Identification of antioxidant peptides in cheddar cheese made with adjunct culture Lactobacillus casei ssp. casei 300

Abstract

Cheddar cheese was prepared from cow milk with adjunct culture Lactobacillus casei ssp. casei 300 and antioxidant peptides (< 3kDa) were fractionated and purified on C 18 RP-HPLC column chromatography. The antioxidant activity of each RP-HPLC fraction was determined by ABTS (2,2'-azinobis-3-ethyl-benzothiazoline-6-sulphonic acid) radical assay method and expressed in terms of Trolox equivalent antioxidant capacity (TEAC) values (i.e. μmol of Trolox equivalence/ mg of the protein). The fraction exhibiting the highest antioxidant activity was rechromatographed on RP-HPLC to obtain a single peak, which was subjected to LC-MS/MS. Two milk protein derived peptides have been identified: VKEAMAPK (m/z 872.5048) matching f (98-105) of β-casein and HIQKEDVPSER (m/z 1336.7034) corresponding to α s1 -casein f (80-90). Synthetic peptides were prepared using these sequences. The DPPH (2, 2-Diphenyl-1-picrylhydrazyl) radical scavenging activity of synthetic peptide VKEAMAPK was comparable to commercial chemical antioxidants (BHA, t-BHQ, Ferulic acid), while it was slightly lower for synthetic peptide HIQKEDVPSER.