College of Food Science and Engineering, Henan University of Technology , Zhengzhou 450001, China.
J Agric Food Chem. 2017 May 24;65(20):4167-4176. doi: 10.1021/acs.jafc.7b00858. Epub 2017 May 12.
This research investigated the effects of Fe and antioxidants on the formation of glycidyl esters (GEs) and the free radical mediated mechanisms involving the recognition of cyclic acyloxonium free radical intermediate (CAFRI) for GE formation in both the plant oil model (palm oil, camellia oil, soybean oil, and linseed oil) system and the chemical model (dipalmitin and methyl linoleate) system heated at 200 °C. Results show that Fe can promote the formation of GEs, which can be inhibited by antioxidants in plant oil during high-temperature exposure. Based on the monitoring of cyclic acyloxonium and ester carbonyl group by Fourier transform infrared spectroscopy, the promotion of Fe and the inhibition of antioxidants (tert-butylhydroquinone and α-tocopherol) for GE formation occurred not only through lipid oxidation but also through directly affecting the formation of cyclic acyloxonium intermediate. Additionally, a quadrupole time-of-flight tandem mass spectrometry measurement was conducted to identify the presence of radical adduct captured by 5,5-dimethylpyrroline N-oxide, which provided strong evidence for the formation of CAFRI. Thus, one possible influencing mechanism can be that free radical generated in lipid oxidation may be transferred to dipalmitin and promote CAFRI formation. Fe can catalyze free radical generation while antioxidants can scavenge free radical, and therefore they also can directly affect CAFRI formation.
本研究调查了铁和抗氧化剂对缩水甘油酯 (GEs) 形成的影响，以及涉及循环酰氧鎓自由基中间体 (CAFRI) 识别的自由基介导机制，以研究在 200°C 加热的植物油脂模型（棕榈油、山茶油、大豆油和亚麻籽油）系统和化学模型（二棕榈酸甘油酯和亚油酸甲酯）系统中 GEs 的形成。结果表明，铁可以促进 GEs 的形成，而在高温暴露下，抗氧化剂可以抑制植物油中 GEs 的形成。基于傅里叶变换红外光谱对循环酰氧鎓和酯羰基的监测，Fe 的促进作用和抗氧化剂（叔丁基对苯二酚和α-生育酚）对 GEs 形成的抑制作用不仅通过脂质氧化发生，而且还通过直接影响循环酰氧鎓中间体的形成。此外，进行了四极杆飞行时间串联质谱测量，以鉴定由 5,5-二甲基吡咯烷 N-氧化物捕获的自由基加合物，这为 CAFRI 的形成提供了有力证据。因此，一种可能的影响机制可能是脂质氧化中产生的自由基可能转移到二棕榈酸甘油酯并促进 CAFRI 的形成。铁可以催化自由基的生成，而抗氧化剂可以清除自由基，因此它们也可以直接影响 CAFRI 的形成。
