高油酸油脂在贮藏和加热过程中醛类的演变规律Evolution of aldehydes in high oleic acid oil during storage and heating

为探究温度对高油酸油脂中醛类化合物形成的影响规律及其作为油脂氧化评价指标的可行性，选取典型高油酸油脂（橄榄油和山茶油）为试验对象，分别进行冷藏(4 ℃)和室温(26 ℃)贮藏12个月以及90、150、210 ℃加热处理12 h，分析处理过程中5种醛类物质（壬醛、辛醛、癸醛、反式-2-癸烯醛和反式-2-十一烯醛）含量的变化规律及可能的形成机制，并与传统油脂氧化评价指标进行相关性分析。结果表明：冷藏和室温贮藏时，饱和醛的生成占主导，尤其是壬醛的增量显著；加热处理时，随加热温度升高不饱和醛逐渐占据优势，反式-2-癸烯醛和反式-2-十一烯醛的增长逐渐加剧；基于油酸自动氧化理论，壬醛的产生主要由9-ROOH和10-ROOH两种氢过氧化物的裂解导致，反式-2-癸烯醛和反式-2-十一烯醛则分别为9-ROOH和8-ROOH氢过氧化物的裂解产生；相关性分析表明，油脂贮藏时特征醛与总氧化值线性相关，加热处理时不饱和特征醛类与茴香胺值线性相关。因此，高油酸油脂氧化过程中所产生的醛类物质含量和种类与温度密切相关，醛类物质可以作为油脂氧化程度评价的新指标，结合传统油脂氧化评价指标，能更全面评价油脂的初级和次级氧化程度。In order to explore the influence of temperature on the formation of aldehydes in high oleic acid oil and its feasibility as an evaluation index of oil oxidation, typical high oleic acid oils (olive oil and oil-tea camellia seed oil) were selected as experimental objects, and they were stored at fridge (4 ℃) and room (26 ℃) for 12 months and heated at 90, 150 ℃ and 210℃ for 12 h,and the variation rules of the contents of five aldehydes (nonanal, octanal, decanal, trans-2- decenal and trans-2- undecenal) during the treatment and possible formation mechanism were analyzed. In addition, the correlation between aldehydes and traditional oil oxidation evaluation indexes was analyzed.The results showed that saturated aldehydes were dominant when stored at fridge and room, especially nonanal had a significant increase. During heating treatment, with the increase of heating temperature, unsaturated aldehydes took the dominant status gradually, the growth rate of trans-2- decenal and trans-2-undecenal progressively increased. Based on the oleic acid auto-oxidation theory, the production of nonanal was mainly caused by the cracking of 9-ROOH and 10-ROOH hydroperoxides. Trans-2- decenal and trans-2- undecenal were produced by the cracking of 9-ROOH and 8-ROOH hydroperoxides, respectively. The correlation analysis found that characteristic aldehydes were linearly related to the total oxidation value during oil storage and unsaturated characteristic aldehydes were linearly related to p-anisidine value during heating treatment. Therefore, the content and types of aldehydes produced in the oxidation process of high oleic acid oil were closely related to temperature. Aldehydes can be used as a new index for the evaluation of oil oxidation degree, and combined with traditional oxidative evaluation indexes, the primary and secondary oxidation degree of oil can be more comprehensively evaluated.