Development and validation of an enzyme-linked immunosorbent assay for the determination of bovine lactoferrin in various milk products

For the detection of the minor whey protein lactoferrin, a competitive enzyme-linked immunosorbent assay (ELISA) was developed. The method enables the quantification of low lactoferrin concentrations in different matrices. As the good recovery values indicate, the method can be applied for various milk-based products, e.g., milk (104% recovery), cream (106% recovery), curd (96% recovery) and whey (107% recovery). In the validation runs, an accuracy at different concentration levels between 93% and 106% was confirmed, while the precision within a day (91% intra-assay) and between different days (84% inter-assay) was in an acceptable range. The limit of quantification (LOQ) was determined at 62 μg L⁻¹. The applicability was demonstrated by monitoring the lactoferrin content during curd production. An enrichment of lactoferrin in the curd phase (266 mg kg⁻¹) was observed while a large percentage (>39%) of the initial lactoferrin was found in the whey stream.