Enzyme-linked immunosorbent assay for the detection of bovine rennet whey powder in milk powder and buttermilk powder

An inhibition enzyme-linked immunosorbent assay (ELISA) for the detection of bovine rennet whey (BRW) solids in skim milk powders (SMP) and buttermilk powders is presented. The BRW content was determined in a neutralised trichloroacetic acid sample extract by binding of the dissolved caseinomacropeptide to an enzyme-labelled anti-bovine-κ-casein monoclonal antibody. Calibration curves were constructed by analysing SMP standards with different known concentrations of BRW (0–5.8% (w/w)).The assay has a limit of detection of 0.1% (w/w) BRW powder in SMP and has high repeatability and reliability. The ELISA reached the sensitivity required for screening to conform with European Union (EU) legislation. It is easy to use, has a short assay time and is of low cost. The successful applicability of this new screening assay was demonstrated in comparison with chromatographic methods imposed by the EU, where 60 industrial samples taken by the Dutch General Inspection Service were analysed.