the frequency of microorganisms in the dairy process, four farms were evaluated in Londrina city Brazil and different points were assessed. Mesophilic (48hs at 35oC), psychrotrophic (25hs at 21oC) and proteolytic (72hs at 22oC) microorganisms were researched, and the proteolytic predominant microflora were determined by using the Gram stain technique. The main psychrotrophic contamination points were the residual water on milk cans, on bulk tank and bad cleaned teats, and milk cans and teats were the most important sources of proteolytics. Gram negative bacilli represented 69% of the microorganisms in the refrigerated milk that means 45% of the total proteolytics microorganisms in the dairy process. Gram negative bacilli is most frequent on bad cleaned teats, teatcups, residual water in milk cans and bulk tank. The psychrotroph count in the refrigerated milk was more than the mesophilic count, showing that that psychrotrophics are the best indicatator for refrigerated milk contamination. The psycrotrophics count at all points assessed were greater than the ideal limit (10% of the mesophilic count). Thus as refrigeration at 4oC is n
Os psicrotróficos são microrganismos que têm capacidade de multiplicação em temperaturas de refrigeração. Produzem enzimas termorresistentes como proteases e lipases que promovem alterações organolépticas no leite e comprometem a produção de derivados. Com o objetivo de determinar a freqüência desses microrganismos a produção do leite, foram estudadas 04 propriedades da região de Londrina, PR, analisando diversos pontos do processo. Determinou-se a contagem de microrganismos aeróbios mesófilos (48hs a 35ºC), psicrotróficos (25hs a 21ºC), psicrotróficos proteolíticos (72 hs a 22ºC) e as características morfotintoriais da microbiota psicrotrófica proteolítica predominante. Os principais pontos de contaminação por psicrotróficos foram a água residual de latões, tanques de expansão e tetos higienizados inadequadamente, sendo que os psicrotróficos proteolíticos predominam nos latões e tetos. Bacilos Gram negativos representaram 45% da microbiota proteolítica de todo o processo de produção, no leite refrigerado corresponderam a 69% dos psicrotróficos proteolíticos encontrados e ainda predominaram nos tetos higienizados, teteiras, água residual de latões e tanques de expansão. As contagens de psicrotróficos superaram as de mesófilos em leite refrigerado, mostrando que a pesquisa de psicrotróficos é ideal para avaliar a real carga microbiana do leite refrigerado. Como a refrigeração a