Effect of Lipid-Protein Interactions on Hydration Characteristics of Defatted Offal Protein Isolates

Water-protein interactions of rumen and lung protein isolates defatted by different solvents were studied by means of water sorption isotherms. Two isolation procedures were employed to obtain the isolates: (1) alkaline solubilization and isoelectric precipitation of proteins; and (2) SDS solubilization and FeCl₃ precipitation of proteins. Water monolayer values of the protein fraction showed a marked dependence on the dielectric constant of the solvent used for lipid extraction. In lung isolates they increased up to a peak when solvents of intermediate polarity were employed whereas in rumen isolates they were initially constant, decreasing with increase of polarity of solvent. Affinity of water to protein support, showed a more complex pattern and was dramatically affected by the isolation procedure used.     

Lipid Composition and Hydration Characteristics of Lung Protein Isolates Defatted by Several Solvents

Different portions of a protein isolate from bovine lungs were exhaustively defatted by solvents of varying polarities. Phospholipids, cholesterol and cholesterol esters, free fatty acids, mono-, di- and triacylglycerols were quantitatively determined in the extracts. Their amount was dependant on the polarity of the solvent employed. Neutral lipids were quantitatively removed by all solvents whereas the amount of phospholipids extracted increased with solvent polarity. The water monolayer capacity of the defatted protein (obtained by the BET equation) showed an increase up to the maximum with the increase of the residual lipid content (determined by Folch wash). The results indicated that more protein polar sites were exposed when the lipid fraction (mainly phospholipids) was present.     

Hydrophobic and Electrostatic Interactions on Extrusion of Protein Isolates

Lung protein isolates previously defatted by solvents of increasing polarity were extruded. Water monolayer values of these isolates, calculated from water vapor isotherms, showed a maximum when solvents of intermediate polarity were used. Shear resistance of the extruded products presented a similar behavior, with maximum values attained when the same solvents were employed to defat the isolates prior to extrusion. Phospholipid percentage in lipid fraction of the solvent extracts showed that minimum phospholipids were removed from the isolates when these solvents were used. The results suggested that the presence of phospholipid in the isolates after defatting could be important in improving the extrusion of these systems. Hydrophobic and electrostatic interactions between the macromolecules involved seemed therefore, to be relevant for the final texture obtained by extrusion.     

两种大豆分离蛋白的比较研究

本文以醇洗豆粕为原料制备大豆分离蛋白(SPI-A),并将之与传统的碱溶酸沉工艺制备的大豆分离蛋白(SPI-C)作比较,发现脱脂豆粕经醇洗之后所制备的大豆分离蛋白,其功能性质明显优于传统的大豆分离蛋白。凝胶性能研究表明样品SPI-A的凝胶强度是385.4g,明显高于样品CSPI(85.4g);样品SPI-A的乳化和起泡性能也有明显的改善;HPLC研究表明SPI-A和SPI-C两种样品几乎在同一时间出峰,但激光光散射分析表明样品SPI-A的流体动力学半径远比样品SPI-C的大,说明样品SPI-A形成的聚集体体积较大,结构较为疏松,而样品SPI-C所形成的聚集体体积较小且结构较为致密。     

蛋白质氧化对乳清分离蛋白功能性质的影响

为了进一步研究蛋白质氧化对乳清分离蛋白(WPI)功能性质及流变学性质的影响,试验采用两种不同浓度的氧化系统H2O2(1 mmoL/L~20 mmoL/L)和FeCl3浓度(0.1 mmoL/L~2 mmoL/L)对WPI分别氧化1 h、3 h、5 h,测定其性质。结果表明:20 mmoL/L的H2O2氧化WPI 5 h,其乳化活性下降了50%以上;1 mmoL/L FeCl3氧化WPI 3 h,其凝胶硬度降低了94.5%;20 mmoL/L H2O2与1mmoL/L FeCl3氧化WPI 3 h,其弹性从0.976下降到0.713和0.721,分别降低了26.9%和26.1%;当H2O2浓度20 mmoL/L时,弹性模量从8154 Pa降到5399 Pa,复合模量从10890 Pa降到6653 Pa,分别降低了33.79%和38.91%;当FeCl3浓度为1 mmoL/L时,弹性模量从8154 Pa降到4935 Pa,复合模量从10890 Pa降到6049 Pa,分别降低了39.47%和44.45%。长时间高浓度的氧化条件使得蛋白质的空间结构受到严重影响,WPI的功能性质及凝胶质地发生较大的变化。因此,在实际生产中应尽可能地控制蛋白氧化的发生,减少其因为氧化所带来的营养损失或者降低其应用价值。     

大米分离蛋白的酶法提取及其性质

本文研究了以糖渣为原料,用淀粉酶法水解法制备大米分离蛋白(E-RPI)的反应条件,并测定了蛋白质的溶解性、乳化性及其氨基酸组成。结果表明,反应中固液比为1:12.96、加酶量为0.096％、反应时间为2.3h时效果最好,使糖溶出量达到原料重量的25.7％,产物中的蛋白含量为88.6％,回收率为90.5％;E-RPI的乳化活性随pH值的升高而增大,与大豆蛋白相比,乳化活性低而稳定性高。E-RPI中除赖氨酸外,其它必需氨基酸的含量均高于大豆蛋白和酪蛋白。     

脂肪氧化对蛋白质结构的影响

为了探索脂肪氧化对蛋白质结构的影响,利用不同条件下制备的氧化脂肪,加入蛋白后在同样条件下作用一定时间,测定蛋白质的各项指标。结果表明：加入蛋白后硫代巴比妥酸值(TBA)值下降,蛋白氧化值升高(羰基含量),表面疏水性增加且最大发射波长(λmax)发生红移,二级结构变化明显。说明脂肪氧化对蛋白质结构产生了影响。     

Cholesterol and Other Lipid Extraction from Egg Yolk Using Organic Solvents: Effects on Functional Properties of Yolk

Cholesterol extraction from dehydrated egg yolk, using petroleum ether or petroleum ether-ethanol (35:65) resulted in decreased cholesterol content with petroleum ether and almost complete removal with petroleum ether-ethanol. Yolk extracted with petroleum ether gave emulsions of similar rates of coalescence to those prepared with dried yolk and mayonnaise-like emulsions of higher Theological properties. Yolk extracted with petroleum ether-ethanol gave emulsions of lower stability and did not lead to preparation of mayonnaise-like emulsions. Both yolk protein concentrates showed better foaming activity and foam stabilizing ability than dried yolk.     

低温冷冻条件对大豆分离蛋白功能性的影响

通过大豆分离蛋白（soybean protein isolate,SPI）冷冻前后功能性的变化,研究低温冷冻条件（料液比、冷冻温度、冷冻时间）对SPI功能性（保水保油性、乳化特性及质构特性）的影响。结果表明：在经过冷冻实验的样品中,随着SPI添加量的减小,其保水保油性、乳化性先增加后减小,当SPI料液比为1∶12时,其保水性、保油性、乳化稳定性、硬度和弹性均达到相对最大;冷冻温度为－18 ℃时,其保水保油性、乳化性、硬度和弹性相对最大,－20 ℃时,其乳化稳定性相对最好;随着冷冻时间延长,其乳化稳定性减小,冷冻3 d时,SPI的乳化稳定性相对最好,冷冻2 d时其保水性相对最大。和未经冷冻处理的原样品相比,经过冷冻处理的SPI,功能性明显减弱,其中保水保油性、乳化性、质构特性都小于未冷冻处理的SPI。     

中式香肠中脂肪氧化对蛋白质氧化的影响

以中式香肠为研究对象,通过对加工、储藏过程中包装、温度、光照以及抗氧化剂的不同处理,建立中式香肠的脂肪氧化模型,结合对其蛋白质氧化的跟踪检测,分析了中式香肠中脂肪氧化与蛋白质氧化之间的相关性。结果表明:对于脂肪氧化的抑制作用,有效抑制了蛋白质氧化形成羰基类物质,且与脂肪氧化初级和次级产物均表现较好的相关性;脂肪氧化对于蛋白质游离硫醇基流失的促进作用是由脂肪氧化次级产物挥发性醛类物质引起的。     

不同溶剂对香芋蛋白提取及活性的影响

对张溪香芋的水提物、盐提物、醇提物、Tris提取物、等电点沉淀物的蛋白质、氨基酸组成、总糖含量、总酚含量和包括抗氧化活性、凝血活性及胰蛋白酶抑制活性进行分析,以获得香芋蛋白活性较高的提取物。抗氧化性实验表明,各提取物具有一定的ABTS清除能力和羟基自由基清除能力,其中Tris提取物的ABTS清除能力(IC50=3.78 mg/m L)和羟基自由基清除能力均较高。香芋提取物均对羊血红细胞没有凝血活性,但均对兔血红细胞具有凝集活性,特异性凝集活力大小为盐提物(3.24×103 HU/mg)Tris提取物(2.88×103 HU/mg)等电点沉淀物(1.86×103 HU/mg)水提物(1.41×103 HU/mg)醇提物(0.98×103 HU/mg);五种提取物中,乙醇提取物没有胰蛋白酶抑制活性,盐提物、水提物、Tris提取物胰蛋白酶抑制活性较高,分别为134 TIU/mg、130.51 TIU/mg、113.30 TIU/mg。结果表明,Tris提取物含有较多具有高活性的蛋白质,且蛋白条带较最全。     

酶法改性对鹰嘴豆分离蛋白功能性的影响

研究了Alcalase及转谷氨酰胺酶(TGase)酶法改性对鹰嘴豆分离蛋白(CPI)的溶解性及乳化性的影响。CPI经A1calase水解60min(DH5.91%),低离子强度对溶解性不再有负面影响;CPI水解30min(DH5.80%),无盐或0.1mol/L NaCl条件下,蛋白质的乳化活力分别是未改性前的1.22和2.78倍。TGase对CPI在0.1mol/L NaCl条件下的溶解性及乳化活力不能起到良好的改善作用。     

高压均质对大豆分离蛋白功能特性的影响

研究了高压均质压力(40～160MPa)和均质次数(1次/2次)对大豆分离蛋白(SPI)功能特性的影响。结果表明:均质次数为1次时,40MPa和80MPa可显著提高SPI的溶解性,压力增加至120MPa和160MPa时,溶解性反而明显下降,但持水性提高;1次均质可以显著改善SPI乳化活性,而对其乳化稳定性影响不大;80MPa1次均质和160MPa2次均质能显著提高SPI凝胶性;除160MPa外,均质压力相同时,1次均质比2次均质更有利于改善SPI功能特性(包括溶解性、乳化性、凝胶性和持油性)。     

蛋白及脂肪含量对腐竹差异成膜的影响

腐竹是我国历史悠久的传统的大豆制品之一。本文以提升腐竹产量、改善其机械性能及提升其营养价值为目标,使用大豆分离蛋白及大豆油为原料,采用人工模拟豆浆体系进行成膜实验,研究蛋白含量、脂肪含量、蛋白变性程度及蛋白组分对腐竹成膜的影响。结果表明:脂质含量的提高能提升成膜速度、增加膜弹性、提高成膜的蛋白和脂肪含量,但是脂质的含量过高又会对以上指标产生一定的抑制作用。随着蛋白添加量的增加,成膜速度会随之加快、膜的硬度增大、膜的蛋白含量增高、膜的脂质含量先增后减。蛋白变性程度提高能提升成膜速度,改善膜的机械性能和营养价值。尽管蛋白组分的改变对成膜速度影响不大,但是11S/7S直接影响膜的机械性能,11S/7S越高,膜的机械性能越优秀。     

菜籽饼粕蛋白的提取、功能特性及其在食品中应用的研究进展

菜籽饼粕作为油菜籽榨油后的副产物,其蛋白质含量丰富、氨基酸组成均衡,是一种优质的植物蛋白资源,但长期以来主要用于饲料行业,经济效益较低.从菜籽饼粕中提取的菜籽蛋白已被证明具有良好的乳化性、凝胶性等功能特性及降血压、抗氧化等生理活性.目前,菜籽蛋白已被欧盟及FDA批准作为新食品原料,可作为人类食用的优质植物蛋白资源.本文...     

冷榨南瓜子油饼蛋白质提取工艺及功能性质研究

以冷榨南瓜子饼粕为原料,采用碱溶酸沉法提取其中的蛋白质,分析pH值、料液比、提取温度、提取时间等单因素对提取率的影响,用响应曲面法优化工艺条件,得到冷榨南瓜子油饼蛋白质提取最佳工艺:料液比1:12(g/mL)、提取温度50℃、提取时间22.5min。在此工艺条件下,饼中蛋白质粉的平均提取率为23.92%,蛋白质质量分数86.48%(湿基,蛋白粉水分质量分数为9.31%)。对提取出的蛋白粉进行各种理化及功能性分析,结果表明:提取的冷榨南瓜子蛋白粉具有良好的加工性能,特别是持水能力和持油能力,均高于大豆分离蛋白。且随着蛋白溶液浓度和加热时间的变化,其持水及持油力的变化极显著;乳化性随着蛋白质溶液浓度的升高而升高,而乳化稳定性在蛋白质质量分数5%时出现明显下降,两者数值均随蛋白质溶液质量分数的变化有极显著差异,但整体也随蛋白质质量分数的升高而升高;起泡性随蛋白质质量分数升高而增大,泡沫稳定性几乎不随蛋白质质量分数变化。     

加工条件对大豆分离蛋白塑料特性的影响

研究了在大豆分离蛋白塑料的热压过程中,成型时间、温度、压力和增塑剂的添加量对其透光率、拉伸强度、伸长率和吸水率的影响,得到了热压形成大豆分离蛋白塑料的最佳工艺条件。     

Partial Lipid Extraction of Egg Yolk Powder: Effects on Emulsifying Properties and Soluble Protein Fraction

Egg yolk powder was partly defatted using hexane, 95% ethanol, isopropanol, chloroform-methanol (2:1, v:v) hexane-isopropanol (77:23, w:w) and hexane-ethanol (77:23, w:w). Hexane-isopropanol was most efficient, extracting more than 50% of the lipid. Protein solubility and emulsifying activity of the extracted powder decreased after extraction. Hexane-isopropanol reduced emulsifying activity about 14% and protein solubility to 13.8% from 15.7%. Extraction with other solvents resulted in up to 41% loss of emulsifying activity; protein solubility decreased to as low as 3%. Ovalbumin in the water-soluble fraction of extracted egg yolk powder reduced its emulsifying effectiveness.     

金枪鱼制品中几种DNA提取方法的效果比较

金枪鱼种类繁多,市场上以次充好、以假乱真的现象时有发生.基于DNA的检测技术已经被广泛用于金枪鱼制品品种掺假检测.而DNA提取对DNA检测技术的运用至关重要.本研究以28份深加工金枪鱼产品为样本,采用3种DNA提取方法(SDS法以及2种市售试剂盒)进行DNA提取,并对DNA的质量、得率、PCR扩增及方法的可操作性等方面...     

增塑剂对大豆蛋白可食膜特性的影响

研究了增塑剂对大豆分离蛋白膜(热法成膜和酶法成膜)成膜特性的影响。增塑剂的种类(甘油、山梨醇或甘油山梨醇的等量混合物)对大豆分离蛋白膜的性能有明显影响。无论是否添加谷氨酰胺转移酶(TGase)，以山梨醇为增塑剂的膜都具有最高的抗拉强度、表面疏水性和总可溶性物量，最低的断裂伸长率、水分含量和透光率。TGase处理SPI(4U／g．蛋白)，可显著改善蛋白膜的抗拉强度和表面疏水性，抗拉强度和表面疏水性分别比对照膜增加10％～20％和17％～56％(P≤0.05)；同时也明显降低了(P≤0.05)膜的断裂伸长率、水分含量、总可溶性物量及透光率。