Huimin Lu, Yongfu Li, Ju Qiu
Institute of Integrated Agricultural Development (Guizhou Academy of Agricultural Sciences), Guiyang, China.
College of Food Science and Engineering (Guiyang College), Guiyang, China.
Heliyon. 2024 Feb 29;10(6):e27168. doi: 10.1016/j.heliyon.2024.e27168. eCollection 2024 Mar 30.
Various studies have demonstrated that employing ESR spin trapping to detect free radicals yields valuable insights into the vulnerability of bulk oils to oxidation. Consequently, this method can be employed to assess and compare the oxidative stability of different samples. This study was conducted to investigate the production and transformation of free radicals and trans isomers in linseed oil when subjected to different temperatures and durations of heating. These analyses revealed that the peak levels of free radicals PBN adducts were evident in linseed oil heated to 120 °C, while these levels decreased within 90 min and were absent at a higher temperature of 180 °C. Free radical PBN adducts were readily degraded at 180 °C. Levels of heat-induced trans isomers rose in linseed oil samples with rising temperatures but began to degrade at temperatures exceeding 240 °C partially. The content examination of these trans isomers revealed that the double bonds located at positions 9 and 15 exhibited a higher susceptibility to isomerization compared to the double bond at position 12. Furthermore, the values of and indicated that the synthesis of tri-trans-α-linolenic acid (TALAs) was more challenging compared to double-TALAs, and double-TALAs were more challenging than single-TALAs. This was because the tri-TALAs has a higher E value than the mono-TALAs and double-TALAs. The study has demonstrated that subjecting linseed oil to high-temperature heating leads to the production of free radicals and trans isomers. And PBN radical adduct is unstable at 180 °C and the double bonds at positions 9 and 15 could be isomerized more easily than that at position 12. These results indicated that controlling the formation of free radicals and single-TALAs isomers may be the key way to reduce the trans isomers of linolenic acid during cooking oil heating. In the follow-up study, we found that VE, VK3, ethyl caffeic acid and resveratrol had significant inhibitory effects on the formation of TALAs of linolenic acid, and the highest inhibitory rate of resveratrol with 5% addition could be reached to 30.86%. The above substances can be applied to the thermal processing of linseed oil to prevent the formation of TALAs.
多项研究表明，采用电子自旋共振（ESR）自旋捕集技术检测自由基，能为散装油的氧化易感性提供有价值的见解。因此，该方法可用于评估和比较不同样品的氧化稳定性。本研究旨在调查亚麻籽油在不同温度和加热时长下自由基和反式异构体的产生及转化情况。这些分析表明，在加热至120℃的亚麻籽油中，自由基PBN加合物的峰值水平明显，而这些水平在90分钟内下降，在180℃的较高温度下则不存在。自由基PBN加合物在180℃时很容易降解。随着温度升高，亚麻籽油样品中热致反式异构体的水平上升，但在超过240℃时部分开始降解。对这些反式异构体的含量检测表明，与12位双键相比，9位和15位的双键表现出更高的异构化敏感性。此外， 和 的值表明，与双反式α-亚麻酸（double-TALAs）相比，三反式α-亚麻酸（tri-TALAs）的合成更具挑战性，而双反式α-亚麻酸比单反式α-亚麻酸更具挑战性。这是因为三反式α-亚麻酸的E值高于单反式α-亚麻酸和双反式α-亚麻酸。该研究表明，对亚麻籽油进行高温加热会导致自由基和反式异构体的产生。并且PBN自由基加合物在180℃时不稳定，9位和15位的双键比12位的双键更容易异构化。这些结果表明，控制自由基和单反式α-亚麻酸异构体的形成可能是减少食用油加热过程中亚麻酸反式异构体的关键途径。在后续研究中，我们发现维生素E（VE）、维生素K3（VK3）、咖啡酸乙酯和白藜芦醇对亚麻酸三反式α-亚麻酸（TALAs）的形成有显著抑制作用，添加5%白藜芦醇时最高抑制率可达30.86%。上述物质可应用于亚麻籽油的热加工过程中，以防止三反式α-亚麻酸（TALAs）的形成。
