Monoacylglycerols derived from butter oil by Penicillium roquefortii in suspension cultures

Structural isomers of monoacylglycerols (monoglycerides, MAGs) were identified and compared after degradation of butter oil by two strains of Penicillium roquefortii and a commercial lipase from P roquefortii (EC 3.1.1.3) at pH 7.0 and 10 °C. The conditions were selected as they were comparable with those used in the manufacture of blue mould‐ripened cheese. The commercial lipase was selected to compare with the fungal strains in terms of acyl migration. Results showed that the main isomers formed by lipolysis with the commercial lipase were sn‐2 MAGs (64 mol%), whilst spores and emerging mycelia of P roquefortii produced mainly sn‐1(3) MAGs (83–90 mol%). The work reported here may lead to further assessment of different MAG structural isomers as natural preservatives in foods and dairy products. © 2002 Society of Chemical Industry     

Solid–Liquid Phase Behaviors of Binary Mixtures of Various Partial Acylglycerols by Differential Scanning Calorimetry

Monoacylglycerol (MAG), diacylglycerol (DAG), and triacylglycerol (TAG) are impurities in biodiesel and a major cause of precipitation. Understanding the behavior of such acylglycerols is essential for predicting biodiesel cold flow properties (CFPs). The previous study on MAG/MAG binary mixtures shows that they tend to solidify by forming molecular compounds. In contrast, TAG/TAG mixtures, which have been studied extensively, are commonly eutectic or monotectic systems, in which each component solidifies separately. The present study focuses on binary mixtures of DAG/DAG and different acylglycerol pairs (MAG/DAG, TAG/MAG, and DAG/TAG), and determination of their solid–liquid phase behavior by differential scanning calorimetry. These mixtures are found to behave as eutectic or monotectic systems with no sign of compound formation. As DAG and TAG have lower contents than MAG in biodiesel and they are unlikely to form molecular compounds with MAG, it is suggested that DAG and TAG have little effect on the biodiesel CFPs. Practical Applications: Biodiesel has attracted much interest because its blending with conventional fossil diesel has become more standard with biofuel mandates. From an energy perspective, the solid–liquid phase behavior of acylglycerols will contribute to building prediction models for biodiesel CFPs.     

Evidence of Strict Stereospecificity in the Structure of sn‐1,2‐Diacyl‐3‐Acetyl‐Glycerols from Euonymus maximowiczianus Seeds Using Nuclear Magnetic Resonance Spectroscopy

Asymmetric, optically active sn‐1,2‐diacyl‐3‐acetyl‐glycerols (AcDAG) have been known to scientists for several decades. However, to date, the problem of their structure has not been definitely resolved, which has led to a vast diversity of terms used for their designation in the literature. Using two‐dimensional nuclear magnetic resonance, we have investigated AcDAG from the mature seeds of Euonymus maximowiczianus, from which we have been able to both identify a correlation of the methyl group in acetic acid residue with protons at the carbon atom at sn‐3 position in the glycerol residue of the AcDAG molecule and, for the first time, demonstrate that this correlation is observed exclusively with one carbon atom at the α‐position, but not with two as would have been expected in case of a racemic mixture. Moreover, results of our analysis of AcDAG isolated from the seeds of E. maximowiczianus directly confirm that diacylglycerol‐3‐acetyl‐transferase is responsible for their biosynthesis, which reveals a strict specificity not only to acetyl‐CoA as one of the substrates but also to the sn‐3‐position of the glycerol residue in sn‐1,2‐diacylglycerol during their biosynthesis.     

响应面试验优化阿魏酰基脂肪酰基结构酯合成工艺及产物稳定性

利用响应面试验对在溶剂体系中脂肪酶Lipozyme RM IM催化玉米胚芽油与阿魏酸酸解制备阿魏酰基脂肪酰基结构酯的反应条件进行优化。在摇床转速为220 r/min的条件下,选取投料比（阿魏酸与玉米胚芽油质量比）、反应温度、反应时间3 个因素作为考察对象,以阿魏酸转化生成阿魏酰基脂肪酰基结构酯的得率为考察指标,运用Design-Expert软件的星点设计功能进行试验设计并对结果进行分析。结果表明,3 个因素均为影响阿魏酸酯化的显著因素;经响应面分析可确定最优值为投料比8.9∶1（g/g）、反应温度76.0 ℃、反应时间28.1 h。该条件下的平均得率达59.1%,与响应面拟合方程的得率预测值58.8%吻合良好。在煎炸过程中新制备的结构酯产生较低的聚合物,同时其具有较高的贮藏稳定性。     

高温气相色谱分析甘油酯的研究

建立了高温气相色谱分析油脂样品中脂肪酸和甘油酯含量的方法.采用保留时间定性,外标法定量,定性定量准确.得到的脂肪酸、单甘酯、甘油二酯、甘油三酯的标准曲线,在质量浓度范围0.5～20.0 mg/mL内峰面积与被测物质量浓度线性关系良好.加样回收试验表明,平均加样回收率在95.69%～105.78%之间,RSD在0.27%～2.98%之间.用该方法分析各种脂肪酸和甘油酯均有较好的精密度和重复性.     

Identification of TAG and DAG and their FA Constituents in Lesquerella (Physaria fendleri) Oil by HPLC and MS

Castor oil has many industrial uses because of its high content (90 %) of the hydroxy fatty acid, ricinoleic acid (OH¹²18:1⁹). Lesquerella oil containing lesquerolic acid (Ls, OH¹⁴20:1¹¹) is potentially useful in industry. Ten molecular species of diacylglycerols and 74 molecular species of triacylglycerols in lesquerella (Physaria fendleri) oil were identified by electrospray ionization mass spectrometry as lithium adducts of acylglycerols in the HPLC fractions of lesquerella oil. Among them were: LsLsO, LsLsLn, LsLsL, LsLn–OH20:2, LsO–OH20:2 and LsL–OH20:2. The structures of the four new hydroxy fatty acid constituents of acylglycerols were proposed by the MS of the lithium adducts of fatty acids as (comparing to those in castor oil): OH¹²18:2^9,14 (OH¹²18:2^9,13 in castor oil), OH¹²18:3^9,14,16 (OH18:3 not detected in castor oil), diOH^12,1318:2^9,14 (diOH^11,1218:2^9,13 in castor oil) and diOH^13,1420:1¹¹ (diOH20:1 not detected in castor oil, diOH^11,1218:1⁹ in castor oil). Trihydroxy fatty acids were not detected in lesquerella oil. The differences in the structures of these C18 hydroxy fatty acids between lesquerella and castor oils indicated that the polyhydroxy fatty acids were biosynthesized and were not the result of autoxidation products.     

Changes in enzymic hydrolysis in vitro of thermoxidised canola oil

The hydrolysis of fractionated products from thermoxidised canola oil by pancreatic lipase was investigated in relation to chemical changes in the acylglycerols. After 70 h of heating, the amount of hydrolysis of the acylglycerol dimers was only about half, and that for the trimers about one-third, that of the monomers. The higher polymers were the least hydrolysed and showed no further reaction after 5 min. The reduction in enzymic hydrolysis of isolated fractions from the thermoxidised oils indicates structural differences, related to formation of polar compounds and polymerisation products.     

Quantitative analysis of partial acylglycerols and free fatty acids in palm oil by 13C nuclear magnetic resonance spectroscopy

The chemical shifts, spin-lattice relaxation times (T ₁), and one-bond C−H coupling constants of the glycerol carbons of mono-, di-, and triacylglycerols in CDCI₃ solution are presented and discussed. The glycerol carbons have low T ₁ values (<1.0 s) and full nuclear Overhauser effect and also exhibit broader linewidths than the aliphatic carbons, suggesting that the glycerol carbons are at or near the T ₁ minimum for the dipole-dipole relaxation mechanism. Therefore, for quantitative measurement of the composition of partial acylglycerols (relative to the triacylglycerols) in palm oil, the nuclear magnetic resonance (NMR) spectrum of the β-carbons, which lie exclusively in the region δ68.3–72.1 ppm, should preferably be acquired at medium or low magnetic fields and at an elevated temperature in order to ensure that the condition for extremely narrow spectral lines is satisfied. The chemical shifts and spinlattice relaxation times of the aliphatic C-2 and C-3 carbons and of the carbonyl carbons (C-1) of acyl groups present in palm oil are also presented and discussed. The presence of free fatty acid in the palm oil is easily detected and quantified in the spectrum of the aliphatic carbons. The presence of partial acylglycerols in palm oil can also be detected and/or quantified in the NMR spectra of the C-2 and the carbonyl carbons. The quantitative analysis of the glycerol carbons of a known mixture of acylglycerols obtained by using this method is presented.     

Content and Fatty Acid Composition of Neutral Acylglycerols in Euonymus Fruits

The content and fatty acid (FA) composition of FA neutral acylglycerols (NAG), a mixture of 1,2,3-triacyl-sn-glycerols (TAG) and 3-acetyl-1,2-diacyl-sn-glycerols (acDAG), were determined in the seeds and arils of fruits of 14 Euonymus L. species. On the average, the seeds exceeded the arils in the absolute and relative dry matter content 2.9- and 1.9-fold, respectively, and separate plant species greatly differed in NAG composition. The proportions of TAG in the NAG of seeds and arils were 4–5 and ~98 %, respectively. The degree of FA unsaturation in aril NAG was higher than in the seed NAG, and in acDAG—higher, than in TAG. In the NAG, 14 major FA molecular species (excluding minor FA) were found, and linoleic, oleic, palmitic, and linolenic acids were predominant. NAG of separate taxonomic units of the genus Euonymus L. differed from each other in the concentration of major FA as well as other FA. So, by using statistical analysis, it was definitely established that the species from the subgenus Euonymus were characterized by an increased content of linoleic acid, while those from the subgenus Kalonymus, by the predominance of oleic acid. Meanwhile, the species of the section Euonymus were marked by an enhanced concentration of a number of hexa- and octadecenoic FA positional isomers.