pH值和EGCG对β-胡萝卜素乳液化学稳定性的影响

Influence of pH and (-)Epigallocatechin-3-gallate on Chemical Stability of β-Carotene Emulsions

摘要:

以β-胡萝卜素为芯材，利用α乳白蛋白（αLA）为乳化剂制备了不同pH值的乳液，并利用表没食子儿茶素没食子酸酯（EGCG）作为抗氧化剂添加到乳液中，考察了不同pH值条件下，EGCG对β-胡萝卜素乳液化学稳定性的影响，探索了EGCG抗氧化机理。结果表明：在pH值2.0和pH值7.0的β胡萝卜素乳液中，EGCG可以作为抗氧化剂抑制β胡萝卜素降解。在pH值2.0的乳液中，未添加EGCG和添加了0.5000%EGCG的乳液在贮藏7d后，β胡萝卜素的保留率分别为50.45%和89.37%；在pH值7.0的乳液中，未添加EGCG与添加了0.1000%EGCG的乳液中，β胡萝卜素的保留率分别为83.97%和9348%，贮藏前后β胡萝卜素乳液的色差发生显著变化（P＜0.05）。

Abstract:

βCarotene is used as a precursor of vitamin A with potent antioxidant activity through singlet oxygen quenching and deactivation of free radicals. Nevertheless, the chemical instability of βcarotene limits its utilization as a nutraceutical ingredients in food industry. Tea polyphenols are often regarded as a highly effective antioxidant for some food applications. Antioxidants such as (-)epigallocatechin3gallate (EGCG) can play dual role in lipid oxidation in oilinwater emulsions in that it can scavenge free radicals but can also reduce transition metals to make them more prooxidative. Therefore, it is important to test the effect of EGCG on βcarotene degradation before it was used in foods. The chemical properties of βcarotene emulsions were characterized, which were stabilized by αlactalbumin (αLA) at different pH values with EGCG as antioxidant. βCarotene concentration and color during storage as well as interfacial EGCG concentration of the emulsions were measured. EGCG can inhibit βcarotene degradation in emulsions at both pH values. After 7 d storage, the percentage of βcarotene remained in the emulsions at pH value of 2.0 without EGCG and with 0.5000% EGCG was 50.45% and 89.37%, respectively. When the maximum concentration of EGCG (0.1000%) was added to the emulsion at pH value of 7.0, 93.48% of the total βcarotene remained after 7 d storage. The color was changed by EGCG addition in emulsions at pH value of 7.0, however, EGCG had no effect on the color of emulsions at pH value of 2.0. The concentration of interfacial EGCG was higher in the emulsions at pH value of 7.0 than that in the emulsions at pH value of 2.0 which can result in higher βcarotene remaining rate in the emulsions at pH value of 7.0.