Partition of Lactococcus lactis bacteriophage during the concentration of micellar casein by tangential 0.1 μm pore size microfiltration

Retention behaviour of two lactococcal phages added to raw milk submitted to cross flow microfiltration with a 0.1 urn pore size membrane was studied. The microfiltrate, 'rnilk without casein', contains 0.4-0.14% of the phage particles added to the milk whatever the phage type and the level of inoculation. Such a retention cannot be explained by electrostatic interactions between phage particle and casein micelle or microfiltration membrane but is more probably due to a reduction of membrane pore size resulting from a concentration polarlzation phenomenon.