蛋黄卵磷脂中两种溶血磷脂的分离与结构鉴定

通过柱层析分离法对蛋黄卵磷脂中的两种溶血磷脂(溶血磷脂酰胆碱和溶血磷脂酰乙醇胺)进行分离纯化,并采用ESI质谱、核磁共振氢谱和碳谱、气相色谱对其进行结构鉴定。结果表明:蛋黄来源的溶血磷脂酰胆碱主要由1-棕榈酰溶血磷脂酰胆碱,1-亚油酰溶血磷脂酰胆碱,1-硬脂酰溶血磷脂酰胆碱,1-油酰溶血磷脂酰胆碱4种化合物组成;溶血磷脂酰乙醇胺主要由1-棕榈酰溶血磷脂酰乙醇胺,1-硬脂酰溶血磷脂酰乙醇胺,1-油酰溶血磷脂酰乙醇胺3种化合物组成。     

以酶催化氧化油脂的方法制备香味料的研究进展

脂肪氧合酶催化油脂中的不饱和脂肪酸生成氢过氧化物,氢过氧化物再在裂解酶的作用下,生成具有青草香、青叶香香气特征的挥发性醛类物质。主要论述了不饱和脂肪酸酶催化氧化的基本途径,脂肪氧合酶的制备及氢过氧化物的生成,裂解酶的制备及氢过氧化物的裂解过程。并介绍了酶催化氧化油脂生成香味料的现状,展望了其发展前景。     

鸡蛋高温贮藏下脂质变化及酶活相关性研究

本研究通过考察鸡蛋高温贮藏(37℃)条件下脂质组分变化、脂肪酶活性变化及氧化指标的变化,并借助相关性分析阐释酶活变化与脂质氧化的内在联系。实验结果表明:贮藏过程中鸡蛋失重率、蛋黄p H、蛋黄水分含量显著增加而蛋黄指数和哈弗单位(HU)显著下降(p0.05);37℃贮藏15 d后,总脂质含量由于水分迁移而呈现下降趋势(从28.93 g/100 g降至24.20 g/100 g),磷脂含量显著降低(45.55 g/100 g降至34.37 g/100 g脂质)而游离脂肪酸显著增加(1.24 g/100 g增至3.67 g/100 g脂质),与脂质变化相关的中性脂肪酶、酸性脂肪酶及磷脂酶至贮藏结束活力分别下降76.50%、56.78%、56.81%。磷脂组分中的磷脂酰胆碱(Phosphatidylcholine,PC)、磷脂酰乙醇胺(Phosphatidyl ethanolamine,PE)、磷脂酰肌醇(Phosphatidylinositol,PI)在贮藏过程中也呈现含量显著下降的趋势而过氧化值(Peroxide value,POV)、硫代巴比妥酸值(Thiobarbituric Acid Reactive Substances,TBARS)呈现显著升高。相关性分析证明脂质组分变化与酶活变化显著相关。本研究说明鸡蛋贮藏中脂质会发生明显的水解及氧化,这些变化在一定程度上由酶促氧化造成。     

无豆腥味大豆的筛选、培育和利用前景

大豆豆腥味严重影响大豆制品的口感、风味和营养价值,选育无豆腥味大豆是克服大豆豆腥味的重要途径之一。 一、豆腥味产生的原因及无腥味大豆的 营养优势 大豆蛋白制品产生豆腥味是油脂中不饱和脂肪酸促氧化反应的结果,其中的关键酶是脂肪氧合酶（Lipoxygenase,简称Lox）,脂肪氧合酶催化不饱和脂肪酸中双顺式1,4- 戊二烯结构,通过加氧反应,形成氢过氧化物,进而分解形成小分子的醛、醇等挥发性物质,产生豆腥味和苦涩味。并且脂肪氧合酶产生的脂肪酸氢过氧化物能直接与食品中的蛋白质和氨基酸结合,降低食品食用性和营养价值。     

几种水产动植物组织中脂肪氧合酶反应产物的液相色谱分析

目的分析几种水产动植物组织中脂肪氧合酶反应产物,了解不同来源LOX的产物特异性.方法采用正相液相色谱,用Inertsil SIL-100A色谱柱(4.6mm×150mm,5 μm),正己烷-异丙醇(两者体积比991)为流动相,紫外检测波长为235 nm.结果浒苔LOX-1#催化亚油酸甲酯氧化主要形成9-氢过氧化物,而LOX-2#催化亚油酸甲酯氧化形成9-氢过氧化物及13-氢过氧化物,二者比例为2476;在pH 4.0时罗非鱼鳃组织LOX几乎生成等量的9-氢过氧化物和13-氢过氧化物,而在pH10.0时生成的产物主要为9-氢过氧化物;南美白对虾血淋巴LOX生成的产物为13-氢过氧化物.结论LOX产物的特异性与酶的来源及其反应条件有关.     

液相31P-NMR快速检测鱼子酱中磷脂

建立液相31P-核磁共振光谱法快速检测鱼子酱食品中磷脂的分析方法。样品匀浆后氯仿和甲醇混合溶剂提取其中的全脂,无需分离直接溶于氘代试剂后进行核磁分析。该方法回收率为96%～102%,相对标准偏差不超过5%。采用本方法对4 种品牌鱼子酱食品检测均发现6 种磷脂组分存在,且圆鳍鱼籽中磷脂酰胆碱和溶血磷脂酰胆碱总量均占总磷脂量的80%以上,而鲟鱼籽中磷脂酰肌醇含量远高于圆鳍鱼籽。其他3 种磷脂磷脂酰乙醇胺、鞘磷脂和甘油磷脂酸在2 种取材的鱼子酱中含量相差不多。     

核磁共振氢谱法分析食用油氧化产物

高场核磁共振近年来已应用到油脂品质检测领域。通过高温加热实验加速油脂劣变,制备不同氧化程度大豆油样品,利用高场核磁共振仪采集样品的氢谱数据,积分氢谱各指纹峰,计算各时间点油脂氧化产物的相对含量。结果表明:所有氧化产物与自由基链式反应机理的引发和传递阶段相符合;氧化全程顺式环氧化物含量高于反式,仲醇含量于伯醇,醛类物质中反-2-烯醛含量最高,加热6 h后其含量高达17. 94 mmol/mol。高场核磁共振氢谱技术在食用油品质快速检测领域具备潜在应用价值。     

磷脂酰乙醇胺-还原糖美拉德产物的制备及抗氧化活性研究

为研究亚麻籽炒籽过程中形成的美拉德产物(MRPs)以及提高低温压榨亚麻籽油的氧化稳定性,将3种还原糖(葡萄糖、果糖和木糖)与磷脂酰乙醇胺(PE)进行模拟反应,探究反应温度、反应时间和底物物质的量比对MRPs抗氧化活性的影响,利用质谱分析MRPs的主要成分,并考察MRPs对低温压榨亚麻籽油氧化稳定性和醛类化合物形成的影响。结果表明：PE-木糖体系的MRPs具有最高的体外抗氧化能力,其最适反应条件为PE与木糖物质的量比1∶1、反应温度160℃、反应时间60 min,在该条件下MRPs (2 mg/mL)DPPH自由基清除率达79.57%,铁离子还原抗氧化能力(FRAP)为43.65μmol/g,铁离子螯合能力为13.34%;通过质谱分析发现由一分子木糖和一分子PE反应形成的PE-吡咯-2-甲醛为MRPs中的主要成分;在190℃加速氧化实验中,PE-木糖体系的MRPs对低温压榨亚麻籽油过氧化值和p-茴香胺值的增长表现出与TBHQ相似的抑制作用,同时核磁共振氢谱分析结果表明MRPs可以减缓单烯醛和二烯醛的生成。综上,MRPs可以有效提高油脂的氧化稳定性。     

豆浆模拟体系中挥发性风味物质的比较研究

选择大豆蛋白、大豆甘油三酯、大豆脂肪氧合酶和胰脂肪酶4种主要组分,按照实际豆浆的组分含量和酶活大小进行混合制备豆浆模拟体系。分别利用二甲基酚橙法和顶空固相微萃取-气质联用法测定体系中脂质氢过氧化物和挥发性风味物质。结果表明:脂肪氧合酶催化甘油三酯氧化生成的脂质氢过氧化物相当于3. 958 mmol/L H2O2,生成的挥发性风味物质总量为43. 80 mg/kg;而脂肪氧合酶催化甘油三酯水解产物生成的脂质氢过氧化物相当于52. 243 mmol/L H2O2,生成的挥发性风味物质总量为668. 42 mg/kg。同时在该反应条件下对模拟体系和豆浆产生的挥发性风味物质进行主成分分析,模拟体系和3个豆浆样品集中在得分图相近区域,结果判定豆浆模拟体系产生的风味与真实豆浆的特征风味具有较好的相似性。     

脂肪氧合酶诱导脂质氧化与大豆制品品质的关系

大豆因其价廉、营养价值高而广泛应用于食品加工中。然而,普通大豆种子含有脂肪氧合酶,该酶催化多不饱和脂肪酸氧化产生氢过氧化物及其降解产物,作为潜在的反应物质它们可引起大豆蛋白质和氨基酸等的劣变,从而影响豆制品的品质。本文综述了氧化脂质与蛋白质和氨基酸的相互作用,以及脂肪氧合酶诱导脂质氧化与大豆制品品质的关系。简要回顾了通过控制脂肪氧合酶的活性,实现大豆制品品质及风味改善方面的最新进展。     

NMR和GC-MS研究加热对奶油主要成分及香气化合物的影响

为深入了解加热过程中奶油主要成分和香气成分的变化机理，对加热前后奶油进行分析。利用核磁共振（nuclear magnetic resonance，NMR）技术分别对奶油中的极性组分和非极性组分进行定量分析，同时利用气相色谱-质谱（gas chromatography-mass spectrometry，GC-MS）联用技术对加热前后奶油中的关键香气化合物进行鉴定。NMR分析表明，奶油中的极性组分主要为乳糖以及少量的游离氨基酸、游离脂肪酸和有机酸，非极性组分主要为甘油三酯以及少量的双甘酯和单甘酯。经加热后，极性组分含量大量减少，主要为乳糖和游离氨基酸，而非极性组分含量减少相对较小；GC-MS分析表明，短链脂肪酸和醛类含量增加相对较少，甲基酮、内酯和美拉德反应产物含量增加显著，其中甲硫基丙醛、麦芽酚和呋喃酮仅在加热后奶油中检出。结果表明加热过程中美拉德反应产物的形成和脂质来源化合物的增加分别造成了奶油中极性组分和脂肪酸的减少。该研究结果为奶油风味及产品研究提供了思路。     

Natural lecithins and phosphorylated acylglycerols as inhibitors of autoxidation of fats and oils

Both natural phospholipids (soybean or rapeseed lecithin) and phosphorylated acylglycerols (produced by treatment of diacylglycerols with phosphorus pentoxide or metaphosphoric acid) inhibit the oxidation of polyunsaturated fatty acid esters in rapeseed, sunflower seed or soybean oils, but only higher phospholipid additions (more than 0.2%) have pronounced effect on the stability under storage conditions. Partially hydrogenated oils are stabilized similarly as original liquid oils. The inhibitory activity of synthetic phospholipids is particularly high in presence of trace metal compounds, such as copper, iron or manganese. The chelating activity is nearly the same in the case of phosphatidic acids, their ammonium salts, phosphatidylcholine or phosphatidylethanolamine. The hydroperoxide decomposing activity is, however, much higher in nitrogen-containing phospholipids than in the corresponding phosphatidic acids. The content of oxidized fatty acids is lower in phospholipids than in triacylglycerols.     

Determination of Omega Fatty Acid Profiles in Egg Yolk by HILIC-LC-MS and GC-MS

The paper presents the analysis of the profile composition of fatty acids in the molecules of phosphatidylcholine and phosphatidylethanolamine, by using hydrophilic interaction liquid chromatography and gas chromatography coupled with mass spectrometry. The profiles of 15 phosphatidylcholine and 8 phosphatidylethanolamine species were analyzed with a newly developed hydrophilic interaction liquid chromatography (HILIC)–electrospray ionization (ESI)–tandem mass spectroscopy (MS/MS) method, by using a new stationary bonded phase. The application of the new method in control and experimental groups of egg yolk revealed significant differences in the composition of phospholipid species containing mainly polyunsaturated fatty acids. Additionally, using GC-MS, the profile of fatty acids in four groups with different dietary supplementation of hens was analyzed and 20 fatty acids in egg yolks were determined. Monounsaturated fatty acids were found in higher amounts than saturated fatty acids and polyunsaturated fatty acids in egg yolks. Oleic acid (18:1) was the major monounsaturated fatty acid in egg yolk while palmitic acid (16:0) was the major saturated fatty acid. Linoleic acid (18:2), arachidonic acid (20:4), and docosahexaenoic acid (22:6) reached the highest levels among the polyunsaturated fatty acids.     

Effect of phospholipids on membrane characteristics and storage stability of liposomes

The membrane characteristics and storage stability of liposomes prepared by different phospholipids were investigated, including soybean phosphatidylcholine (SPC), egg yolk phosphatidylcholine (EPC) and hydrogenated soy phosphatidylcholine (HSPC). The mean vesicle size of HSPC liposomes was 437.8 nm, while the size of SPC and EPC liposomes were 112.3 and 121.3 nm, respectively. The AFM and TEM images demonstrated that SPC and EPC liposomes exhibited a more uniform distribution and greater membrane fluidity. The liposomes demonstrated different crystallization behavior and phase transition temperatures by XRD and DSC, respectively. Due to high saturated fatty acids content of HSPC, these liposomes displayed a tighter membrane packing as evident by FTIR and Raman spectra. The membrane hydrophobicity and micropolarity decreased with storage time. During storage, HSPC liposomes maintained a more compact membrane structure. HSPC liposomes were the most stable during storage as evident by significantly lower levels of lipid hydrolysis and oxidation.     

Oxidative stability of oil from blubber of harp seal (Phoca groenlandica) as assessed by NMR and standard procedures

Oils from seal blubber and cod liver were extracted, refined and bleached in a laboratory scale process. Oxidative stability of oils was evaluated over a 16-day period under accelerated oxidation conditions at 65°C. Peroxide value (PV), contents of conjugated dienes (CD) and trienes (CT), 2-thiobarbituric acid reactive substances (TBARS) and p-anisidine values (AnV) were determined. In addition, NMR spectroscopy was used to monitor relative changes in the proton pattern of the fatty acids of oils during storage. Cod liver oil showed higher PV, CD, CT and TBARS values as compared with seal blubber oil. The ratio of aliphatic to olefinic protons in both oils determined by NMR spectroscopy increased steadily over the entire length of the storage period, indicating progressive oxidation of unsaturated fatty acids in both oils. A significant correlation (P ≤0·05) was found between these ratios and TOTOX values (2PV + AnV) for both oils, thus suggesting that NMR methodology can be used as an effective means to simultaneously estimate both primary and secondary oxidation changes.     

黄喉拟水龟蛋营养成分分析及评价

对黄喉拟水龟蛋的蛋白质、氨基酸、矿物质、蛋黄中磷脂及脂肪酸组成等营养成分及价值进行评价。结果表明:与鸡蛋的营养组成相比,黄喉拟水龟蛋蛋清蛋白质种类多于鸡蛋蛋清,氨基酸组成符合理想模式,铁、镁、锌、磷含量高。龟蛋黄脂肪含量低于鸡蛋蛋黄,脂肪酸种类多,不饱和脂肪酸占总脂肪酸的80.72%,多不饱和脂肪酸二十二碳六稀酸(docosahexaenoic acid,DHA)6.39%,花生四稀酸3.72%,二十碳五稀酸(eicosapentaenoic acid,EPA)3.69%。龟蛋蛋白质种类丰富,矿物质和不饱和脂肪酸含量高,是一种高价值优质健康食品。     

微波烹调方式对乌鸡蛋黄脂质变化规律的影响

本文选取乌鸡蛋黄作为试验对象,通过调整微波炉不同加热模式和加热时间,分析了微波烹调方式对乌鸡蛋黄脂质影响,研究其相关变化规律。研究结果表明,在高火、高中火和中火三种加热模式不同加热时间条件下,乌鸡蛋黄中总脂质含量呈现先增加后降低的变化规律;甘油三酯(TG)和游离脂肪酸等主要脂质成分的含量呈升高趋势,而磷脂(PL)含量则呈先升高后降低的变化规律;磷脂组分中的磷脂酰胆碱(PC)、磷脂酰乙醇胺(PE)、磷脂酸(PA)、磷脂酰己醇(PI)、磷脂酰丝氨酸(PS)、溶血卵磷脂(LPC)、磷脂酰甘油(PG)和溶血磷脂酰乙醇胺(LPE)的峰面积变化规律基本一致,均呈现先高后低的变化特征。在不同加热场景下,乌鸡蛋黄脂肪酸C16:0、C18:0、C20:0、C24:0和SFA等组分变化规律基本一致。其中,乌鸡蛋黄脂肪酸组分C16:0、C20:0和SFA的含量变化总体呈上升趋势,增幅分别为2.2%、14.77%和17.65%,乌鸡蛋黄脂肪酸组分C18:0、C24:0含量变化总体呈先升后降的特征,C18:0较对照样本先增加至90.16%,后降低为66.80%,C24:0较对照样本先增加至27.61%,后降低为27.33%。在高火、高中火和中火三个保温点下,乌鸡蛋黄脂质营养成分保留率相差范围约为5%～10%。通过本文相关内容的分析研究,以科学合理地使用微波炉加热食品,尽可能多地保留乌鸡蛋营养物质。     

Fatty acid composition of certified organic,conventional and omega-3 eggs

The objective of this study was to compare the fatty acid composition of commercially available conventional, certified organic, and omega-3 eggs. Egg components were assessed, and the fatty acid composition of yolk lipids was determined by gas chromatography. Organic egg yolk contained a higher percentage of palmitic and stearic acids than did conventional yolk (P < 0.05) with no differences observed in the monounsaturated or polyunsaturated fatty acid compositions. Compared with organic and conventional eggs, omega-3 egg yolk contained lower percentages of myristic and palmitic acids, and higher omega-3 fatty acids. In a sub-analysis of conventional egg types, the percent of stearic acid in “cage” egg yolk was significantly lower (P < 0.05) than those of “barn-laid” and “free-range” eggs. “Cage” eggs had a significantly lower percentage (P < 0.05) of arachidonic acid than had “barn-laid” eggs. Consumption of omega-3 eggs has the potential to confer health benefits through the increase in intake of omega-3 fatty acids. With regard to organic or conventional methods of production, the small differences in saturated fatty acids observed in the present study are unlikely to have any significant metabolic effect on the consumer.     

Lipid Oxidation. Part 3. Oxidation of Egg Phosphatidylethanolamine

Phosphatidylamine isolated from egg yolk phospholipids was autoxidized at 60 °C. Oxidation products were separated by thin layer chromatography on silica gel and by column chromatography on DEAE-cellulose. The fractions were characterized by UV and IR spectra and by chemical analysis. Polyunsaturated fatty acids were destroyed during the oxidation, the content of primary amino groups decreased and imine derivatives appeared.