在甘油三酯和磷脂分离后，对奶酪样品中的脂肪酸甲酯和磷脂进行定量分析。

Quantification of fatty acids as methyl esters and phospholipids in cheese samples after separation of triacylglycerides and phospholipids.

作者信息

Hauff Simone, Vetter Walter

机构信息

University of Hohenheim, Institute of Food Chemistry, Garbenstrasse 28, D-70599 Stuttgart, Germany.

出版信息

Anal Chim Acta. 2009 Mar 23;636(2):229-35. doi: 10.1016/j.aca.2009.01.056. Epub 2009 Feb 5.

DOI:10.1016/j.aca.2009.01.056

PMID:19264173

Abstract

Determination of the individual fatty acid composition of neutral- and phospholipids as well as the phospholipid content of dairy food and other foodstuffs are important tasks in life sciences. For these purposes, a method was developed for the separation of lipids (standards of triolein and diacylphosphatidylcholines as well as three cheese samples) by solid-phase extraction using a self-packed column filled with partly deactivated silica. Non-halogenated solvents were used for the elution of the lipid classes. Cyclohexane/ethyl acetate (1:1, v/v) served for the elution of neutral lipids, while polar lipids were eluted with three solvents (ethyl acetate/methanol, methanol, and methanol/water) into one fraction. The separated lipid fractions were transesterified and the individual fatty acids were quantified by using gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS) in the selected ion monitoring (SIM) mode. The recovery rate for standard phosphatidylcholines was approximately 90% and cross-contamination from neutral lipids was negligible. The method was applied to cheese samples. Quantitative amounts of individual fatty acids in the phospholipid fraction were <0.002-0.29% of total lipids from camembert, <0.002-0.12% of total lipids from mozzarella, and <0.002-0.18% of total lipids in a goat cream cheese. Differences in the fatty acid pattern of neutral and polar lipids were detected. The quantity of the fatty acids determined in the phospholipid fraction was divided by the factor 0.7 in order to convert the fatty acid content into the phospholipid content of the cheese samples. This factor is based on the contribution of 16:0 to dipalmitoylphosphatidylcholine (DPPC). The resulting DPPC equivalents (DPPC(eq)) were found to be representative for the average contribution of fatty acids to all classes of phospholipids in dairy products. Using this approach, the phospholipid content of lipids from mozzarella, camembert, and goat cream cheese was 0.60%, 1.42% and 0.79%, respectively.

摘要

测定乳制品及其他食品中中性脂和磷脂的脂肪酸组成以及磷脂含量是生命科学中的重要任务。为此，开发了一种通过固相萃取分离脂质的方法（使用填充有部分失活硅胶的自装柱，以三油酸甘油酯和二酰基磷脂酰胆碱标准品以及三个奶酪样品作为分析对象）。使用非卤化溶剂洗脱脂质类别。环己烷/乙酸乙酯（1:1，v/v）用于洗脱中性脂质，而极性脂质则用三种溶剂（乙酸乙酯/甲醇、甲醇、甲醇/水）洗脱为一个馏分。将分离得到的脂质馏分进行酯交换反应，然后采用气相色谱-电子电离质谱联用仪（GC/EI-MS）在选择离子监测（SIM）模式下对各个脂肪酸进行定量分析。标准磷脂酰胆碱的回收率约为90%，中性脂质的交叉污染可忽略不计。该方法应用于奶酪样品分析。卡芒贝尔奶酪中磷脂馏分中各脂肪酸的定量含量占总脂质的<0.002 - 0.29%，马苏里拉奶酪中占<0.002 - 0.12%，山羊奶油奶酪中占<0.002 - 0.18%。检测到中性脂和极性脂的脂肪酸模式存在差异。为了将磷脂馏分中测定的脂肪酸含量换算为奶酪样品中的磷脂含量，需将脂肪酸含量除以0.7这个系数。该系数基于16:0对二棕榈酰磷脂酰胆碱（DPPC）的贡献。结果发现，得到的DPPC当量（DPPC(eq)）能够代表脂肪酸对乳制品中所有磷脂类别的平均贡献。采用这种方法，马苏里拉奶酪、卡芒贝尔奶酪和山羊奶油奶酪中脂质的磷脂含量分别为0.60%、1.42%和0.79%。