Quantification of dabsylated di- and tri-peptides in fermented milk

An improved HPLC method using pre-column dabsyl chloride derivatisation for the separation and quantification of antihypertensive di- and tri-peptides in fermented milk products was established. The dabsylated peptides Val-Pro-Pro (VPP), Ile-Pro-Pro (IPP), Leu-Pro-Pro (LPP) and Phe-Pro (FP) were separated on a C18-column coupled to UV/VIS and mass spectrometric detector, respectively. Due to the derivatisation of the peptides, an HPLC base line separation was achieved and the peak width was improved. The VIS-spectrometry did not allow a good quantification of these peptides since more than one peptide co-eluted under one single peak. In contrast applying LC–ESI–MS with a single quadrupole much better quantification of the dabsylated peptides was done. In Evolus® (Valio Ltd., Finland), a fermented milk drink, 6.9 mg L−1 for VPP, 6.1 mg L−1 for IPP, 0.8 mg L−1 for LPP and 3.2 mg L−1 for FP were determined. In fermented reconstituted milk (Lactobacillus helveticus, 37 °C, 48 h) lower concentrations of these peptides were determined (0.7, 0.6, 0.0 and 2.2 mg L−1, respectively).