Impact of milk components in recovery of the MS2 bacteriophage as an indicator of enteric viruses

The objective of this study was to characterize the role of milk components in the recovery of viral particles from raw milk. For such characterization, four model milk formulations (A-D) were constituted by mixing different combinations of lactose, whey protein, casein, and fat into water. Each model formulation was spiked with six concentrations of bacteriophage MS2. The soluble and insoluble components of each model milk formulation were separated by centrifugation at 40,000×g and viruses were enumerated in each supernatant fluid and pellet by the double agar layer (DAL) method. When samples were spiked with MS2 at concentrations lower than 4.8×10⁵pfu/ml, milk components did not significantly impact the overall recovery. However, the impact of milk components was measurable at higher concentrations. In general, higher numbers of MS2 were recovered from supernatant fluids of model milk formulations containing no fat. The highest number of viral particles were recovered from the pellet of model C (lactose+whey protein+casein). The recovery efficiency of MS2 was correlated with the dry matter contents of each model milk formulation and the initial spiking concentration of coliphage using response surface modeling.