The β-lactoglobulin content of bovine milk: Development and application of a biosensor immunoassay

An optical biosensor immunoassay exploiting surface plasmon resonance is described for the quantification of β-lactoglobulin in milk. Samples were diluted with buffer, and the protein estimated from binding with a polyclonal antibody immobilised on the sensor surface. Analytical method performance characteristics including range, detection limit, precision and accuracy were determined and reported. The temporal variability in the β-lactoglobulin content of milk from pasture-fed cows during early lactation and across a production season was investigated. The content of β-lactoglobulin decreased from >10 mg mL−1 in early colostrum to <5 mg mL−1 in mature milk, and the β-lactoglobulin content of skim milk powder trended from 25 to 60 mg g−1 across a season. In view of its allergenicity, these data will improve understanding of the expression of innate β-lactoglobulin in the milk of pasture-grazed dairy herds, thereby providing information that is applicable to the formulation of bovine milk-based products.