性早熟蟹肉和白鲢鱼糜混合凝胶工艺优化及其凝胶特性

通过向白鲢鱼糜中添加蟹肉和0.3%谷氨酰胺转氨酶（transglutaminase,TG）,以凝胶强度和持水性为指标,研究蟹肉比例、凝胶化时间以及凝胶化温度3 个因素对混合凝胶特性的影响。在单因素试验基础上,采取3因素3水平的Box-Behnken设计进行响应面分析,得到最佳工艺条件为：蟹肉比例10%,凝胶化时间3.0 h,凝胶化温度35 ℃。验证实验结果显示,与传统鱼肠相比,优化后的鱼糜与蟹肉混合肠,其凝胶强度有显著的提升（P＜0.05）,持水性略有降低,但并不显著（P＞0.05）;聚丙烯酰胺凝胶电泳和扫描电镜结果表明,TG的添加可使混合凝胶中肌球蛋白重链明显减少,且凝胶表面更均匀、致密。     

超声-转谷氨酰胺酶改善红豆蛋白功能性质及结构

采用超声联合转谷氨酰胺酶（transglutaminase,TG）处理红豆分离蛋白（red bean protein isolate,RBPI）,对其功能性质和结构特征进行分析,以探究其结构修饰与功能性质的构效关系。结果表明：超声处理5 min能够使RBPI的乳化活性和发泡能力提高,但会降低泡沫稳定性,对乳液稳定性没有显著影响,同时增加表面疏水性和游离巯基含量;TG能够提高RBPI的乳化活性、乳化稳定性及泡沫稳定性,但会降低发泡能力、表面疏水性和游离巯基含量;超声-TG联合处理的RBPI具有更高的乳化活性和泡沫稳定性,更低的表面疏水性和游离巯基含量,且酰胺Ⅰ带处吸收峰强度增加,更多的无规卷曲结构转变为有序的β-折叠结构,这可能是导致RBPI功能性质改善的原因。超声处理5 min联合TG诱导的蛋白凝胶具有更加均匀、致密的微观结构,且凝胶硬度和黏附力增加,脱水收缩作用降低;峰值温度（Tp）和热焓变（ΔH）显著增加（P＜0.05）,改善了RBPI的热稳定性或三级结构稳定性。以上结果表明RBPI经过超声处理后更利于TG对蛋白质的交联作用,超声-TG联合处理促进了蛋白质功能性质的发挥。     

大豆分离蛋白、木薯淀粉与转谷氨酰胺酶组合对鲢鱼鱼糜凝胶品质的影响

探究了大豆分离蛋白、木薯淀粉及转谷氨酰胺酶对鲢鱼鱼糜制品的影响并确定最适添加量。结果表明,当大豆分离蛋白添加量6%,木薯淀粉添加量9%以及转谷氨酰胺酶添加量4U/g·蛋白时,能有效增加鱼糜的持水性,降低其蒸煮损失,且不会使鱼糜带有大豆分离蛋白的淡黄色,同时提高了鱼糜的凝胶强度,鲢鱼鱼糜制品各项指标较好。通过低场核磁共振和扫描电镜检测发现,未添加的对照组在6次冻融后凝胶结构完全被破坏,不易移动水峰面积(A_(23))下降了25%,试验组凝胶结构比较致密,A_(23)下降了11%,进一步验证了此配方组合对鱼糜在冻融循环过程中凝胶结构的稳定性具有保护作用。     

Gelation properties of chicken myofibrillar protein induced by transglutaminase crosslinking

Gelation properties of chicken myofibrillar protein isolate (MPI) and the effect of microbial transglutaminase (MTG) were studied using a dynamic oscillatory rheometer and a texture analyzer. Final heating temperature had a great impact on gel stiffness and the maximum gel stiffness was obtained at 95 °C. pH and ionic strength also influenced gel stiffness and the maximum gel stiffness was achieved at pH 6, 0.9 M NaCl; however, less stiff gels were formed in 0.6 and 1.2 M NaCl. In the MPI concentration range of ∼0.5-5%, a positive correlation was observed between gel stiffness or gel peak force and MPI concentration. When MTG was included at levels of ∼0 to 12-15 U, positive linear relations were found between gel stiffness or peak force and MTG levels. However, negative correlations for these parameters were observed at higher MTG concentrations. When MTG level was greater than 15 U, gel stiffness or peak force tended to decrease. The improvement in gel strength or gel peak force for the MPI with inclusion of MTG suggested that some ε (γ-glutamyl) lysine (G-L) crosslinking occurred among myofibrillar molecules. Thus, MTG is useful in improving gelation properties of heat-induced MPI gel and provides new opportunities to expand the utilization of low value meat in muscle foods.     

酪蛋白的转谷氨酰胺酶酶促糖基化交联条件及产物性质

在氨基葡萄糖存在的条件下,利用转谷氨酰胺酶(EC2.3.2.13)对酪蛋白进行糖基化交联修饰。以修饰酪蛋白产物中氨基葡萄糖的导入量为指标,采用单因素试验分别考察反应体系pH值、酶添加量、反应温度和时间对修饰反应的影响。优化后的适宜修饰条件为:酪蛋白底物质量浓度为30g/L,氨基葡萄糖添加量为3mol(每kg酪蛋白中)、pH值为7.5、酶添加量为10kU(每kg酪蛋白中)、反应温度为37℃、时间4h。与酪蛋白和转谷氨酰胺酶促交联的酪蛋白相比,修饰酪蛋白产物的乳化性质和胶凝性质得到显著改善,并且体外消化性能未受到影响,表明转谷氨酰胺酶催化的糖基化交联修饰可以用于改善酪蛋白的这些功能性质。     

转谷氨酰胺酶交联酶晶体的制备及其结构表征

采用双功能试剂戊二醛对转谷氨酰胺酶晶体进行化学变联,得到交联条件.对交联酶晶体用电镜扫描以及红外光谱和XPS进行结构表征.交联条件:戊二醛质量分数1％,交联pH 6,交联温度4℃,交联时间40min.红外光谱显示,游离酶在1 651 cm-1出现强峰,而交联酶晶体在1 634、1 281和1 241 cm-1出现峰值,在α-螺旋区域没有检测到峰值.通过X-射线光电子能谱分析证实,交联酶晶体与游离酶相比,在285.1 eV处的C1S的信号峰增强,在400.375 eV处的NlS峰几乎消失,说明酶蛋白表面的游离氨基已经与戊二醛结合,表面蛋白结构发生了变化.     

转谷氨酰胺酶对大豆蛋白粘度的影响

利用转谷氨酰胺酶(TGase)对大豆蛋白进行改性,并对其粘度进行研究。随着TGase加量的增加,蛋白溶液的粘度不断增加。脱脂豆粉(LTSP)、大豆分离蛋白(SPI)和11S蛋白的粘度均在45℃时最大,而大豆7S蛋白在温度为50℃时粘度最大。随反应时间的延长,体系粘度呈先增加后减少的趋势,大豆11S蛋白的粘度在反应时间为90min时达到最大,其他三种蛋白在120min时粘度最大。     

三种添加剂在鱼肉猪肉复合凝胶中的作用

为了改善鱼肉/猪肉复合肉糜（配比分别为3：7和7：3）的凝胶性能,研究了添加剂（TGase、CaCl2和焦磷酸钠）对鱼肉/猪肉复合凝胶的作用效果。结果表明,两种复合肉糜凝胶的破断强度、凝胶强度和保水性均随着TGase添加量的增加而增大,对鱼肉/猪肉（7：3）复合凝胶的增强作用更显著,而且降低了鱼肉/猪肉（7：3）复合凝胶的白度。CaCl2的添加也可增大复合肉糜的凝胶强度和白度,但高剂量的CaCl2（〉10mmol/kg）会降低其保水性。鱼肉/猪肉为7：3和3：7复合凝胶的凝胶强度分别于焦磷酸钠为0.05%和0.3%时达到最大值,高剂量的焦磷酸钠（〉0.3%）会提高复合凝胶的持水性,而对白度的影响较小。     

TGFβ-1 Induced Cross-Linking of the Extracellular Matrix of Primary Human Dermal Fibroblasts

Excessive cross-linking is a major factor in the resistance to the remodelling of the extracellular matrix (ECM) during fibrotic progression. The role of TGFβ signalling in impairing ECM remodelling has been demonstrated in various fibrotic models. We hypothesised that increased ECM cross-linking by TGFβ contributes to skin fibrosis in Systemic Sclerosis (SSc). Proteomics was used to identify cross-linking enzymes in the ECM of primary human dermal fibroblasts, and to compare their levels following treatment with TGFβ-1. A significant upregulation and enrichment of lysyl-oxidase-like 1, 2 and 4 and transglutaminase 2 were found. Western blotting confirmed the upregulation of lysyl hydroxylase 2 in the ECM. Increased transglutaminase activity in TGFβ-1 treated ECM was revealed from a cell-based assay. We employed a mass spectrometry-based method to identify alterations in the ECM cross-linking pattern caused by TGFβ-1. Cross-linking sites were identified in collagens I and V, fibrinogen and fibronectin. One cross-linking site in fibrinogen alpha was found only in TGFβ-treated samples. In conclusion, we have mapped novel cross-links between ECM proteins and demonstrated that activation of TGFβ signalling in cultured dermal fibroblasts upregulates multiple cross-linking enzymes in the ECM.