Goat milk proteins have gained increasing attention especially the bioactive peptides released from the parent
proteins by digestive enzymes. Specifically, the interest in bioactives of goatmilk is intensifying due to its reduced
allergenicity compared to bovine milk. In this study, proteins of goat milk were fractionated into caseins (GCP)
andwhey proteins (GWP), hydrolyzed by pepsin and the generated peptides were examined for radical scavenging
activities. The hydrolysates ofwhey (P-GWP) and casein (P-GCP) proteins exhibited potent superoxide anion
(O2 ・−) scavenging activity in a dose-dependent manner, as investigated using the natural xanthine/xanthine
oxidase (X/XOD) system. The P-GWP and P-GCP dramatically quenched the O2 ・− flux but had negligible effect
on the catalytic function of the enzyme, indicating specificity to scavenge O2 ・− but not oxidase inhibition. Further,
both P-GWP and P-GCPwere able to remarkably quench the chemical DPPHradical. Fractionation of hydrolysates
by size-exclusion chromatography produced four fractions (F1-F4) from both hydrolysates, with variable O2 ・−
scavenging activities. However, the slow eluting fractions (F4) of both hydrolysates and fast eluting fraction
(F2) of P-GCP contained peptides with the highest scavenging activities. Peptides in the active fractions of
P-GWP and P-GCP, isolated by reversed phase-HPLC, exhibited significantly strong O2 ・− scavenging activities.
MALDI-TOF-MS allowed the identification of several antioxidant peptides derived from both caseins and whey
proteins, with β-casein and β-lactoglobulin being the major contributors, respectively. The results demonstrate
that digestion with pepsin generates multiple soluble peptides fromgoatmilk protein fractions with remarkable
ability to scavenge superoxide radicals and thus providing a fascinating opportunity for their potential candidacy
as antioxidant bioactive peptides.