加热对食用植物油中短链脂肪酸含量的影响

Effect of heating on short chain fatty acid content in edible vegetable oil

目的建立气相色谱-质谱法(GC-MS)直接分析植物油中短链脂肪酸,研究食用植物油经高温加热后油脂短链脂肪酸的含量变化。方法经高温加热的正常食用植物油样品利用皂化、酸化、萃取的方法,提取短链脂肪酸,GCMS定性、定量分析。结果正己酸、正庚酸、辛酸在各自的线性范围内线性关系良好,相关系数分别为0.999 4、0.998 9、0.996 4。以峰面积对样品的浓度建立线性回归方程,检出限分别为2.73×10^(-3)μg/ml、4.07×10^(-3)μg/ml、2.33×10^(-2)μg/ml,定量限分别为9.11×10^(-3)μg/ml、1.36×10^(-2)μg/ml、7.76×10^(-2)μg/ml。结论本法操作简便、快速、准确、检出限低,可用于植物油中短链脂肪酸的检测。食用植物油中的短链脂肪酸的含量与其加热程度、次数密切相关。本法有望作为煎炸老油鉴别的特异方法,同时对地沟油的鉴别检测也有一定的借鉴作用。

Objective To establish a method for the determination of short chain fatty acids in edible vegetable oil by gas chromatography-mass spectrometry（ GC-MS）,and to study the content changes of short chain fatty acids in edible vegetable oil heated by high temperature. Methods The normal edible vegetable oil samples heated by high temperature were processed by saponification,acidification and extraction,and the short chain fatty acids was extracted and analyzed qualitatively and quantitatively by GC-MS. Results Good linearity was obtained when the concentrations of caproic acid,heptylic acid and octanoic acid were within their linear ranges,with the correlation coefficient（ r） of 0. 999 4,0. 998 9 and 0. 996 4,respectively. Linear regression equation of the sample concentration was established with the peak area,and the limit of detection（ LOD） of caproic acid,heptylic acid and octanoic acid was 2. 73 × 10^-3μg /ml,4. 07 × 10^-3μg /ml,2. 33 × 10^-2μg /ml and the limit of quantitation（ LOQ） was 9. 11 × 10^-3μg /ml,1. 36 × 10^-2μg /ml,7. 76 × 10^-2μg /ml,respectively. Conclusion The method is simple,rapid,accurate with low detection limit. It can be used for the detection of short chain fatty acids in vegetable oil. The short chain fatty acid content is related to both degrees of temperature and times of heating. This method can be expected to a specific identification method of the fried oil and taken as a method for the detection of oil groove in reference.