An optical biosensor-based immunoassay for the determination of bovine serum albumin in milk and milk products

An automated biosensor immunoassay, exploiting surface plasmon resonance detection, is described for the quantitation of bovine serum albumin (BSA) in milk products. Antibody selection, assay conditions and potential non-specific binding interferences were defined. Analytical performance includes a working range of 10–1000 ng mL−1, a method detection limit of 0.02 mg g−1 in milk, an instrument intermediate precision relative standard deviation (RSDiR) of 3.7%, an intermediate precision RSDiR of 8.9% for whey protein concentrate, and a single flow cell stable for at least 400 cycles. Accuracy was demonstrated by recovery, compliance with a certified reference material and comparison with a high performance liquid chromatographic method. The technique was applied to the estimation of BSA content of bovine milk, colostrum, whey protein fractions and infant formulae. The change in BSA expression during early bovine lactation and across a production season, and the thermal denaturation of BSA were also investigated.