Sodium Caseinate and Skim Milk Gels Formed by Incubation with Microbial Transglutaminase

Several suspensions and emulsions containing commercial sodium caseinate or skim milk were gelatinized by Ca²⁺-independent microbial transglutaminase treatment. The characteristics of the gels were largely affected by the enzyme concentrations employed. For caseinate gels generally the higher enzyme concentration gave steep decreases in breaking strength, strain and cohesiveness of the gels. The creep tests on emulsified gels prepared to two different enzyme concentrations showed that the gel made with a higher enzyme concentration was the more viscoelastic. For skim milk gels, the enzyme treatment in higher concentration caused substantial increase of the breaking and hardness while the strain and cohesiveness had little or no changes.     

Physical Properties of Soy Bean and Broad Bean 11S Globulin Gels Formed by Transglutaminase Reaction

Physical properties of transglutaminase-induced glycinin and legumin gels were compared with thermally induced gels. Results of deformation tests showed that transglutaminase-induced gels were more rigid and elastic than thermally induced gels. From creep compliance tests, all elastic moduli and viscosities except Newtonian viscosity were higher for transglutaminase-induced gels. Electron micrographs revealed that network structures of transglutaminase-induced gels were composed of larger unit particles forming more developed strands and clusters. More rigid and elastic gels were formed from glycinin as compared to legumin by both gelling methods.     

Dough Properties and Crumb Strength of White Pan Bread as Affected by Microbial Transglutaminase

Microbial transglutaminase forms nondisulfide covalent crosslinks in proteins and is being used in foods. This enzyme may produce beneficial effects during breadmaking that are comparable to traditional oxidizing improvers, hypothesized to act via formation of disulfide crosslinks. Transglutaminase greatly improved the crumb strength of baked loaves and provides a potential solution to a common consumer complaint. Transglutaminase also reduced the required work input and substantially improved the water absorption of the dough. Each of these effects would lower processing costs for commercial baking     

Gel Strength Enhancement by Addition of Microbial Transglutaminase during Onshore Surimi Manufacture

Surimi from Alaska pollock flesh was manufactured onshore with Microbial transglutaminase (MTGase). Effect of MTGase was investigated by evaluating breaking strength and deformation of gels from MTGase-treated surimi with and without setting at 30°C. Quantitative analysis of ε-(γ-glutamyl)lysine (GL) crosslink was also carried out to monitor the MTGase reaction. In set gels, breaking strength and GL crosslink increased, and myosin heavy chain decreased correspondingly with MTGase concentration. These changes were smaller in gels prepared without setting. Results suggest that surimi gel could be improved through the formation of GL crosslinks by added MTGase in surimi.     

大豆蛋白凝胶显微结构研究

使用盐卤、葡萄糖酸内酯和转谷氨酰胺酶制备大豆蛋白凝胶,为了真实反映大豆蛋白凝胶的结构,分别采用戊二醛和乙醇2种固定剂固定形成的凝胶结构.通过扫描电子显微镜(SEM)观察不同的凝固剂和固定剂处理的大豆蛋白凝胶的显微结构,结果表明戊二醛和乙醇都能起到固定凝胶网络结构的效果,由0.7％(质量体积比)盐卤、0.06 mol/L葡萄糖酸内酯、40 kat/g转谷氨酰胺酶制备的凝胶的网孔较多.此外通过物性分析仪分析凝胶硬度,结果表明100％乙醇固定的凝胶硬度比戊二醛固定凝胶的硬度大.     

微生物转谷氨酰胺酶对大豆分离蛋白乳液凝胶性能的影响

研究了不同油相比例（φ=0.2~0.6）的微生物φ转谷氨酰胺酶（MTGase）诱导的大豆分离蛋白（SPI）乳液凝胶性能及微观结构,发现提高乳液中的油相比例,凝胶的弹性模量G’及凝胶持水性均有显著提高并存在一定相关性,乳液凝胶形成的凝胶网络机械强度更大,油滴在酶促乳液凝胶中充当了良好的＂活性填充剂＂。     

转谷氨酰胺酶催化大豆蛋白和乳清蛋白合成耐热性聚合蛋白

用商品级转谷氨酰胺酶(TG-B)聚合大豆蛋白和乳清蛋白形成高耐热、耐酸的蛋白聚合物。蛋白聚合物的合成量由SDS-PAGE电泳结合凝胶成像分析测定;蛋白聚合物的耐热性用差示扫描量热法(DSC)测定;蛋白聚合物的酸溶解性用双缩脲法测定。结果表明TG-B聚合大豆蛋白和乳清蛋白形成的蛋白聚合物的最适条件为pH为6～7;反应温度30℃～45℃,反应时间4h,加酶量为6当量单位/g蛋白,在此条件下蛋白聚合物的转化量可达30%,所合成蛋白聚合物可耐130℃的热处理而不发生变性;并在pH3.2～4.3范围不发生沉淀。     

转谷氨酰胺酶对大豆分离蛋白交联聚合作用研究

该文研究利用微生物来源的转谷氨酰胺酶(MTGase)对大豆分离蛋白进行交联聚合,研究不同反应条件对聚合反应影响,并对聚合后蛋白凝胶性进行研究。结果显示,大豆分离蛋白是MTGase良好底物;得到较好聚合反应条件为:温度45℃或50℃;pH7.0;反应时间2 h时最适加酶量为5U/g。聚合后蛋白凝胶特性,尤其是凝胶硬度和粘性有较显著提高。     

谷氨酰胺转氨酶菌株的筛选及其产酶条件研究

利用蛋白质交联-絮凝沉淀性能测定方法,从土壤中分离得到1株高产谷氨酰胺转氨酶(microbial transglutaminase,MTG)的菌株,命名为HF-82,初步确定为链霉菌属。单因素试验确定最适产酶氮源和碳源分别是蛋白胨和葡萄糖,正交试验确定最适发酵培养基为(g/L):葡萄糖25.0,蛋白胨20.0,酵母提取物5.0,Mg SO4·7 H2O 2.0,K2HPO4·3 H2O 2.0,Na H2PO42.0,Ca CO33.0,p H7.0。此发酵工艺条件下,MTG的酶活可达到0.53 U/m L。     

利用微生物谷氨酰胺转胺酶提高香肠制品的物性

在香肠产品加工中根据原料中的粗蛋白含量添加一定量的微生物谷氨酰胺转胺酶处理后 ,采用质构分析仪测定香肠组织的凝胶破坏力的变化 ,研究了酶催化加工工艺条件和酶对香肠物性的增强效果。实验结果表明 ,将该酶加入到香肠中 ,40℃下酶作用 45min ,再经过干燥、蒸煮等工艺处理成型后 ,凝胶强度比对照组提高了 60 %以上 ,产品的粘弹性得到显著提高。同时在加工工艺不变的条件下 ,增加香肠配方中淀粉和大豆蛋白粉的比例 ,加入量增加到 5 %时 ,与原配方比较 ,产品的质地和感官指标并无显著差别 ,可达到降低成本的目的     

Microcentrifuge-Based Method for Measuring Water-Holding of Protein Gels

A method developed to measure water-holding properties of protein gels provides high precision and expanded analysis. A cylindrical gel sample was placed in an inner cell (which at its base contained a filter membrane) of a commercial microfiltration unit. The unit was then spun in a horizontal rotor microcentrifuge. Rates of water loss and degree of compression were determined. The rate of water loss could be modeled as the summation of two exponential decay functions. Degree of compression correlated with held-water. Gel rehydration ability and microstructure were used to study effects of centrifugal compression on gel structure.     

Properties of Acidic Whey Protein Gels Containing Emulsified Butterfat

Changes in physical properties of whey protein gels following addition of emulsified fat were investigated. Gels were made by heating mixtures of dialyzed whey protein isolate at pH 4.60 with and without emulsified fat droplets. Addition of emulsified fat improved the gel-like qualities of these systems. Gel strength progressively increased upon addition of emulsified fat up to 30.00% by weight. Mean droplet size 1.85 km produced the greatest reinforcement of gel strength. Gels made with intermediate concentrations of protein were most sensitive to the effect. The elastic moduli and viscosities of whey protein gels at pH 4.60 increased with fat content, whereas syneresis decreased upon addition of fat.     

乳清蛋白冷凝胶对双歧杆菌的保护

以CaCl_2和葡萄糖酸-δ-内酯(glucono-δ-lactone,GDL)作为凝胶剂,采用酸耐受性实验为评价指标,确定乳清蛋白冷凝胶工艺参数,并借助扫描电子显微镜观察凝胶结构,探讨采用盐和酸诱导乳清分离蛋白(whey protein isolate,WPI)所形成的包含双歧杆菌冷凝胶对双歧杆菌的保护作用。结果显示,0.30%的GDL诱导5%WPI和6%WPI形成的颗粒状冷凝胶,在pH1.5的酸环境下对双歧杆菌的保护性最好,作用120 min后菌落数下降2个数量级,菌体存活率分别达到1.7%和2.1%。制各出的乳清蛋白冷凝胶对双歧杆菌有良好的保护性,为益生菌产品的开发和扩展应用提供了参考。     

谷氨酰胺转氨酶对大豆蛋白／PVA 复合薄膜性能的影响

以大豆蛋白和聚乙烯醇（ PVA）为主要原料,以抗张强度、断裂伸长率、透光率、吸水率为评价指标,通过单因素试验和正交试验,研究了谷氨酰胺转氨酶（简称TG）对大豆蛋白/PVA复合薄膜性能的影响。试验结果表明：当反应pH为5．0,反应温度为55℃,TG添加质量分数为0．20‰时得到性能最佳的复合薄膜;在最佳条件下,薄膜的抗张强度、断裂伸长率、透光率和吸水率分别为8．06 MPa,89．97％,30．8％和46．43％。     

Microbial Transglutaminase and ε-(γ-Glutamyl)lysine Crosslink Effects on Elastic Properties of Kamaboko Gels

Kamaboko gels from Alaska pollock surimi (SA? and 2nd? grades) were prepared by setting at 10 or 45°C with Microbial transglutaminase (MTGase) and its effect on gel properties was investigated. At 10 and 45°C, gels from 2nd? grade surimi paste showed increases in breaking strength, without decline in deformation. Gel from SA? graded surimi paste showed an increase in breaking strength with no changes in deformation in 45°C setting, up to 0.03% MTGase. Crosslinking of myosin heavy chains through ε-(γ-glutamyl)lysine bonds was observed and a possible correlation was shown between ε-(γ-glutamyl)lysine content and gel strength (breaking strength X strain). ε-(γ-Glutamyl)lysine content up to 3 μmol/100g or MTGase 0.03% or higher improved gel properties.     

Microstructure of Whey Protein Isolate Gels Containing Emulsified Butterfat Droplets

The effects of concentration and droplet size of anhydrous butterfat globules on the microstructure of heat-induced whey protein isolate gels (pH 4.60) were studied by scanning and transmission electron microscopy (TEM). All fat globules were emulsified with whey protein isolate and incorporated into the system prior to gelation. Protein aggregates became more closely packed as whey protein concentration was increased from 8 to 15% by weight in gels without added fat. There was no notable change in overall gel microstructure upon addition of fat globules, up to 25% by weight, when viewed by scanning electron microscopy. However, it appeared fat globules were intimately associated with the gel protein matrix. A twofold difference in fat globule size was obvious by TEM. Clusters of droplets became more predominant as butterfat content increased.     

Use of Soy Protein and Microbial Transglutaminase as a Binder in Low-sodium Restructured Meats

ABSTRACT: Pork sticks were prepared by mixing pork chucks with various amounts of bisulfite-treated soy protein and microbial transglutaminase (MTGase) to evaluate the potential of using soy protein as meat binders. According to tensile strength, the favorable conditions for binding the restructured pork chunks were 5% soy protein containing 0.2% NaHSO₃ and 20 unit MTGase/g, and the setting condition was 60 min at 40°C. The tensile strength and cooking yield of restructured pork sticks made with bisulfite-treated soy protein and MTGase were much higher than those of using salt, suggesting the high potential of using soy protein and MTGase as binders in products where NaCl reduction is desired.     

酶法改性对各种蛋白膜的溶解特性和体外消化率的影响

以大豆分离蛋白SPI-1、大豆分离蛋白SPI-2、酪蛋白酸钠NaCas-1、酪蛋白酸钠NaCas-2、明胶G-1、明胶G-2、乳清蛋白浓缩物WPC、小麦面筋蛋白WG、花生分离蛋白PPI这9种蛋白质为原料制备蛋白膜,主要研究了谷氨酰胺转移酶(TGase)改性对这9种蛋白膜的溶解特性和体外消化率这2种性能的影响。TGase的作用使SPI-1膜、NaCas膜和WPC膜的水分含量呈显著性降低(P≤0.05)。TGase的处理使各种蛋白质膜的总可溶性物质量均比对照膜明显降低,SDS-PAGE分析表明,TGase作用明显降低了这几种蛋白膜在水溶液中的溶解性。与对照膜相比,TGase改性显著降低了蛋白膜的消化率,其中NaCas、SPI和G蛋白膜的下降幅度较大。这可能是因为TGase催化改性的蛋白膜中产生了新的交联。     

影响鸭肉肌原纤维蛋白凝胶保水性的因素研究

以鸭胸肉为材料,提取鸭肉中的肌原纤维蛋白,研究溶液环境(蛋白浓度、NaCl浓度、pH)和加热方法(加热温度、加热时间、加热速率),对肌原纤维蛋白热诱导凝胶保水性的影响。研究结果表明:在一定范围内,鸭肉肌原纤维蛋白凝胶的保水性与蛋白溶解度呈正相关;随着蛋白浓度越大,NaCl浓度升高,凝胶保水性也相应提高;pH偏离蛋白的等电点越远,保水性越好;加热温度为70℃,加热时间为20 min,加热速率0.2℃/min～0.5℃/min,凝胶保水性最好。     

κ-卡拉胶对大豆分离蛋白乳浊凝胶特性的影响

研究了κ 卡拉胶在不同pH的条件下对大豆分离蛋白乳浊凝胶质构特性和流变特性的影响。研究结果表明 ,pH 7 3条件下的乳浊体系比 pH 6 8的体系更易形成凝胶。卡拉胶质量分数为 0 0 5 %时 ,因与大豆分离蛋白发生静电吸引相互作用形成连接型凝胶而显著提高了凝胶的质构特性和流变特性。 0 2 %时则形成相分离型凝胶 ,降低了凝胶的弹性和内聚性。