Quantification of Immunoglobulin G in Bovine and Caprine Milk Using a Surface Plasmon Resonance-Based Immunosensor

Detection of colostrum in bovine and caprine milks is essential for dairy industries to avoid negative economical and technological consequences. One of the best markers of the presence of colostrum is immunoglobulin G (IgG). Two quantification methods have been evaluated for IgG in bovine or caprine milk, based on the real-time immunodetection of IgG by surface plasmon resonance (SPR) spectroscopy. Calibration curves were established by extracting affinity data from the sensorgrams, either using the residual bound IgG level after the association and dissociation phases or using the IgG binding rate during the association phase. The binding rate method allows for substantially reduced analysis times of below 4 min, which make it compatible with the milking time of small ruminants. Moreover, the binding rate method showed a better analytical performance, with lower detection limit and higher precision and accuracy than the residual binding method.