Release of dipeptidyl peptidase IV (DPP-IV) inhibitory peptides from milk protein isolate (MPI) during enzymatic hydrolysis.The release of dipeptidyl peptidase IV (DPP-IV) inhibitory peptides from bovine milk protein isolate (MPI) during trypsin hydrolysis was studied using a design of experiments (DOE) approach.  A 3 factor×3 level DOE including temperature (40, 50 and 60°C), enzyme to substrate ratio (E:S; 0.50, 1.25 and 2.00% (w/w)) and hydrolysis time (60, 150 and 240min) was used during the generation of 15 hydrolysates (H1-H15). 
DOE
The DPP-IV IC50 value of 0.69mgmL-1, predicted by response surface methodology (RSM), to be obtained with an hydrolysate generated at 50.5°C, 2% ES and 231min (H16) was similar to the experimentally obtained value (DPP-IV IC50=0.66±0.10mgmL-1, p>0.05, n=3). 
RSM
Potent known DPP-IV inhibitory peptide sequences were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) within H16, some of which were also present within H16_CorPP. 
LC-MS/MS