中文摘要：

研究了乳状液体系中不饱和脂肪酸的氧化机制，重点探讨了乳化剂种类、用量、pH和EDTA对大豆油乳化体系（O／W）氧化稳定性的影响。结果显示：乳化剂种类和pH对于乳状液体系的氧化稳定性有显著影响，对于阴离子乳化剂SDS稳定的乳状液，pH4．0的氧化速率比pH7．0和9．0快得多；对于非离子乳化剂Tween20稳定的乳状液，pH的影响不显著；对于阳离子乳化剂CTAB稳定的乳状液，随着pH的升高，氧化速率变快；同时在pH4．0条件下，氧化速率SDS〉CTAB〉Tween20，而在pH7．0和9．0条件下，氧化速率CTAB〉SDS≌Tween20。乳状液体系中自带的微量金属离子对于体系也有相当大的影响，随着金属离子螯合剂EDTA浓度的增加，其乳状液氧化速率显著降低。乳化剂用量也会影响体系的氧化稳定性，随着乳化剂用量的增加，乳状液的氧化稳定性变差，这种稳定性的弱化是由于粒径变小、油滴表面积增大引起的。

英文摘要：

The effect of emulsifier type, pH, EDTA and particle size on the oxidation of soybean oil in O/W emulsions was studied in this paper. O/W emulsions were prepared with 25% （V ： V） soybean oil, 0.5-1.0 mM EDTA, and 1% （ V ： V ） anionic （ SDS ; DBS） , cationic （ CTAB ; CPBM）, or nonionic （sorbitan monolaurate, Span20; polyoxyethylene sorbitan monolaurate, Tween 20; sugar ester, SE-15） emulsifiers in 25 mM citrate-phosphate （ pH 4.0） or 25 mM phosphate （ pH 7.0 and 9.0） buffer. The emulsions were stored at 37 （C and auto-oxidation was monitored by measuring peroxide value （POV）. Emulsions stabilized by SDS had the highest lipid oxidation rate compared with those stabilized by cationic and nonionic emulsifiers at pH 4.0, while CTAB-stabilized emulsions oxidized the most rapidly under pH 7.0 and 9.0. The addition of EDTA to Tween 20-stabilized emulsions greatly suppressed （ P 〈 0.05 ） the lipid oxidation. Droplet size distribution was influenced by emulsifier content and showed with the decreasing of diameter the oxidation of the O/W emulsions incereased. The results indicated that oxidative stability of soybean oil in O/W emulsions was critically affected by the emulsifier types and the . An optimum oxidative stability can be achieved through controlling the pH of the continuous phase of the emulsion and the addition of proper metal ion chelators.