b-LG > whey model > WPI). Trp residues in a-LA were found to be the amino acid residues most prone to oxidation during heat treatment. In b-LG-containing protein systems, Cys residues were suggested to scavenge most of the reactive oxidants and undergo oxidation-mediated disulfide rearrangement. The rearranged disulfide bonds contributed to protein aggregation (as confirmed by SDS-PAGE analysis), which was suggested to provide further physical protection against oxidation. However, no significant loss of amino acid residues was detected in the heated protein systems after acidic hydrolysis followed by HPLC analysis, which shows only a minor effect of heat treatment on protein oxidation in these pure protein systems.]]>