酪蛋白酸钠膜的DSC分析

采用差示扫描量热法(DSC)分析,研究不同相对湿度(RH)条件下,酪蛋白酸钠(NaCas)膜的热特性以及谷氨酰胺转移酶(TGase)改性对热特性的影响.对于NaCas膜,无论是对照膜还是TGase改性膜,蛋白膜的热稳定性随着RH的增高而下降.TGase改性改变了NaCas膜吸热峰出现的位置与数量.在同一RH时,TGase改性膜更易失去水分.TGase改性使NaCas膜的耐热特性发生了明显改变,可能是TGase作用改变了NaCas的不同组分的耐热特性所致.     

酪蛋白酸钠膜的水分吸附特性

作者以大豆蛋白酪蛋白酸钠(NaCas)膜为对象,从吸附动力学和水分吸附等温线研究了蛋白膜的水分吸附特性.NaCas膜水分达到平衡所需要的时间受到所处相对湿度(RH)条件和增塑剂含量的影响.RH和增塑剂含量越低,达到平衡的时间越短;反之,则越长.TGase改性明显降低了蛋白膜的水分吸附速率及达到平衡的水分含量.NaCas膜水分吸附等温线数据能很好地与GAB模型吻合.     

大豆分离蛋白膜的DSC分析

采用差示扫描量热法(DSC),研究不同相对湿度(RH)条件下,大豆分离蛋白(SPI)膜的热特性以及谷氨酰胺转移酶(TGase)改性对热特性的影响。对于SPI膜,无论是对照膜还是TGase改性膜,蛋白膜的热稳定性随着RH的增高而下降。TGase改性改变了SPI膜吸热峰出现的位置与数量。在同一RH条件下,TGase改性膜更易失去水分。TGase改性使SPI膜的耐热特性基本未变。     

一些蛋白质和多肽对谷氨酰胺转胺酶热稳定性的影响

谷氨酰胺转胺酶(TGase)是一种催化蛋白质分子间产生共价交联的硫醇酶类,但其热稳定性较差,通过35～60℃之间的热处理研究,发现谷朊粉、大豆多肽、乳清蛋白、酪蛋白酸钠、乳清粉和脱脂乳6种蛋白和多肽物质对TGase酶活都表现出保护作用,其中酪蛋白酸钠和乳清蛋白较为显著。采用TG/DSC分析,我们获得了上述六种蛋白物质对TGase的相变温度(Tm),相变热焓(ΔH)和失重率(LW)影响的数据,其中酪蛋白酸钠对TGase的三种热力学参数改变最大,分别为32℃,40.5J/g和-7.0%。加入0.1%～2.0%的上述6种蛋白和多肽物质对TGase的冻干过程也具有保护作用,以0.5%的谷朊粉添加效果较好。     

EPA、DHA的微胶囊化:壁材的筛选

以产品的产率、效率和贮存稳定性 (包括产品的抗氧化性和心材的持留率 )为评定指标 ,选用多种蛋白质 ,如明胶 (GEL)、浓缩乳清蛋白 (WPC)、大豆分离蛋白 (SPI)、大豆水解蛋白 (SPH)和酪蛋白酸钠 (CAS)等 ,作为 EPA、DHA微胶囊化壁材 ,并进行了比较。结果表明 :SPI作为壁材制得的微胶囊产品具有较高的产率和效率 ,但其贮存稳定性很差 ;而 GEL、SPH(DH8)和 WPC 3种壁材制得的产品具有较好的贮存稳定性 ,其中又以 GEL为最佳。     

植物分离蛋白对卵巢切除大鼠血脂代谢的影响

目的:研究大米分离蛋白和大豆分离蛋白对因雌性激素缺乏引起的高胆固醇血症的影响.方法:将24只Wistar成年雌鼠随机分为4组.3组大鼠进行双侧卵巢切除手术,分别喂食添加20%酪蛋白(对照组)、大米分离蛋白或大豆分离蛋白的饲料.另1组进行卵巢伪切除手术,喂食添加20%酪蛋白的对照饲料,喂养4周后解剖,测定血清和肝脏中胆固醇、甘油三酯浓度以及粪中胆汁酸排泄量和蛋白表观消化率等指标.结果:卵巢切除明显增加成年雌鼠血清和肝脏中胆固醇和甘油三酯浓度.与酪蛋白组相比,饲料中添加大豆分离蛋白能显著降低卵巢切除大鼠血浆总胆固醇和低密度脂蛋白及胆固醇浓度(p＜0.05),但对血浆甘油三酯浓度无显著影响,同时明显降低肝重、肝脏中总脂、总胆固醇、游离胆固醇及甘油三酯总量,以及增加排粪量和胆汁酸排泄量,大豆分离蛋白表观消化率也明显比酪蛋白和大米分离蛋白高.大米分离蛋白对血脂没有明显降低效果,但肝脏总脂、总胆固醇、游离胆固醇和甘油三酯浓度明显低于酪蛋白饲料组,而排粪量、粪中胆汁酸排泄量和蛋白表观消化率则与酪蛋白组无显著差异.结论:抗消化蛋白对因雌性激素缺乏引起的高胆固醇血症有明显降低效果,可能的作用机制是由于该蛋白的低消化性干扰,肠道中胆汁酸代谢,增加粪中胆汁酸的排泄量来降低肝脏和血浆中胆固醇浓度.     

工艺条件对酶法改性大豆蛋白膜性能的影响Ⅱ

研究了底物蛋白的浓度、增塑剂的浓度、蛋白溶液预热处理的温度和时间及变性剂(2-巯基乙醇)处理等工艺参数对谷氨酰胺转移酶(TGase)改性大豆分离蛋白(SPI)膜性能的影响.SPI膜制好后裁切成所需要的样品形状,放在相对湿度为50%的环境中平衡48 h,测定抗拉强度(TS)、断裂伸长率(EB)、水分含量(MC)、总可溶性物质量(TSM)、表面疏水性(S0)及透光率等各项指标.随着底物蛋白质量浓度(3～9 g/dL)的增加,TGase改性SPI膜的TS值和EB值明显增加,而接触角和透光率明显下降.随着甘油含量增加,TGase改性SPI膜的TS值和接触角明显降低,透光率略有降低,而EB值和MC值明显增加.随着蛋白溶液预热处理温度(70～90 ℃)和时间(0.5～1.0 h)的增加,SPI膜的TS值明显增加,接触角和透光率稍有增加,TSM值略有下降.变性剂2-巯基乙醇(2-ME)的加入,使TGase改性SPI膜的TS值、接触角明显增加,MC值明显下降,TSM值和透光率变化不大.     

谷氨酰胺转氨酶改性可食性复合膜的研究

研究了以甘油为增塑剂时,谷氨酰胺转氨酶(TGase)对大豆分离蛋白(SPI)和谷朊粉(WG)复合膜功能特性的影响.应用综合评分法得出,当TGase的添加量为0.30%时,综合得分最高,为29.52,此时,复合膜的拉伸强度最大,为56.44 MPa.比对照提高了47.1%;撕裂强度最大,为206.61 N/mm,比对照提高了4.3%;膜的水分含量为12.90%,比对照降低了7.0%;膜的水蒸汽透过率为0.443 g·mm/(kPa·h·m2),比对照降低了12.7%.但添加TGase也使膜的透光率下降.     

湿法糖基化改性大豆分离蛋白在低致敏千页豆腐中的应用

为寻求高效的糖基化改性条件和良好的应用途径，本文以葡萄糖、木糖两种单糖为糖基供体，探究反应时间、反应温度、蛋白与糖比例、蛋白浓度对大豆分离蛋白湿法糖基化反应的影响，分析大豆分离蛋白-葡萄糖复合物(SPI-葡萄糖)、大豆分离蛋白-木糖复合物(SPI-木糖)致敏性的变化，并将SPI-葡萄糖、SPI-木糖应用于低致敏千页豆腐生产。结果表明，木糖相较于葡萄糖更易与大豆分离蛋白发生糖基化反应，但也更容易有类黑素产生。在蛋白浓度为25 mg/mL时，糖基化反应程度最高，并且糖基化反应程度与反应温度、反应时间、糖添加量呈正相关。SDS-PAGE和傅里叶变换红外光谱分析结果表明糖基化改性使大豆分离蛋白和糖分子发生了共价结合，SPI的自由氨基减少。糖基化反应程度越高，SPI致敏性越低，SPI-木糖接枝物致敏性降低程度最高可达50%，以其为原料经谷氨酰胺转氨酶(TG酶)交联所制作的千页豆腐有良好的弹性和咀嚼性。     

海藻酸钠对可食性复合膜性能的影响研究

在均匀实验设计方法得到乳清分离蛋白-酪蛋白酸钠复合蛋白膜的工艺参数的基础上,采用乳清分离蛋白、酪蛋白酸钠、海藻酸钠共混法制备可食性复合膜,研究海藻酸钠对复合膜的性能的影响。结果表明,适当浓度和比例的海藻酸钠能提高膜的机械性能和水溶性,但也降低了膜的透明度和阻隔性能。     

Functionality of microencapsulated high-fat powders in wheat bread

The objective of this project was to evaluate the performance of microencapsulated high-fat powders in bread in comparison to commercial partially hydrated vegetable fat. Breads with no added fat were used as a control. Powders with different encapsulating agents (caseinates or whey proteins), sugars (sucrose or lactose) and fat [milkfat (AMF, Anhydrous Milk Fat) or vegetable fat blend] were produced under various processing conditions. Specific volume, volume yield, bake loss, colour and crumb structure were all determined on the baked breads. Crumb compression tests, crumb texture profile analysis and crust penetration were used to evaluate the texture of the baked bread. Comparison of the results revealed that the effects the powders had on specific volume, volume yield, bake loss, crust colour and textural properties varied significantly. WPC75-2 (WPC, Whey Protein Concentrate, low homogenisation pressure, lactose) gave a similar specific volume to the commercial vegetable fat. Powders, which were produced with high homogenisation pressure, gave values of up to 20 % lower. WPC75-1 (WPC, high homogenisation pressure, sucrose) gave a compression value 10% higher than Std-1, (no added fat), while WPC75-1, NaCas-1 (NaCas, low homogenisation pressure, lactose) and NaCas-2 (NaCas, low homogenisation pressure, sucrose) performed as well as the commercial fat standard. Scanning electron microscopy showed differences in structure between the standard bread, bread with commercial vegetable fat and the breads containing WPC75-1 and WPC75-2.     

转谷氨酰胺酶对乳清浓缩蛋白-纳米微晶纤维素复合膜性能的影响

为了研究转谷氨酰胺酶(TG)对乳清浓缩蛋白(WPC)-纳米微晶纤维素(NCC)复合膜性能和结构的影响,本研究以WPC和NCC为原料,利用TG酶处理对WPC-NCC复合膜的机械性能和屏障性能进行优化,并探究TG酶的交联作用对乳清蛋白分子二级结构和复合膜成膜微观结构的作用情况。结果表明,在TG酶的添加量达到12 U/g_蛋白时,WPC-NCC复合膜的抗拉强度达到2.25 MPa,断裂伸长率达到86.75%,水蒸气透过率为4.40×10-12 gmPa-1s-1m-2,有效改善了WPC-NCC复合膜的机械性能性和水蒸气屏障性能。经过TG酶的处理,乳清蛋白结构向稳定有序的方向转变,减少了复合膜的孔洞数量和孔径,使成膜表面结构更加致密,促进了复合膜的机械性能和水蒸气屏障性能的提升。     

Physical properties of edible films made from mixtures of sodium caseinate and WPI

The physical properties of thin films (25–30 μm) made from mixtures of sodium caseinate (NaCas) and whey protein isolate (WPI) were investigated. Films were formed by mixing solutions of NaCas (2.5% w/w protein), plasticised with glycerol (NaCas–gly) at a glycerol:protein ratio of 0.32, with WPI solutions (2.3% w/w protein), plasticised (WPI-gly) at a glycerol:protein ratio 0.37. Tensile and water barrier properties of films formed from mixtures of NaCas–gly and WPI-gly were similar to films containing NaCas–gly only. Films containing only WPI-gly had higher maximum load and elastic modulus values than the mixed films. Increasing the NaCas–gly content of the films from 25 to 100% greatly increased solubility. This increased film solubility may increase the number of food applications for protein-based films.     

TG酶和羟丙基甲基纤维素改善乳清蛋白可食膜性能

以乳清浓缩蛋白(WPC)为基料,通过添加羟丙基甲基纤维素(HPMC,添加量为蛋白质量的5%~25%)和转谷氨酰胺酶(TG酶)对膜的性能进行改良,研究HPMC的添加量和转谷氨酰胺酶的交联作用对复合膜性能的影响。结果表明:HPMC能显著提高蛋白膜的抗拉强度,降低复合膜的断裂伸长率(p<0.05),TG酶能有效改善乳清蛋白-羟丙基甲基纤维素复合膜的柔韧性。当HPMC的添加量为乳清蛋白的20%时,复合膜的抗拉强度较好,表观光滑平整。制备WPC-HPMC复合膜进行奶茶粉、方便面调料包、油包,苏打饼干的初步包装实验,研究了包装产品在储藏12 d期间质量变化情况。结论:乳清蛋白-羟丙基甲基纤维素复合膜具有一定包装应用潜能。     

化学交联与酶法交联对鱼糜-明胶复合膜性质的影响

研究比较了戊二醛和谷氨酰胺转氨酶(TGase)对鱼糜-明胶复合膜的性质改良效果。当戊二醛的含量为蛋白质量的0.025%～0.1%时,膜的抗拉伸强度(TS)没有显著差异,但断裂延伸率(EAB)却随着戊二醛含量的增加而上升,当戊二醛含量增加到0.2%时,TS和EAB都出现了下降。然而,膜的TS和EAB都随着TGase的添加逐渐增加。虽然戊二醛和TGase都可以使蛋白发生交联,导致膜的固形物溶解率(FS)和蛋白溶解率(PS)下降,但是戊二醛的添加效果明显优于TGase。此外,戊二醛的添加会使膜的颜色变黄,而TGase不仅不会影响膜的色泽,还可以提高膜的透明性能。根据SDS-PAGE的结果,发现戊二醛和TGase都会使膜中蛋白分子发生交联形成高分子聚合物。FT-IR的分析结果表明,蛋白分子间的氢键作用随着TGase的添加逐渐减弱,随着戊二醛的添加出现先减弱后增强的趋势。     

酶法糖基化修饰对酪蛋白体外消化能力的影响

利用转谷氨酰胺酶（transglutaminase,TGase）催化制备壳寡糖（1 kDa）糖基化酪蛋白;十二烷基硫酸钠-聚丙烯酰氨凝胶电泳和反相-高效液相色谱证实糖基化修饰反应的发生;体外消化实验（胃蛋白酶＋胰蛋白酶）分析糖基化修饰反应对酪蛋白消化性的影响。结果表明：TGase成功催化壳寡糖连接到酪蛋白分子上,所制备的糖基化酪蛋白中氨基葡萄糖的导入量为6.86 g/kg;糖基化酪蛋白经体外模拟消化后,其水解度和三氯乙酸可溶性氮均低于酪蛋白对照物,糖基化酪蛋白消化物中出现了更多大分子质量的肽段,研究表明TGase途径糖基化修饰降低了酪蛋白的体外消化能力。     

超声和酶处理对乳化猪油体外消化特性的影响

本研究以猪油为原料,超声诱导脂肪晶体发生重排,采用谷氨酰胺转氨酶（transglutaminase,TG）交联 浓缩乳清蛋白作为乳化剂,制备改性乳化猪油,进而探讨乳化猪油未吸附蛋白含量的变化,并在体外消化模型中以 平均粒径、Zeta电位、游离脂肪酸释放量以及脂肪颗粒微观结构作为评价指标,对改性乳化猪油体外消化特性进行 研究。结果表明,超声和TG处理分别对乳化猪油产生不同的作用,超声处理后乳化猪油未吸附蛋白含量低于未处 理样品,乳化稳定性降低,而TG处理则提高了乳化猪油的乳化稳定性。超声处理后的乳化猪油在体外消化过程中 的游离脂肪酸的释放量、平均粒径显著高于未处理样品（P＜0.05）,Zeta电位明显低于未处理样品。而TG交联浓 缩乳清蛋白促使乳化猪油颗粒更加细小,在体外消化过程中游离脂肪酸的释放量显著降低（P＜0.05）。超声处理 的乳化猪油更易于消化,TG处理则减缓了乳化猪油的消化速率。     

Rheological and equilibrium properties of milk proteins and tara gum mixtures

The stability of aqueous purified tara gum (TG) mixtures with sodium caseinate (NaCas) and whey protein concentrate (WPC) was investigated. Phase diagram of TG–milk proteins mixtures was obtained by measuring the sedimented fraction or the rheological parameters. The rheological behaviour was also evaluated as function of NaCas and WPC concentration, considering the zero-shear rate viscosity and the relaxation time as response variables. The rheological parameters were determined by rotational rheometry. The studied solutions presented a meta-stable condition provided by the increase in viscosity, while mixtures with NaCas at low TG concentrations sedimentation by volume exclusion occurred. The rheological behaviour of NaCas and WPC aqueous solutions approached the Newtonian and shear-thickening model, respectively. The mixtures with TG showed a pseudoplastic behaviour, approaching the Cross model. The results indicated interaction between TG and the studied proteins, expressed by an increase of zero-shear viscosity and the relaxation time at higher gum concentration.     

The water vapour permeability,mechanical properties and solubility of fish gelatin–chitosan films modified with transglutaminase or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and plasticized with glycerol

The effect of glycerol on the mechanical and water barrier properties, as well as on the water solubility, of fish gelatin–chitosan films (4:1, w/w) cross-linked with TGase or EDC was determined. The addition of glycerol in concentrations up to 30% (of the substrate mass) to the fish gelatin–chitosan films modified with TGase or EDC did not change their solubility in buffers of pH 3 and 6 at 25 °C or during heating at 100 °C for 60 min. The chemical and enzymatic cross-linking of the components did not increase the water barrier properties of the films. WVP of the films modified with EDC and TGase was not affected by glycerol at concentrations up to 25% of the substrate mass. Tensile strength of the films decreased after modification of the components with TGase or EDC, respectively, by about 25% and 40%. The elongations of the enzymatically modified films containing 20% of glycerol and of chemically modified films containing 15% of glycerol were, respectively, about 8 and 13 times higher than those of unplasticized films; however, the tensile strengths of plasticized films were, respectively, 2.5 and 5 times lower.