RESUMEN
This study was conducted to determine the concentration and optimal treatment time of chlorine for reducing feline calicivirus (FCV) and murine norovirus (MNV) as surrogates of norovirus (NoV) on stainless steel surfaces and to develop a predictive inactivation method using a response surface methodology. The reduction levels of FCV VR-782 and MNV on stainless steel surfaces after treatment with various concentrations of chlorine (0 to 5,000 ppm) for various times (0 to 5 min) were measured. The reduction values of both FCV and MNV on stainless steel surfaces after 5,000 ppm of chlorine treatment for 5 min were 5.20 TCID(50) per coupon. The predictive results obtained by central composite design were analyzed by standard analysis of variance. The application of multiple regression analysis was related to the following polynomial equations: (i) FCV (log TCID(50) per coupon) = -0.3714 + 0.8362x(1) + 0.0011x(2) + 0.0001x(1)x(2) - 0.1143x(2)(1) -0.0001x(2)(2) (x(1), time; x(2), concentration) and (ii) MNV (log TCID(50) per coupon) = + 0.0471 + 0.0807x(1) + 0.0011x(2) + 0.0001x(1)x(2) -0.0910x(2)(1) -0.0001x(2)(2) (x(1), time; x(2), concentration). It was concluded that these polynomial equation models of reduction of FCV and MNV could be used to determine the minimum concentration of chlorine and exposure times to control human NoV on food contact surfaces.
Asunto(s)
Cloro/farmacología , Desinfectantes/farmacología , Contaminación de Alimentos/prevención & control , Norovirus/efectos de los fármacos , Acero Inoxidable , Calicivirus Felino , Recuento de Colonia Microbiana , Relación Dosis-Respuesta a Droga , Humanos , Viabilidad Microbiana , Norovirus/crecimiento & desarrollo , Factores de TiempoRESUMEN
Cross-contamination to fruit and vegetables can readily occur through contaminated surfaces; thus, there is a need to develop methods to inactivate microorganisms on the surfaces of various materials. The aim of this study was to develop methods to reduce the levels of Escherichia coli on the surfaces of various materials and to develop a predictive model as a function of chlorine concentration and exposure time. The reduction of E. coli on the surfaces of stainless steel, plastic, wood, rubber, glass, and ceramic at various chlorine concentrations (0-200 ppm) after a 0-5-min exposure was evaluated. The surface treatment at the maximum chlorine concentration (200 ppm) over a 5-min exposure reduced the E. coli contamination levels to 5.30, 5.18, 3.34, 4.69, 5.05, and 5.53 log CFU/cm(2) on the surfaces of stainless steel, plastic, wood, rubber, glass, and ceramic, respectively. Using these results, predictive models for the reduction of E. coli on surfaces of various materials using chlorine treatment were developed. Each model was significant (p<0.05) and defined as fit by the lack of fit and probability of normal residuals. It has measured the R(2) value to 0.9746. Therefore, the models presented in this study could be used to determine the minimum concentrations of chlorine and exposure times needed to control E. coli on the surfaces of various materials.
Asunto(s)
Cloro/farmacología , Utensilios de Comida y Culinaria/normas , Desinfectantes/farmacología , Escherichia coli/crecimiento & desarrollo , Contaminación de Alimentos/prevención & control , Análisis de Varianza , Cerámica , Recuento de Colonia Microbiana , Relación Dosis-Respuesta a Droga , Escherichia coli/efectos de los fármacos , Vidrio , Humanos , Viabilidad Microbiana , Modelos Biológicos , Plásticos , Goma , Acero Inoxidable , Factores de Tiempo , MaderaRESUMEN
Cronobacter sakazakii cells in biofilms formed on silicone, polycarbonate, and stainless steel coupons immersed in reconstituted powdered infant milk formula were treated with ethanol (10 to 70%) and UV light (12 to 2,160 mW.s/cm(2)) as antibacterial treatments. Biofilm maturation curves were determined after immersion at 25 degrees C for up to 144 h. Populations increased after subsequent immersion at 25 degrees C for 24 h in reconstituted powdered infant milk formula to the respective maximum levels of 7.96, 7.91, and 6.99 log CFU per coupon. Populations attached to silicone and polycarbonate surfaces to a greater extent than to stainless steel (P < 0.05). Treatment with 10% ethanol did not cause a significant decrease in the level of C. sakazakii, but treatment with 30, 40, and 50% ethanol reduced the levels to approximately 1.73, 3.02, and 4.17 log CFU per coupon, respectively. C. sakazakii was not detected on any coupon after treatment with 70% ethanol or 2,160 mW.s/cm(2) UV light. A synergistic effect of sequential ethanol and UV treatments was not observed.
Asunto(s)
Biopelículas/crecimiento & desarrollo , Cronobacter sakazakii , Etanol/farmacología , Contaminación de Alimentos/análisis , Alimentos Infantiles/microbiología , Rayos Ultravioleta , Adhesión Bacteriana/fisiología , Recuento de Colonia Microbiana , Seguridad de Productos para el Consumidor , Cronobacter sakazakii/efectos de los fármacos , Cronobacter sakazakii/fisiología , Cronobacter sakazakii/efectos de la radiación , Microbiología de Alimentos , Humanos , Lactante , Fórmulas Infantiles , Recién Nacido , Cemento de Policarboxilato , Siliconas , Acero Inoxidable , Propiedades de Superficie , Temperatura , Factores de TiempoRESUMEN
This study was performed to develop a predictive model for the growth rate of Bacillus cereus in cooked rice. A response surface methodology (RSM) was used with a combination of storage temperature (10 to 40 degrees C) and pH value (5.4 to 6.8). The growth curves generated under different conditions were fitted using a modified Gompertz equation, and the relationship of the growth rate to the growth curves was modeled using an RSM quadratic polynomial equation. The predictive model was significant (P < 0.01), and the predicted values of the growth parameters obtained using the model equations were in close agreement with experimental values (R2 = 0.9864). The RSM evaluation for describing the growth rate of B. cereus involved both a bias factor (Bf) and an accuracy factor (Af). Both the Bf value (1.006) and the Af value (1.011) approached 1.0 and were within acceptable ranges. Therefore, the adequacy of the predictive model for B. cereus in cooked rice was verified by the validation data.