Avaliação da multiplicação de salmonella spp. em carne de frango exposta a condições isotérmicas e não isotérmicas

A produção avícola representa grande impacto na economia brasileira, já que o país lidera atualmente a exportação de carne de frango. A qualidade e segurança do produto a nível do consumidor depende de esforços em diferentes setores, envolvendo toda a cadeia de produção e fazendo uso de ferramentas robustas de gestão de segurança de alimentos. A microbiologia preditiva permite descrever o comportamento de microrganismos em matrizes específicas de alimentos expostas a condições diferentes, como: temperatura, pH, pressão, entre outros. Nesse estudo, amostras de carne crua de frango e pele foram contaminadas artificialmente com um pool de Salmonella spp. com objetivo de avaliar a multiplicação microbiana em diferentes temperaturas. O pool era composto por cinco sorovares que representam os sorovares de maior importância para indústria avícola brasileira. Modelos Primários e Secundários foram desenvolvidos através do armazenamento sob condições isotérmicas. Os resultados não mostraram multiplicação a 5°C. A 7, 15, 25, 37 e 45°C as fases lag foram 103,86±15,59h, 6,95±2,27h, 1,99±0,47h, 0,55±0,43h e 0,96±0,39h, respectivamente. A população final e o tempo para obter a máxima concentração de Salmonella foram 4,90±0,08 UFC/g em 317 h (7°C); 7,5±0,08 UFC/g em 72 h (15°C); 9,19±0,07 UFC/g em 31 h (25°C); 8,52±0,10UFC/g em 15 h (37°C); 7,63±0,11UFC/g em 12 h (45°C). O modelo secundário foi adequado para descrever a multiplicação de Salmonella em qualquer temperatura entre 7 e 45°C, apresentando bom ajuste com coeficiente de determinação e erro médio da raiz quadrada de 0,97 e 0,029, respectivamente. A modelagem dinâmica da multiplicação de Salmonella foi validada através de experimento em condições não-isotérmicas através da simulação de um cenário de abuso de temperatura, apresentando uma boa performance (RMSE de 0,18, Viés de 1,11 e Acurácia de 1,26). Deste modo, o modelo desenvolvido neste estudo foi adequado para predizer a multiplicação de Salmonella em combinação de carne e pele de peito de frango cru.Chicken production represents great impact in Brazilian economy, as the country leads world exports. Product quality and safety at consumer level depends on efforts among different sectors involving the entire production chain and using robust food safety management tools. Predictive microbiology allows to describe microorganism’s behavior in a specific food matrix exposed to different conditions, as temperature, pH, pressure, among others. In this study, raw chicken breast meat-skin samples were artificially contaminated with Salmonella spp. pool in order to evaluate bacteriological growth at different temperatures. The pool consisted of five Salmonella serovars which represent the most important serovars for Brazilian chicken industry. Primary and Secondary models were developed through storage under isothermal conditions. Results showed no growth at 5°C. At 7, 15, 25, 37 and 45°C lag times were 103.86±15.59h, 6.95±2.27h, 1.99±0.47h, 0.55±0.43h e 0.96±0.39h, respectively. Final population and time to reach maximum Salmonella concentration were 4.90±0.08 CFU/g in 317 h (7°C); 7.5±0.08 CFU/g in 72 h (15°C); 9.19±0.07 CFU/g in 31 h (25°C); 8.52±0.10CFU/g in 15 h (37°C); 7.63±0.11CFU/g in 12 h (45°C). Secondary model was suitable to describe Salmonella growth in any temperature between 7 and 45°C, well-adjusted with determination coefficient and root mean square error of 0.97 and 0.029, respectively. Dynamic modeling of Salmonella growth was validated through non-isothermal conditions in an extreme time-temperature abuse scenario, displaying an overall good performance (RMSE of 0.18, Bias of 1.11 and Accuracy of 1.26). Hence, the developed model for Salmonella spp. is suitable to predict growth in raw chicken breast meat-skin combination exposed to temperatures ranging from 7 to 45 ºC

Assessing the growth of Staphylococcus aureus and Escherichia coli on fruits and vegetables

Introduction: The number of registered foodborne diseases involving fresh produce is a preoccupation in many countries. For this reason, the aim of this study was to better understand the growth of Staphylococcus aureus and Escherichia coli, two indicators of hygienic and sanitary conditions, on fruits and vegetables that were exposed at different temperatures. Methodology: The main salads served at the buffets of commercial restaurants were artificially contaminated with separate pools of both pathogens and subsequently exposed at 10, 20 and 30 °C and at different time intervals. Then, the growth potential of S. aureus and E. coli on each fruit and vegetable was determined. Results: There was no significant S. aureus and E. coli growth on all evaluated foods exposed at 10 °C until 6 hours. When comparing both microorganisms, E. coli demonstrated higher growth potential than S. aureus on all analysed salads. Peculiarly, E. coli had the highest growth rate for the tomato (α = 6.43 at 30 °C), a fruit with low pH. Conclusion: We suggest that fruits and vegetables should be distributed at temperatures equal to or lower than 10 °C and should not be kept for more than 2 hours at room temperature

Enzymatic clarification of orange juice in continuous bed reactors : fluidized-bed versus packed-bed reactor

In this study, a commercial enzyme cocktail designed for fruit juice clarification was immobilized on chitosan beads activated with glutaraldehyde and used for setting-up continuous packed-bed and fluidized-bed reactors. Firstly, the enzyme cocktail concentration in the immobilization process was tested to get maximum biocatalyst activity in the reaction. Then, the effect of pH and temperature on the free and immobilized enzyme cocktail stability and activity were studied. Despite the low enzyme cocktail activity recovery after immobilization (1 %), the stability of immobilized enzyme was greater compared to free enzyme, even under extreme reaction conditions. For example, when activity was measured at 90 °C and pH 4.8, the immobilized enzyme cocktail retained 80 % of its initial activity while the free enzyme retained only 35 %. Finally, the clarification capacity of the biocatalysts using orange juice was tested, providing clearer juices when performed in the fluidized-bed reactor, showing 60 % of its initial clarification capacity after 72 h of continuous use. Otherwise, the clarification rate in the packed-bed reactor decreased linearly during 54 h, probably due to the formation of dead zones and preferential paths along the bed. Pectinase immobilized on chitosan particles and used in fluidized-bed reactor seems to be a good alternative for large scale application on juice clarification