Cronobacter Support
05-22-2009, 07:47 PM
1st International Conference on Cronobacter Poster Abstract 47
Effect of Different Factors on Enterobacter sakazakii Heat and PEF Resistance
Due to the physiological characteristics of Enterobacter sakazakii and the current tendency to produce minimally processed foods it is foreseeable an increase in the sanitary importance of this species. A deeper knowledge of the environmental factors affecting the efficacy of currently available food preservation technologies, i.e. heat treatments, and alternative processes, such as Pulsed Electric Fields (PEF), is required in order to improve their lethal effect. However, present knowledge about the influence of these factors on E. sakazakii heat resistance is limited and there is almost no data available about their effect on its PEF resistance. The aim of this work was to study the influence of time (up to 120 h) and temperature (10, 20, 30 and 37 ºC) of growth, and pH (4.0, 5.0, 6.0 and 7.0) and water activity (0.27, 0.54, 0.81 and 1.08 g sucrose/ml) of the treatment medium on E. sakazakii heat and PEF resistance. E. sakazakii CECT 858 (ATCC 29544) was grown to stationary phase, and its resistance to both technologies was measured by the multipoint method. A mixing method (thermorresistometer TR-SC) was used for the determination of microbial heat resistance, and exponential waveform pulse equipment was used for PEF-resistance determinations. Entering into stationary growth phase triggered an increase in resistance against both technologies. Longer incubation times (up to 120 h) resulted in a gradual increase of resistance to heat but not to PEF. Decimal reduction time values increased exponentially with growth temperature up to 37 ºC, however PEF resistance was not influenced by this factor. E. sakazakii showed maximum heat resistance at pH close to neutrality (pH 6.0). On the contrary, PEF resistance was higher at the lower pH (pH 4.0). A decrease in the water activity of the treatment medium had the same protective effect on both technologies and resulted in cells that were nine times more heat resistant and eleven times more PEF resistant. Our results demonstrate the importance of the studied factors on E. sakazakii heat and PEF resistance, which should be taken into account when designing heat and PEF based hygienization processes.
Cristina Arroyo, Rafael Pagán and Santiago Condón
Unidad de Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza C/ Miguel Servet, nº 177, 50013, Zaragoza, Spain.
Effect of Different Factors on Enterobacter sakazakii Heat and PEF Resistance
Due to the physiological characteristics of Enterobacter sakazakii and the current tendency to produce minimally processed foods it is foreseeable an increase in the sanitary importance of this species. A deeper knowledge of the environmental factors affecting the efficacy of currently available food preservation technologies, i.e. heat treatments, and alternative processes, such as Pulsed Electric Fields (PEF), is required in order to improve their lethal effect. However, present knowledge about the influence of these factors on E. sakazakii heat resistance is limited and there is almost no data available about their effect on its PEF resistance. The aim of this work was to study the influence of time (up to 120 h) and temperature (10, 20, 30 and 37 ºC) of growth, and pH (4.0, 5.0, 6.0 and 7.0) and water activity (0.27, 0.54, 0.81 and 1.08 g sucrose/ml) of the treatment medium on E. sakazakii heat and PEF resistance. E. sakazakii CECT 858 (ATCC 29544) was grown to stationary phase, and its resistance to both technologies was measured by the multipoint method. A mixing method (thermorresistometer TR-SC) was used for the determination of microbial heat resistance, and exponential waveform pulse equipment was used for PEF-resistance determinations. Entering into stationary growth phase triggered an increase in resistance against both technologies. Longer incubation times (up to 120 h) resulted in a gradual increase of resistance to heat but not to PEF. Decimal reduction time values increased exponentially with growth temperature up to 37 ºC, however PEF resistance was not influenced by this factor. E. sakazakii showed maximum heat resistance at pH close to neutrality (pH 6.0). On the contrary, PEF resistance was higher at the lower pH (pH 4.0). A decrease in the water activity of the treatment medium had the same protective effect on both technologies and resulted in cells that were nine times more heat resistant and eleven times more PEF resistant. Our results demonstrate the importance of the studied factors on E. sakazakii heat and PEF resistance, which should be taken into account when designing heat and PEF based hygienization processes.
Cristina Arroyo, Rafael Pagán and Santiago Condón
Unidad de Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza C/ Miguel Servet, nº 177, 50013, Zaragoza, Spain.