豉香型白酒中的高级脂肪酸乙酯的形成机理和影响其生成的因素

在豉香型白酒的发酵过程中,高级脂肪酸乙酯的形成机理分三个阶段,第一阶段大米和曲中的黄豆作为原料在酵母的作用下产生高级脂肪酸乙酯;第二阶段主要通过醪液中各种酶的作用下,生物合成脂肪酸,然后脂肪酸与乙醇酯化成高级脂肪酸乙酯;第三阶段高级脂肪酸乙酯在酸性环境中水解成高级脂肪酸和乙醇,脂肪含量高的原料生成的高级脂肪酸乙酯多,含有较多的有机氮源的原料,对发酵过程高级脂肪酸乙酯的形成有促进作用。     

α-亚麻酸乙酯的富集纯化及工艺研究

亚麻籽油经乙酯化得到混合高级脂肪酸乙酯,采用冷冻结晶法和尿素包合法对混合高级脂肪酸乙酯进行纯化,得到高纯度的α-亚麻酸乙酯。考察了尿素包合过程中尿素的用量、溶剂乙醇的用量、结晶温度、结晶时间等单因素对纯化效果的影响。并由正交试验确定了包合过程的最佳工艺条件。研究发现：当m（脂肪酸乙酯）∶m（尿素）∶V（乙醇）为1.5∶4∶6、结晶温度0℃、结晶时间16 h时,α-亚麻酸乙酯的含量可以提高到89%以上,得率可以达到60%以上。     

低温溶剂结晶法富集鸦胆子油不饱和脂肪酸乙酯

以鸦胆子油为原料，经醇解制得脂肪酸乙酯，采用低温溶剂结晶法富集不饱和脂肪酸乙酯，以不饱和脂肪酸乙酯含量、得率为评价指标，分别考察溶剂种类、结晶温度、结晶时间、溶剂与脂肪酸乙酯体积比以及结晶次数对分离效果的影响。结果表明，低温溶剂结晶法富集鸦胆子油不饱和脂肪酸乙酯的最佳条件为：乙醇作为溶剂，溶剂与脂肪酸乙酯体积比3∶ 1，结晶温度-20 ℃，结晶时间7 d，结晶次数2次。在最佳条件下，鸦胆子油脂肪酸乙酯中不饱和脂肪酸乙酯含量由86.49%升高至95.32%，得率为85.4%。     

米糠油脱臭馏出物乙酯化工艺条件研究

为综合利用米糠油脱臭馏出物提取生育酚和生育三烯酚,同时得到可用于医药和食品工业的脂肪酸乙酯,本文研究米糠油脱臭馏出物乙酯化最佳工艺条件。试验结果表明,米糠油脱臭馏出物乙酯化的最佳工艺条件为：脂肪酸：乙醇（mol/mol）1∶5;反应时间2.5h;温度75℃;浓硫酸：原料（wt%）3%。在该条件下,脂肪酸乙酯化率达到97.02%,VE保存率达98.48%。     

湖北乌桕脂中脂肪酸的色谱─—质谱联用分析

以硫酸为催化剂，用乌桕脂和乙醇进行酯交换反应合成脂肪酸乙酯。再进行ＧＣ／ＭＳ分析，定性及半定量地测得各脂肪酸的成份，特别检出了乌桕脂中含有奇数碳的脂肪酸存在。     

湖北乌桕脂中脂肪酸的色谱—质谱联用分析

以硫酸为催化剂，用乌桕脂和乙醇进行酯交换反应合成脂肪酸乙酯。再进行ＧＣ／ＭＳ分析，定性及半定量地测得各脂肪酸的成份，特别检出了乌桕脂中含有奇数碳的脂肪酸存在。     

响应面法优化大豆油脂肪酸乙酯合成工艺

以大豆油为原料,KOH作催化剂,通过大豆油与乙醇的酯交换反应合成了大豆油脂肪酸乙酯。应用响应曲面分析法中的Box-behnken模型对影响大豆油脂肪酸乙酯转化率的四个主要因素（催化剂用量、醇油摩尔比、反应温度、反应时间）进行了优化。研究表明大豆油脂肪酸乙酯的最佳合成工艺条件为：KOH用量1.3%,醇油比8.3∶1,反应温度74.8℃,反应时间130min。在此条件下,酯转化率达98.93%。     

蔗糖酯型表面活性剂的合成工艺研究

以天然棉籽油,制糖厂的副产品乙醇来制取棉籽油脂肪酸乙酯,进一步通过棉籽油脂肪酸乙酯与蔗糖进行均相熔融酯交换反应生成蔗糖脂肪酸酯。以配料比、皂用量、催化剂用量、反应温度、反应时间构建了五因子四水平正交试验,通过产率、单酯含量和亲水亲油平衡(HLB)值的结果分析,确定了蔗糖棉籽油脂肪酸酯的最佳合成方案:蔗糖∶脂肪酸乙酯=1∶0.8;催化剂用量为2%;皂用量为15%;反应温度控制在135℃;反应时间为2h,在此基础上进行了单因素影响延伸试验,确定各影响因素的影响程度及顺序。     

大豆油脂肪酸乙酯的制备及其在印刷油墨中的应用

以大豆油为原料,在催化剂KOH作用下,探讨大豆油与乙醇进行酯交换反应工艺,并对大豆油脂肪酸乙酯在印刷领域的应用进行论述。研究表明,在乙醇用量超过理论计算值的65％,催化剂用量为油重1．3％,反应时间2h,反应温度76-77℃条件下,酯交换反应转化率可达98．67％,且产物黏度和相对分子质量接近矿物油水平。其优异的溶解性能,安全的生产工艺和环保特性,表明大豆油脂肪酸乙酯在油墨中的应用潜力。     

大豆油脂肪酸乙酯的合成与精制工艺研究

以甲醇钠催化乙醇和大豆油发生酯交换反应合成大豆油脂肪酸乙酯,并采用氯化胆碱和尿素制备的低共熔溶剂(DES)对产品进行精制。通过正交实验得到酯交换反应的优化工艺条件为:催化剂用量1.3%,醇油摩尔比8∶1,反应温度65℃,反应时间3 h。在此条件下,大豆油转化率达到99.38%。通过正交实验得到DES精制大豆油脂肪酸乙酯的最优工艺条件为:DES用量(以与大豆油脂肪酸乙酯体积比表示)1∶1,洗涤温度75℃,洗涤时间4 min。在此条件下,大豆油脂肪酸乙酯产品中甘油残留量为0.017%,pH为7.0,且无废水排放。     

基于植物油中脂肪酸烷基酯含量变化鉴别废弃油脂

采用固相萃取柱净化,气相色谱-质谱联用法测定了6种植物油中脂肪酸烷基酯(包括脂肪酸甲酯和脂肪酸乙酯)的含量,并研究其在植物油煎炸、废弃及废弃油脂精炼等环节中的变化。结果发现,6种植物油中脂肪酸烷基酯的含量均低于30 mg/kg,而植物油在废弃过程中可能会形成大量脂肪酸乙酯,生成量与油脂是否烹饪及废弃物中乙醇含量有关。脂肪酸烷基酯在脱色工艺中不能被去除,但在脱臭中可被去除。因此,可以通过测定植物油中脂肪酸烷基酯含量发现废弃油脂,为废弃油脂的鉴别工作提供新的思路。     

Supercritical fluid fractionation of fatty acid ethyl esters from butteroil

Countercurrent supercritical fractionation of the fatty acid ethyl esters from butteroil has been investigated. The main objective of the present study was to obtain extracts rich in short- and medium-chain fatty acid ethyl esters. To that end, transesterification of the original butteroil was used to transform the triacylglycerols into the corresponding fatty acid ethyl esters. Then, several supercritical fluid extractions were carried out at pressures ranging from 8.9 to 18.6 MPa and at 2 different temperatures (48 and 60°C). The flow ratio of CO₂ to butteroil was 15. Composition and yield of short- and medium-chain fatty acid ethyl esters was evaluated at different extraction conditions. Extracts containing ∼70% short- and medium-chain fatty acid ethyl esters were obtained at 101 bar and 60°C, and can be used as starting material for the production of highly valuable functional lipids.     

气相色谱-内标法测定白酒中3种高级脂肪酸乙酯含量

以乙酸正戊酯为内标物,建立了白酒中棕榈酸乙酯、油酸乙酯和亚油酸乙酯的气相色谱-内标法检测方法,并对市售不同香型白酒、不同品牌酱香型白酒中3种高级脂肪酸乙酯的含量分布规律进行探究。结果表明,3种高级脂肪酸乙酯的分离效果良好,线性范围为0.300 0～0.400 0 mg/mL,相关系数（R2）均＞0.999,精密度试验结果相对标准偏差（RSD）＜5%,加标回收率为94.01%～116.97%,检出限为0.003 2～0.003 5 mg/mL,定量限为0.010 9～0.011 7 mg/mL。11种不同香型白酒样品的3种高级脂肪酸乙酯含量在0～0.062 2 mg/mL之间,其中,酱香型白酒含量最高（0.062 2 mg/mL）;35种不同品牌酱香型白酒中3种高级脂肪酸乙酯总含量在0.003 5～0.075 8 mg/mL之间。该方法准确、灵敏度高,能对白酒中3种高级脂肪酸乙酯进行有效的分析,可用于酒类企业日常白酒分析检测。     

The yeast enzyme Eht1 is an octanoyl‐CoA:ethanol acyltransferase that also functions as a thioesterase

Fatty acid ethyl esters are secondary metabolites that are produced during microbial fermentation, in fruiting plants and in higher organisms during ethanol stress. In particular, volatile medium‐chain fatty acid ethyl esters are important flavour compounds that impart desirable fruit aromas to fermented beverages, including beer and wine. The biochemical synthesis of medium‐chain fatty acid ethyl esters is poorly understood but likely involves acyl‐CoA:ethanol O‐acyltransferases. Here, we characterize the enzyme ethanol hexanoyl transferase 1 (Eht1) from the brewer's yeast Saccharomyces cerevisiae. Full‐length Eht1 was successfully overexpressed from a recombinant yeast plasmid and purified at the milligram scale after detergent solubilization of sedimenting membranes. Recombinant Eht1 was functional as an acyltransferase and, unexpectedly, was optimally active toward octanoyl‐CoA, with k_cat = 0.28 ± 0.02/s and K_M = 1.9 ± 0.6 μm . Eht1 was also revealed to be active as a thioesterase but was not able to hydrolyse p‐nitrophenyl acyl esters, in contrast to the findings of a previous study. Low‐resolution structural data and site‐directed mutagenesis provide experimental support for a predicted α/β‐hydrolase domain featuring a Ser–Asp–His catalytic triad. The S. cerevisiae gene YBR177C/EHT1 should thus be reannotated as coding for an octanoyl‐CoA:ethanol acyltransferase that can also function as a thioesterase. © 2014 The Authors. Yeast published by John Wiley & Sons, Ltd.     

Ester synthesis by lactic acid bacteria isolated from goat’s and ewe’s milk and cheeses

The present work evaluates the ability of lactic acid bacteria isolated from goat’s and ewe’s milk and cheeses to synthesise short-chain fatty acid esters. In order to elucidate the mechanisms of ester synthesis involved, cell-free extracts were incubated in sodium phosphate buffer containing triglyceride plus ethanol (alcoholysis) and free fatty acid plus ethanol (esterification). After 24 h incubation at 37 °C esters were extracted and determined by gas chromatography. Strains evaluated were able to synthesise ethyl esters from 2 to 10 carbon atoms, mainly ethyl butanoate and ethyl hexanoate. A great variability amongst strains was observed. In general, higher ester-forming activities by esterification were detected. In enterococci strains the alcoholysis mechanism was also involved.     

降低高度不饱和脂肪酸乙酯中的过氧化值方法的研究

以LiAlH_4为还原剂,试图降低富含高度不饱和脂肪酸乙酯(主要是5、8、11、14、17、——廿碳五烯酸乙酯,5、8、11、14、17、20——廿二碳六烯酸乙酯。分别简称为EPA乙酯,DHA乙酯)的鱼油酸乙酯的过氧化值。其中,以乙醚为溶剂,LiAlH_4的用量为3％,反应时间为60～90min,去过氧化值的效果显著,方法较简便。     

酯水解行为与其烷基极化效应指数关系和酯与阿拉伯胶缔合行为的研究和应用

本文运用电导法测定了不同浓度的乙醇溶液中脂肪酸酯的水解速率常数(k),并对脂肪酸乙酯类化合物的分子结构、水解条件与k的关系进行了相关分析,并推导得出酯类化合物k与烷基极化效应指数PEI(R)及体系介电常数(ε)间的关系表达式:lgk=a+blgPEI(R)+clgε,为研究酯水解机理主要影响因素、预测其k和判断酯的结构提供了一定的理论依据。同时研究了38%(V/V)乙醇溶液中阿拉伯胶(简称GA)与脂肪酸酯之间的缔合行为,并建立了定量确定缔合常数(A)的方法,推导并验证了定量表达酯水解速率常数k与GA浓度(M)关系的数学表达式:k’=k/(1+AM),得出了GA对脂肪酸酯水解起禁阻作用的结论。其研究结果用于38°清香型汾酒稳定性的提高取得了令人满意的效果。     

Optimisation of enzymatic esterification of soybean oil deodoriser distillate

The enzymatic esterification of free fatty acids from soybean oil deodoriser distillate with ethanol, catalysed by immobilised fungal lipase, was studied. The extent of conversion of free fatty acids to ethyl esters was optimised using a response surface methodology obtained through a second‐order factorial experimental design. The variables studied were reaction temperature (30–70 °C), enzyme concentration (7–23%) and ethanol/free fatty acid molar ratio (0.3–3.7:1). The optimal reaction conditions achieved were temperature from 46.4 to 53.6 °C, enzyme concentration from 13.6 to 16.5% and ethanol/free fatty acid molar ratio from 1.7 to 2.3:1, with conversions above 88%. No significant tocopherol losses were observed during the process. In conclusion, enzymatic fatty acid esterification was shown to be a technically viable process. © 2001 Society of Chemical Industry     

光皮树籽抽出物的成分分析

为了分析光皮树籽抽提物的化学成分,采用无水乙醇、丙酮、正己烷、石油醚和乙酸乙酯分别抽提光皮树籽,抽出物经活性炭脱色后进行GC-MS 分析。结果发现,无水乙醇和丙酮抽出物中主要含有游离的棕榈酸、油酸和亚油酸,其中亚油酸相对含量最高,达到52% 以上,油酸相对含量最低,不超过8.2%。正己烷、石油醚和乙酸乙酯抽出物中甘三酯的脂肪酸组成主要是棕榈酸、硬脂酸、油酸和亚油酸,其中油酸相对含量最高,达到42% 以上,其次是亚油酸,总不饱和脂肪酸相对含量超过70%。抽出物中未发现三不饱和脂肪酸。     

Enzymatic Synthesis of l‐Ascorbyl Fatty Acid Esters Under Ultrasonic Irradiation and Comparison of Their Antioxidant Activity and Stability

A series of novel l ‐ascorbyl fatty acid esters were synthesized by catalization of Novozym^® 435 under ultrasonic irradiation and characterized by infrared spectroscopy, electrospray ionization mass spectra, and nuclear magnetic resonance. Their properties especially antioxidant activity and stability were investigated. The results showed that the reducing power, the scavenging activity of hydroxyl radical and 2,2‐diphenyl‐1‐picrylhydrazyl radical were decreased with the increase of the number of carbon atoms in fatty acid. The hydroxyl radical scavenging activity and reducing power of l ‐ascorbyl saturated fatty acid esters were better than that of tert‐butylhydroquinone. The induction period in lipid oxidation of l ‐ascorbyl saturated fatty acid esters and tert‐butylhydroquinone were longer than that of l ‐ascorbyl unsaturated fatty acid esters and l ‐ascorbic acid both in soybean oil and lard. Besides, the l ‐ascorbyl fatty acid esters showed different stabilities in different conditions by comparing with l ‐ascorbic acid, and the l ‐ascorbyl saturated fatty acid esters were more stable than l ‐ascorbyl unsaturated fatty acid esters in ethanol solution.