Survival of Salmonella spp. in minced meat packaged under vacuum and modified atmosphere

Abstract The effect of different modified atmosphere packaging regimes on the behavior of Salmonella spp. on minced meat was studied. Minced meat was experimentally contaminated with a Salmonella spp. cocktail (S. Enteritidis, S. Typhimurium, S. Infantis and S. Arizonae), packaged under vacuum or modified atmosphere with initial headspaces containing 20%O2/50%CO2/30%N2 and 20%O2/30%CO2/50%N2) and stored at 3 ± 1 °C for 12 days. Samples were analyzed for Salmonella spp., viable and lactic acid bacteria count every third day. Salmonella spp. counts decreased during storage in all packaging types, with reductions of about 1.5 log CFU/g. A significant difference (p < 0.01) was noted between Salmonella spp. counts in meat packaged in vacuum and modified atmospheres, although there was no significant difference in Salmonella spp. count between meat packaged in 50%CO2, and meat packaged in 30%CO2. At the end of the study, there were significant differences (p < 0.01; p < 0.05) in total viable and lactic acid bacterial counts between meat packaged in vacuum and modified atmosphere, and the lowest counts were noted in meat packaged in modified atmosphere with 50%CO2.

Effect of high hydrostatic pressure on the barrier properties of polyamide-6 films

Little is known about the barrier properties of polymer films during high pressure processing of prepackaged foods. In order to learn more about this, we examined the influence of high hydrostatic pressure on the permeation of raspberry ketone (dissolved in ethanol/water) through polyamide-6 films at temperatures between 20 and 60°C. Permeation was lowered by increasing pressure at all temperatures. At 23°C, the increasing pressure sequence 0.1, 50, 100, 150, and 200 MPa correlated with the decreasing permeation coefficients P/(10(9) cm² s-1) of 6.2, 3.8, 3.0, 2.2, and 1.6. Analysis of the permeation kinetics indicated that this effect was due to a reduced diffusion coefficient. Pressure and temperature acted antagonistically to each other. The decrease in permeation at 200 MPa was compensated for by a temperature increase of 20°C. After release of pressure, the former permeation coefficients were recovered, which suggests that this `pressure effect' is reversible. Taken together, our data revealed no detrimental effects of high hydrostatic pressure on the barrier properties of polymer films.

Detección de Listeria monocytogenes en distintos productos alimenticios y en muestras ambientales de una amplia cadena de supermercados de la ciudad de Bahía Blanca (Argentina) / Listeria monocytogenes detection in different food products and environmental samples of supermarkets of Bahía Blanca city (Argentine)

En el período comprendido entre enero de 2002 y julio de 2003 se realizó este trabajo que consistió en la detección de Listeria monocytogenes en diferentes alimentos: 90 muestras de fiambres cocidos, fraccionados y envasados con diferentes metodologías y 132 muestras de queso de pasta blanda. Estos productos fueron analizados utilizando el criterio presencia-ausencia en 25 g de alimento. L. monocytogenes no se halló ni en los fiambres feteados en las ventas personalizadas ni en las muestras de queso analizadas. Por el contrario, se determinó su presencia en el 10% de los fiambres feteados envasados al vacío y en el 5% de los fiambres trozados envasados al vacío. Estos resultados nos llevaron a incluir la investigación de la presencia de este patógeno en diferentes muestras medioambientales. Para ello se hisoparon 115 puntos incluyendo las líneas de procesamiento, materias primas, utensilios, heladeras. L. monocytogenes se halló en el 13,2% de las muestras analizadas: 5% correspondieron a la sala de fraccionamiento de fiambres y lácteos, 6,7% al frigorífico y 1,5% a los sitios de venta personalizada. Estos resultados indicaron la posible existencia de sitios problemáticos donde el microorganismo tendría probabilidad de formar reservorios, por lo que se extremaron las medidas rutinarias de higiene y desinfección.

This work on Listeria monocytogenes detection in different foods was carried out between January 2002 and July 2003. Ninety cold-served cooked meats, sliced and packaged by different methods and 132 pieces of soft cheeses were studied. These products were analyzed using the presence/ausence in 25 g criterion. L. monocytogenes was not found either in foods sliced over the counter or in controlled cheeses, but it was found in 10% of sliced cold-served foods and 5% of cut and cold-served meats vacuum packaged. These results led us to investigate the presence of these pathogen bacteria in different environmental samples. A hundred and fifteen points were swabbed including processing lines, raw materials, tools, and refrigerators. L. monocytogenes was found in 13.2% of the analyzed samples: 5% in packaging sector, 6.7% in meat processing lines and 1.5% in personalized sales. These results showed the presence of sites wherethe microorganismmay reside and create reservoirs, so that routinary measures of hygiene and disinfection were increased.