中文摘要：

共轭亚油酸（conjugated linoleic acid,CLA）是一种具有多重生理功效的不饱和脂肪酸,其氧化稳定性较差,对光、热、氧气很不稳定。以亲水胶体为乳化剂制备CLA的水包油（O/W）型乳液可改善其氧化稳定性,扩大其在食品中的应用。该研究采用改性阿拉伯胶EM2为乳化剂、2种不同黏度的CLA为油相,通过测定乳液颗粒的粒径和粒径分布以及乳液在40℃贮存过程中的过氧化值和茴香胺值,研究了CLA的水包油（O/W）型乳液的物理化学稳定性。结果表明,高质量分数的EM2有利于形成粒径更小且分布均一的乳液颗粒。乳液的氧化稳定性很大程度上依赖于其物理稳定性。对于黏度较小的CLA,在各测试EM2质量分数下,CLA乳液具有较好的物理稳定性,且随着EM2质量分数的增大,乳液氧化稳定性提高。对于黏度较大的CLA,EM2质量分数为5%时,乳液具有较好的物理化学稳定性;增大EM2的质量分数,其稳定性下降。该研究可为今后研究基于乳液技术的功能性因子保护和增效提供参考,有利于CLA在食品行业中的推广应用。

英文摘要：

Conjugated linoleic acid （CLA） is one of the unsaturated fatty acids that have multiple bioactivities. It is liable to oxidation, particularly when exposed to light, heat and oxygen. Encapsulation of CLA in O/W emulsions stabilized by hydrocolloids could improve the oxidative stability of CLA, and could extend its applications in foods. This paper investigated the physical and chemical stabilities of O/W emulsions prepared with two CLAs of different viscosities and stabilized with modified gum arabic EM2. The O/W emulsions consisted of 15% CLA and 5%-25% EM2, and were prepared by pre-homogenization using a high-speed blender followed by one pass through a high-pressure homogenizer at 75 Mpa. The physical stability of CLA emulsions was evaluated by measuring the change of particle size and size distribution during storage at room temperature （25℃） and at an elevated temperature （60℃）, whilst the chemical stability was characterized by the formation of lipid oxidation products. The concentration of primary lipid oxidation products was measured using the peroxide value （PV） method and the concentration of secondary oxidation products measured using the anisidine value （AV） assay. The results show that higher EM2 concentrations lead to finer and more homogenous emulsions. CLA oxidative stability is dependent on the physical stability of emulsions. For the CLA with lower viscosity, at all EM2 concentrations investigated, the emulsions show good physical stability with no significant changes in particle size distribution within seven days both at 25℃ and 60℃. The oxidative stability correlates positively with EM2 concentration. For the other CLA with higher viscosity, excessive concentration of EM2 could reduce physical stability and thus decrease oxidative stability of CLA emulsions. 5% EM2 was found to be the optimal concentration stabilizing CLA emulsions. The reduced physical stability of CLA emulsions at higher EM2 concentrations could be due to the depletion force effect caused by the