Elias Ryan J, Bridgewater Juma D, Vachet Richard W, Waraho Thaddao, McClements D Julian, Decker Eric A
Departments of Food Science and Chemistry, University of Massachusetts, Amherst, MA 01003, USA.
J Agric Food Chem. 2006 Dec 13;54(25):9565-72. doi: 10.1021/jf062178w.
The antioxidant activities of aqueous phase beta-lactoglobulin (beta-Lg) and its chymotryptic hydrolysates (CTH) were compared in this study. Proteins and peptides have been shown to inhibit lipid oxidation reactions in oil-in-water emulsions; however, a more fundamental understanding of the antioxidant activity of these compounds in dispersed food lipid systems is lacking. CTH was more effective than an equivalent concentration of beta-Lg in retarding lipid oxidation reactions when dispersed in the continuous phase of Brij-stabilized oil-in-water emulsions (pH 7). Furthermore, it was observed that CTH had higher peroxyl radical scavenging and iron-binding values than beta-Lg. Liquid chromatography-mass spectrometry (LC-MS) was used to measure the rate of oxidation of three oxidatively labile amino acid residues (Tyr, Met, and Phe) in certain CTH peptide fragments. Significant oxidation of specific Tyr and Met residues present in two separate 12 amino acid peptide fragments was observed in the days preceding lipid oxidation (39 and 55% of Tyr and Met were oxidized, respectively, by day 4 of the study); however, no significant oxidation of the Phe residue present in a specific 14 amino acid peptide fragment could be observed during the same time period. These data could suggest that Met and Tyr residues are capable of scavenging radical species and have the potential to improve the oxidative stability dispersed food lipids.
本研究比较了水相β-乳球蛋白（β-Lg）及其胰凝乳蛋白酶水解产物（CTH）的抗氧化活性。蛋白质和肽已被证明可抑制水包油乳液中的脂质氧化反应；然而，对于这些化合物在分散的食品脂质体系中的抗氧化活性，仍缺乏更深入的了解。当分散在Brij稳定的水包油乳液（pH 7）的连续相中时，CTH在延缓脂质氧化反应方面比同等浓度的β-Lg更有效。此外，观察到CTH的过氧自由基清除能力和铁结合值高于β-Lg。采用液相色谱-质谱联用（LC-MS）测定了某些CTH肽片段中三个氧化不稳定氨基酸残基（酪氨酸、蛋氨酸和苯丙氨酸）的氧化速率。在脂质氧化前的几天内，观察到两个单独的12个氨基酸肽片段中存在的特定酪氨酸和蛋氨酸残基发生了显著氧化（在研究的第4天，分别有39%和55%的酪氨酸和蛋氨酸被氧化）；然而，在同一时间段内，未观察到特定14个氨基酸肽片段中存在的苯丙氨酸残基有显著氧化。这些数据表明，蛋氨酸和酪氨酸残基能够清除自由基，并有潜力提高分散食品脂质的氧化稳定性。
