Research Institute of Brewing and Malting, Brewing Institute-Prague, Prague, Czech Republic.
J Agric Food Chem. 2009 Dec 9;57(23):11081-5. doi: 10.1021/jf9028305.
Solid-phase extraction (SPE), solid-phase microextraction (SPME) using carbowax/divinylbenzen fiber, and stir bar sorptive extraction (SBSE) followed by solvent back extraction have been used for the extraction of free fatty acids (caproic, caprylic, pelargonic, capric, lauric, myristic, palmitic, stearic, oleic, linoleic, and linolenic acids) from beer. Subsequent gas chromatographic analyses with flame ionization detection were used for the determination of these compounds. Medium-chain fatty acids (caproic-lauric acid) were determined as free acids, and long-chain fatty acids (myristic-linolenic acids) were determined as methyl esters after methylation by BF(3)-methanol 14%. Linearity, recovery, and repeatability of all methods have been determined and compared with the SPE method used as a reference (SPME method was used only for medium-chain fatty acid determination). All three procedures provide similar working parameters characterized by high repeatability (2.3-16.3%) and good linearity (correlation coefficient ranging from 0.9919 to 0.9999). Results of beer analyses obtained by using these three methods were highly correlated. Although all methods provide compatible alternatives, for medium-chain fatty acid analysis SPME may be a more appropriate technique due to its operational simplicity, repeatability, and low cost.
固相萃取 (SPE)、固相微萃取 (SPME) 使用聚乙二醇/二乙烯基苯纤维和搅拌棒吸附萃取 (SBSE) 后溶剂反萃取已被用于从啤酒中提取游离脂肪酸（己酸、辛酸、壬酸、癸酸、月桂酸、肉豆蔻酸、棕榈酸、硬脂酸、油酸、亚油酸和亚麻酸）。随后使用火焰离子化检测的气相色谱分析用于这些化合物的测定。中链脂肪酸（己酸-月桂酸）被确定为游离酸，长链脂肪酸（肉豆蔻酸-亚麻酸）在 BF(3)-甲醇 14%甲酯化后被确定为甲酯。所有方法的线性、回收率和重复性已经确定，并与用作参考的 SPE 方法进行了比较（仅使用 SPME 方法测定中链脂肪酸）。所有三种方法都提供了类似的工作参数，具有高重复性（2.3-16.3%）和良好的线性（相关系数范围从 0.9919 到 0.9999）。使用这三种方法得到的啤酒分析结果高度相关。尽管所有方法都提供了可替代的方法，但对于中链脂肪酸分析，SPME 可能是一种更合适的技术，因为它操作简单、重复性好且成本低。
