Retention of Listeria and Salmonella cells contaminating skim milk by tangential membrane microfiltration ("Bactocatch" process)

Retention by tangential membrane ultrafiltration of non-virulent Listeria and Salmonella cells whose morphological and physiological characteristics were close to pathogenic strains was studied.The bacteria were added to raw milk, pasteurized milk or previously microfiltered milk.Decimal reductions observed at 35°C were close to 1.9 units for Listeria and 2.5 units for Salmonella.The reduction was not influenced by contamination level (between 10 2 and 10 6 CFU/ml).An increase of microfiltration temperature resulted in a significant increase of Salmonella retention (only 0.05% of the bacteria added was found in the micro-filtered milk) but had no effect on Listeria retention.The possible obtention of cheeses made from raw milk with a satisfactory Ievel of hygiene is discussed.milk 1 microfiltration / Salmonella / Listeria Résumé -Rétention de Listeria et Salmonella par le procédé de microfiltration tangentielle