Immunochromatographic lateral-flow test strip for the rapid detection of added bovine rennet whey in milk and milk powder

An immunochromatographic lateral-flow test dipstick test was developed for the fast detection of bovine rennet whey in liquid milk and milk powder. The test is based on the binding of casein glycomacropeptide (cGMP) by two specific anti-bovine κ-casein monoclonal antibodies and has a visual detection limit of around 15 ng mL^?1 for cGMP and 1% (v/v) for rennet whey in milk using standards and spiked samples. The dipstick performance was evaluated in a collaborative trial using skim milk powder and raw, pasteurized and UHT milk. The suitability of the dipstick was demonstrated in comparison with gel permeation-high performance liquid chromotography and a colorimetric method, by analysing 60 raw milk samples collected from farms in Brazil. The dipstick results correlated well with the HPLC results and were more reliable than those obtained with the colorimetric method. The dipstick test correctly identified all raw milk samples with a rennet whey content above 4%.