The synergistic antioxidant effects of L-proline (Pro), L-methionine (Met), L-lysine (Lys), L-histidine (His) or L-tryptophan (Trp) with a mixed tocopherol concentrate (m-Toc) in cookies were studied by a storage test at 40°C for 12 months after baking. Cookie stability toward oxidative deterioration was evaluated based on changes in peroxide value (POV) of the lipid fraction and the residue amount of added amino acid and tocopherol (Toc).
1) The time course of POV for the control sample without amino acid and/or m-Toc indicated a clear induction period (IP) and IP was prolonged by the addition of any amino acid.
2) Pro most effectively enhanced the antioxidant effect of m-Toc in cookies, followed by Met>Trp>Lys>His.
3) During storage for 12 months, protective effects of amino acid on Toc were noted. When Pro and m-Toc were added together, the residue amount of Toc was higher than with other amino acids, and the residue amount of Pro was highest for any amino acid.
