Behavior of Yersinia enterocolitica and Salmonella typhimurium in Crottin goat's cheese.

In order to evaluate the behavior of Yersinia enterocolitica and Salmonella typhimurium in Crottin goat's cheese, inoculated products stored at 5, 15 and 25 degrees C were analysed together with chemical and microbiological characteristics of the cheese. In general, low counts of microorganisms were detected. None of the samples showed the presence of Escherichia coli, Salmonella spp. or Y. enterocolitica. In the inoculation tests, Y. enterocolitica and S. typhimurium were inhibited during storage; nevertheless, these bacteria survived for extensive periods. The counts at the end of the experiments at 5 and 15 degrees C were high, indicating that contamination with high bacterial numbers represents a potential health hazard. The primary mathematical models used to analyse the behavior of Y. enterocolitica and S. typhimurium were the Vitalistic, Gompertz's empirical and Churchill's model. The mean square error was calculated for the three models in order to evaluate the goodness-of-fit of each one. For Y. enterocolitica, the Vitalistic model was the best at the three temperatures. For S. typhimurium, there was no significant difference between the three models at 5 and 15 degrees C; the Churchill model was clearly the best at 25 degrees C. These results confirm that, in order to predict the risk of transmission of pathogenic microorganisms in foods using mathematical models, it is essential to analyse their behavior in specific foods.

Evaluation of Petrifilm method for enumerating aerobic bacteria in Crottin goat cheese.

The Petrifilm Aerobic Count Plate (ACP) developed by 3M laboratories, is a ready-to-use culture medium system, useful for the enumeration of aerobic bacteria in food. Petrifilm was compared with a standard method in several different food products with satisfactory results. However, many studies showed that bacterial counts in Petrifilm were significantly lower than those obtained with conventional methods in fermented food. The purpose of this study was to compare the Petrifilm method for enumerating aerobic bacteria with a conventional method (PCA) in Crottin goat's cheese. Thirty samples were used for the colony count. The mean count and standard deviation were 7.18 +/- 1.17 log CFU g(-1) on PCA and 7.11 +/- 1.05 log CFU g(-1) on Petrifilm. Analysis of variance revealed no significant differences between both methods (t = 1.33, P = 0.193). The Pearson correlation coefficient (0.971, P = 0.0001) indicated a strong linear relationship between the Petrifilm and the standard method. The results showed that Petrifilm is suitable and a convenient alternative to this standard method for the enumeration of aerobic flora in goat soft cheese.

Evaluation of Petrifilm™ method for enumerating aerobic bacteria in Crottin goat's cheese / Evaluación de PetrifilmTM para la enumeración de bacterias aerobias en queso de cabra Crottin

The PetrifilmTM Aerobic Count Plate (ACP) developed by 3M laboratories, is a ready-to-use culture medium system, useful for the enumeration of aerobic bacteria in food. PetrifilmTMwas compared with a standard method in several different food products with satisfactory results. However, many studies showed that bacterial counts in PetrifilmTM were significantly lower than those obtained with conventional methods in fermented food. The purpose of this study was to compare the PetrifilmTM method for enumerating aerobic bacteria with a conventional method (PCA) in Crottin goat's cheese. Thirty samples were used for the colony count. The mean count and standard deviation were 7.18 ± 1.17 log CFU g-1 on PCA and 7.11 ± 1.05 log CFU g-1 on PetrifilmTM. Analysis of variance revealed no significant differences between both methods (t = 1.33, P = 0.193). The Pearson correlation coefficient (0.971, P=0.0001) indicated a strong linear relationship between the PetrifilmTM and the standard method. The results showed that PetrifilmTM is suitable and a convenient alternative to this standard method for the enumeration of aerobic flora in goat soft cheese.

PetrifilmTM Aerobic Count Plate (ACP) desarrollado por 3M es un sistema listo para usar, empleado para el recuento de bacterias aerobias en alimentos. PetrifilmTMfue comparado con los métodos estándar en diferentes productos alimenticios con resultados satisfactorios. Sin embargo, en alimentos fermentados, algunos estudios mostraron que el recuento de bacterias aerobias en PetrifilmTM fue significativamente menor que aquellos obtenidos con los métodos convencionales (PCA). El propósito de este estudio fue comparar el método PetrifilmTM para el recuento de bacterias aerobias con un método convencional en queso de cabra Crottin. Se usaron 30 muestras para el recuento de colonias. Las medias y desviaciones estándar fueron 7,18 ± 1,17 log UFC g-1 en PCA y 7,11 ± 1,05 log UFC g-1 en PetrifilmTM. El análisis de varianza mostró que no había diferencia significativa entre ambos métodos (t = 1,33, P = 0,193). El coeficiente de correlación fue 0,971 ( P = 0,0001) indicando una fuerte correlación lineal. Los resultados muestran a PetrifilmTM como un método apropiado y una alternativa conveniente a los métodos estándar para la cuantificación de flora aeróbica en queso blando de cabra.

Evaluation of Petrifilm method for enumerating aerobic bacteria in Crottin goat cheese.

The Petrifilm Aerobic Count Plate (ACP) developed by 3M laboratories, is a ready-to-use culture medium system, useful for the enumeration of aerobic bacteria in food. Petrifilm was compared with a standard method in several different food products with satisfactory results. However, many studies showed that bacterial counts in Petrifilm were significantly lower than those obtained with conventional methods in fermented food. The purpose of this study was to compare the Petrifilm method for enumerating aerobic bacteria with a conventional method (PCA) in Crottin goats cheese. Thirty samples were used for the colony count. The mean count and standard deviation were 7.18 +/- 1.17 log CFU g(-1) on PCA and 7.11 +/- 1.05 log CFU g(-1) on Petrifilm. Analysis of variance revealed no significant differences between both methods (t = 1.33, P = 0.193). The Pearson correlation coefficient (0.971, P = 0.0001) indicated a strong linear relationship between the Petrifilm and the standard method. The results showed that Petrifilm is suitable and a convenient alternative to this standard method for the enumeration of aerobic flora in goat soft cheese.