Response surface methodology applied to the generation of casein hydrolysates with antioxidant and dipeptidyl peptidase IV inhibitory properties

BACKGROUND Hydrolysis parameters affecting the release of dipeptidyl peptidase IV ( DPP‐IV ) inhibitory and antioxidant peptides from milk proteins have not been extensively studied. Therefore, a multifactorial (i.e. pH , temperature and hydrolysis time) composite design was used to optimise the release of bioactive peptides ( BAPs ) with DPP‐IV inhibitory and antioxidant [oxygen radical absorbance capacity ( ORAC )] properties from sodium caseinate. RESULTS Fifteen sodium caseinate hydrolysates ( H1–H15 ) were generated with Protamex TM , a bacillus proteinase activity. Hydrolysis time (1 to 5 h) had the highest influence on both DPP‐IV inhibitory properties and ORAC activity ( P < 0.05). Alteration of incubation temperature (40 to 60 °C) and pH (6.5 to 8.0) had an effect on the DPP‐IV inhibitory properties but not the ORAC activity of the Protamex sodium caseinate hydrolysates. A multi‐functional hydrolysate, H12 , was identified having DPP‐IV inhibitory (actual: 0.82 ± 0.24 vs. predicted optimum: 0.68 mg mL −1 ) and ORAC (actual: 639 ± 66 vs. predicted optimum: 639 µmol TE g −1 ) activity of the same order ( P > 0.05) as the response surface methodology ( RSM ) predicted optimum bioactivities. CONCLUSION Generation of milk protein hydrolysates through multifactorial design approaches may aid in the optimal enzymatic release of BAPs with serum glucose lowering and antioxidant properties. © 2016 Society of Chemical Industry