不同预处理方法对检测食醋中丁酸含量的影响

The effect of different pretreatment methods on determination of butyric acid in vinegars

以米醋、陈醋、香醋、小米醋和白醋为食醋样品,分别用乙醚萃取法、甲酯化-正己烷法、甲酯化-二氯甲烷法等3种不同的方法进行预处理,采用气相色谱法(GC)分析加标醋样中的丁酸含量。从保留时间、峰型、准确度、精密度、线性、检出限和检测限等方面对结果进行分析,比较不同方法对丁酸定量分析的影响,并确定最适合的丁酸含量检测方法。通过对实验结果分析发现:经12.5%硫酸-甲醇溶液甲酯化与二氯甲烷萃取结合的方法处理丁酸标准品后的保留时间为9.50 min,峰型好、响应值最高;利用该方法对5种加标样品中的丁酸进行预处理,得到的回收率在87.36%~106.52%,相对标准偏差最低,范围为0.24%~4.31%,该方法的检测限为0.043 mg/mL,检出限为0.011 mg/mL。因此,甲酯化-二氯甲烷是3种方法中比较适合气相检测食醋中丁酸含量的方法,将其应用到富丁酸醋的发酵过程中检测丁酸含量变化,发现在10 d的发酵过程中,丁酸含量整体呈上升趋势,变化范围为1.31~2.36 mg/mL。本研究为今后相关产品的开发与利用奠定了基础。

To select the optimal pretreatment method for determination of butyric acid(BA)in vinegar,three different techniques,including ether-extraction,methyl-esterification with n-hexane,and methyl-esterification with dichloromethane,were compared.Five samples,such as rice vinegar,mature vinegar,white vinegar,millet vinegar and balsamic vinegar,were spiked with three concentrations of BA,and were analyzed using gas chromatography(GC)after pretreatment.Several parameters including retention time,peak shape,accuracy,precision,linearity,limit of detection(LOD),and limit of determination(LOQ)were analyzed.The result reveals that,the retention time of standard treated with methyl-esterification equipped with dichloromethane method was 9.50 min with the highest respond and peak symmetry,and there was no any interference peak around the retention time.The highest recovery scope(87.36%~106.52%)was obtained with the lowest relative standard deviation(0.24%~4.31%).LOQ and LOD were 0.043 mg/mL and 0.011 mg/mL,respectively.Therefore,the method was selected to applied in the determination of BA in butyric acid-rich vinegar.During 10-days fermentation,an increasing trend was observed:the concentration of BA increased from 1.31 mg/mL to 2.36 mg/mL.This study laid the foundation for further development of relative products.