Influence of milk ultrafiltration on bacteriophages of lactic acid bacteria.

Bacteriophages added to whole milk were partially concentrated during ultrafiltration. At 4:1 retentate, phage had concentrated 2.4:1. Thermal destruction at 54 degrees C followed first order kinetics up to 6% protein, whereafter it deviated. When allowed to grow in retentate in the presence of appropriate host, 3.5 generations of phage appeared after 12 h at 22 degrees C compared with four generations in skim milk. In the presence of phage, lactic acid bacteria population increased to only 10(7) cfu/ml compared with 3 X 10(9) in their absence. Retentate starter prepared in the presence of phage was as active as skim milk starter prepared in the presence of phage.