Sato-Ishizaki Yumi, Iguchi Atsuhiro, Someya Keita, Kusumoto Ibuki, Kato Shunji, Nakagawa Kiyotaka, Gotoh Naohiro
Functional Foods Division, Yokohama Oils and Fats Industry Co., Ltd.
Laboratory of Food Function Analysis, Graduate School of Agricultural Science, Tohoku University.
J Oleo Sci. 2025;74(8):729-737. doi: 10.5650/jos.ess25092.
The oxidative stability of polyunsaturated fatty acid (PUFA) generally decreases with increasing unsaturation, however, the opposite results have been reported for aqueous emulsions prepared from PUFA. One study showed that among PUFA (fish oil) emulsions with varying μm-sized particles, the smaller emulsions had better oxidation stability. Thus, particle size may be involved in the mechanism behind the improved oxidative stability of PUFA by emulsification, and PUFA emulsions with even smaller particle sizes (i.e., nm-sized) may exhibit higher stability. To evaluate these hypotheses, once optimizing conditions under which emulsions with different sizes (100-250 nm) can be prepared using docosahexaenoic acid (DHA)-rich algal oil (DAO), these emulsions were subjected to thermal oxidation (40°C, 5 days under light shielding). Based on peroxide value (POV) data, it is apparent that even DHA, which is particularly prone to oxidation, becomes less susceptible to thermal oxidation when emulsified, and that smaller emulsions lead to greater oxidative stability. The high oxidation stability in the smallest emulsion remained high after removal of the antioxidants (tocopherols) from this emulsion. Considering these results together with preliminary data on triacylglycerol (TG) mono-hydroperoxides measured by high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS), the physical properties of the emulsion might account for the greater oxidative stability in smaller emulsions, probably due to the rapid termination of the oxidation reaction within the smaller particle in a more substrate-dense environment, rather than to the action of antioxidant tocopherols. Further research will hopefully lead to a solution to the longstanding problem of oxidation of PUFA such as DHA, which has a variety of benefits.
多不饱和脂肪酸（PUFA）的氧化稳定性通常会随着不饱和度的增加而降低，然而，有关由PUFA制备的水包油乳剂却报道了相反的结果。一项研究表明，在具有不同微米尺寸颗粒的PUFA（鱼油）乳剂中，较小的乳剂具有更好的氧化稳定性。因此，粒径可能参与了通过乳化提高PUFA氧化稳定性的机制，并且具有更小粒径（即纳米尺寸）的PUFA乳剂可能表现出更高的稳定性。为了评估这些假设，一旦优化了使用富含二十二碳六烯酸（DHA）的藻油（DAO）制备不同尺寸（100 - 250纳米）乳剂的条件，就将这些乳剂进行热氧化（40°C，避光5天）。基于过氧化值（POV）数据，很明显，即使是特别容易氧化的DHA，在乳化后也变得较不易受热氧化影响，并且较小的乳剂导致更高的氧化稳定性。从该乳剂中去除抗氧化剂（生育酚）后，最小乳剂中的高氧化稳定性仍然很高。将这些结果与通过高效液相色谱 - 串联质谱（LC - MS/MS）测量的三酰甘油（TG）单氢过氧化物的初步数据相结合考虑，乳剂的物理性质可能是较小乳剂中氧化稳定性更高的原因，这可能是由于在底物密度更高的较小颗粒内氧化反应的快速终止，而不是由于抗氧化剂生育酚的作用。有望通过进一步研究找到解决DHA等具有多种益处的PUFA氧化这一长期问题的方法。
