An immunoassay to assess lamb and kid rennets authenticity

The potential adulteration of kid or lamb rennet with calf rennet is of interest for some Protected Designation of Origin cheeses producers and those looking for a specific cheese typicality. The approach proposed here for the authentication of kid or lamb rennet is based on the immuno-detection of bovine pepsin possibly present in calf rennet in varying quantities. The developed immunoassay (indirect ELISA) used a monoclonal antibody (mAb) raised against bovine pepsin. This mAb was found to be specific as it didn't cross-react with the pepsin of animal species other than bovine (kid, lamb, pig) and with other milk-clotting enzymes (chymosin and microbial enzymes). Adulteration tests were conducted with kid and lamb rennets spiked with a wide range of calf rennet (from 0 to 100% v/v). The presence of bovine pepsin was detected at low levels down to 6 mg/L in kid and lamb rennets. Good linear relationships were obtained between added bovine pepsin concentration and the absorbance values over the range 1.25-120 mg/L. Results showed that indirect ELISA proved to be an interesting tool for testing rennets authenticity targeting bovine pepsin as an indicator of the bovine adulteration of kid and lamb rennets.