Quantification of bio- and techno-functional peptides in tryptic bovine micellar casein and β-casein hydrolysates

Numerous peptides generated by triptic hydrolysis of micellar casein and β-casein from bovine milk have been reported to exhibit bio-functional or techno-functional activities. In this study, the focus was placed on the quantification of eleven potential functional peptides generated by enzymatic hydrolysis with trypsin. The identity of the target peptides was verified by LC-ESI-MS/MS and a reverse phase high performance liquid chromatography method (RP-HPLC) was established to quantify the peptides. The quantification was based on calibration curves drawn using synthesised purified peptides. The regression analysis comparing >30 standard measurements of each peptide standard showed a regression coefficient R(2)>0.9958. The inter-day repeatability of the quantification method was always within a relative error of 0.2-6.5%, while the relative error of the accuracy for reproducibility was in the range of 0.1-2.4%. The established method was successfully applied for the quantitative analysis of the eleven functional peptides in different dairy fractions generated by cross-flow ultrafiltration.