Effect Of EGCG On β-carotene Degradation And The Stability Of β-carotene In Oil-in-water Emulsion Stabilized By α- Lactalbumin

β-Carotene is used in food industry as a precursor of vitamin A with potent antioxidant activity through singlet oxygen quenching and deactivation of free radicals. Nevertheless, their utilization as nutraceutical ingredients in food industry is currently limited because of their poor water-solubility, high melting point, chemical instability and low bioavailability. Emulsion-based systems are often a better choice for delivering bioactive lipids such as β-carotene into functional foods since the emulsion increase bioavailability. Tea polyphenols are often regarded as a highly effective antioxidant for some food applications. Antioxidants such as 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. In addition, EGCG can interact with milk protein and the complex may have effects on the physical and chemical stability of emulsion. Therefore, it was important to test the effect of EGCG on P-carotene degradation and the stability of emulsion before it is used in foods. In this research, we investigate the effect of a-LA and EGCG on the physical and chemical stability of β-carotene emulsion and the mechanism of both two to inhibit β-carotene degradation and fatty acid oxidation. The results are following:(1) The amount of a-LA as emulsifier has significant effects on the physical and chemical stability of β-carotene emulsion. It can be a good emulsifier and the proper amount of addition is 1.5% in β-carotene in oil-in-water emulsion.(2) EGCG addition had no effect on particle size, zeta-potential and the encapsulation rate of emulsion. However, the addition of EGCG significantly influenced the physical stability of the emulsions. When the addition of EGCG was higher than 0.2% in the emulsion at pH 2.0, the physical stability decreased with the increasing addition. The stability of emulsion at pH 7.0 was improved by the addition of EGCG in 0.0025-0.02%; however, the stability of the emulsion decreased with 0.02%-0.1% EGCG addition. After adding EGCG higher than 0.1%, the emulsion separated into two phase quickly due to the interaction of EGCG and a-LA.(3) EGCG can inhibit β-carotene degradation in emulsion at pH 2.0 and pH 7.0. The color was changed by EGCG addition in emulsions at pH 7.0. However, EGCG had no effect on the color of emulsions at pH 2.0.(4) EGCG was more important than a-LA in stabilizing β-carotene in the a-LA-stabilized oil-in-water emulsions but that at high EGCG and a-LA concentrations, there could be additional protection from the combination. The inability of a-LA to protect β-carotene could be because metals were not the major prooxidants in the emulsion.(5) β-carotene increased lipid oxidation in β-carotene in corn oil-in-water emulsions. EGCG was effective at protecting β-carotene, but it had no effect on fatty acid oxidation in β-carotene in corn oil-in-water emulsion.EGCG is an effective antioxidant in β-carotene in both MCT- and corn oil-in-water emulsions. When EGCG is used in β-carotene emulsion, it is important to pay attention to the amount of addition and the pH of emulsion.