浓香菜籽油和精炼菜籽油氧化稳定性 及挥发性成分的差异Differences of oxidative stability and volatile components between fragrant and refined rapeseed oils

利用烘箱法加速氧化试验分析研究浓香菜籽油和精炼菜籽油氧化稳定性及挥发性成分变化的差异。结果显示：基于过氧化值达到国标限量（≤5 mmol/kg）的精炼菜籽油、浓香菜籽油的预测货架期分别为64 d和80 d，浓香菜籽油的氧化稳定性明显优于精炼菜籽油；利用同时蒸馏萃取结合气相色谱-质谱联用法（SDE-GC-MS）对两种菜籽油中挥发性成分进行检测分析发现，在初始浓香菜籽油和精炼菜籽油中分别检出10类84种和6类51种挥发性成分，总量分别为11 110.78 μg/kg和3 831.28 μg/kg；浓香菜籽油中含量最高的是硫苷降解产物，其次是烯烃类和酚类物质，分别占总量的32.04%、22.74%、22.22%；精炼菜籽油中含量最高的是酚类物质，其次是醛类和酮类物质，分别占总量的30.32%、23.18%、16.39%，硫苷降解产物、杂环类、酯类、醇类物质均未检出。35 d的试验结束时，浓香菜籽油和精炼菜籽油中挥发性成分总量均大幅升高，分别为51 729.62 μg/kg和45 671.79 μg/kg，醛类物质成为两种菜籽油中含量最高的挥发性成分，分别占总量的60.30%和68.07%；浓香菜籽油中硫苷降解产物大幅降至仅占总量的2.64%，同时杂环类物质含量大幅降低，酮类、烯烃类、烷烃类物质含量大幅升高；精炼菜籽油中酮类、烷烃类、烯烃类物质含量升高，醇类物质从初始的未检出升高至占总量的13.10%。对挥发性成分进行主成分分析发现，造成两种初始菜籽油差异的挥发性成分主要为苯代丙腈、3-甲基-2-丁腈、2-蒎烯、5-己烯腈、4-乙烯基-2,6-二甲氧基-苯酚，这些物质为浓香菜籽油提供独特风味；在加速氧化试验后期，造成两种菜籽油差异的成分则主要为1-戊烯-3-醇、1-辛烯-3-醇、（E）-2-戊烯醛、(E)-2-庚烯醛、正己醛、壬醛、甲基庚烯酮、(E,E)-3，5-辛二烯-2-酮、白菖烯、甲基环己烯10种物质，且前5种物质与精炼菜籽油相关，多为亚油酸氧化产物，后5种物质则主要与浓香菜籽油相关。研究结果明确了不同工艺生产的菜籽油产品的综合品质差异，可为不同菜籽油产品精准的保质保鲜技术发展提供支持。 An Schaal oven accelerated oxidation experiment was used to examine the differences of oxidative stability and volatile components between fragrant and refined rapeseed oils.The results showed that based on the peroxide value reaching the national standard limit (≤ 5 mmol/kg), the predicted shelf life of refined and fragrant rapeseed oils were 64 d and 80 d, respectively, and the oxidative stability of fragrant rapeseed oil was considerably better than that of refined rapeseed oil. The simultaneous distillation extraction combined with gas chromatography-mass spectrometry (SDE-GC-MS)was used to detect the volatile components in the two kinds of rapeseed oil,and the results revealed that 84 volatile components of 10 categories and 51 volatile components of 6 categories were detected in the initial fragrant rapeseed oil and refined rapeseed oil, respectively, with total amounts of 11 110.78 μg/kg and 3 831.28 μg/kg. The most abundant component in fragrant rapeseed oil was glucosinolate degradation products, followed by alkene and phenols, accounting for 32.04%, 22.74% and 22.22% of the total, respectively. The most abundant component in refined rapeseed oil was phenols, followed by aldehydes and ketones, accounting for 30.32%,23.18% and 16.39% of the total, respectively, while glucosinolate degradation products, heterocyclic, esters and alcohols were not detected. At the end of the 35 d experiment, the total amount of volatile components in fragrant rapeseed oil and refined rapeseed oil increased significantly to 51 729.62 μg/kg and 45 671.79 μg/kg, respectively, and aldehydes became the highest volatile components in both rapeseed oils, accounting for 60.30% and 68.07% of the total, respectively.The glucosinolate degradation products in fragrant rapeseed oil decreased significantly to only 2.64% of the total,while the content of heterocyclic substances was significantly reduced and the contents of ketones, olefins and alkanes significantly increased.The content of ketones, alkanes and olefins in refined rapeseed oil increased, while the content of alcohols increased from the initial non-detect to 1310% of the total. The volatile component principal component analysis revealed that the differences between the two original rapeseed oils were mostly caused by benzoylpropionitrile, 3-methylcrotononitrile, 2-pinene, 5-hexenenitrile and 4-ethenyl-2,6-dimethoxyphenol,which contributed to fragrant rapeseed oil’s unique flavors. In the late stage of accelerated oxidation experiment, the differences between the two rapeseed oils were mainly caused by 1-penten-3-ol, 1-octen-3-ol, (E)-2-pentenal, (E)-2-heptenal, hexanal, nonanal, methylheptenone, (E,E)-3,5-octadien-2-one, leucocalyene and methylcyclohexene, and the first five substances were related to refined rapeseed oil, mostly linoleic acid oxidation products, while the latter five substances were mainly related to fragrant rapeseed oil. The results clarified the comprehensive quality differences of rapeseed oil products produced by different processes and could provide support for the development of precise quality and freshness preservation technology for different rapeseed oil products.