转谷氨酰胺酶对大豆分离蛋白凝胶性的影响

以微生物来源的转谷氨酰胺酶(MTGase)对大豆分离蛋白(SPI)进行改性,主要考察了凝胶性的变化.结果显示,MTGase对SPI的凝胶性有明显的改善作用,且加酶量、pH、反应温度、底物蛋白浓度及反应时间均对凝胶性影响显著.改性SPI在加酶量为5 U/g、pH 8.0、反应温度为37℃、蛋白浓度为12%时凝胶性改善明显,随着MTGase作用时间的延长,SPI凝胶性也呈增加趋势.MTGase的作用使SPI凝胶的蛋白质分子间形成了空间的网络交错结构.     

氧化条件下没食子酸对猪肉肌原纤维蛋白结构及凝胶特性的影响

构建肌原纤维蛋白Fenton氧化体系（10μmol/L Fe Cl₃,100μmol/L V_C和1 mmol/L H₂O₂）,以没食子酸（10、50、100、150μmol/g蛋白）作为抗氧化剂添加到氧化体系中,通过测定蛋白质表面疏水性、色氨酸荧光强度、凝胶强度、保水性、白度、流变特性及微观结构,研究在氧化条件下,没食子酸的抗氧化效果及其对蛋白质结构和凝胶特性的影响。结果表明,随着没食子酸浓度的增加,蛋白质的表面疏水性逐渐增加,凝胶强度和保水性呈下降趋势,凝胶白度略有上升,其微观结构受到破坏;色氨酸荧光强度随没食子酸浓度的增加而增加,但在150μmol/g时略有降低;且较高浓度下（50、100、150μmol/g）,蛋白失去典型的流变特征。总的来说,低浓度没食子酸在起到抗氧化作用的同时,对肌原纤维蛋白结构及凝胶特性的影响较小,而较高浓度的没食子酸破坏了蛋白的凝胶结构。      

微生物谷氨酰胺转移酶对大豆分离蛋白凝胶性能的影响

研究了底物浓度、pH、酶浓度、温度、时间、离子浓度和二巯基苏糖醇(DTT)的添加对微生物谷氨酰胺转移酶(MTGase)诱导的大豆分离蛋白(SPI)凝胶强度的影响。结果表明,在SPI溶液中加入MTGase,可以使体系在低温下形成凝胶;SPI低于8%不能形成凝胶;pH7.0,酶量为30U/g蛋白,50℃水浴加热1h,NaCl为0.6N时,均可获得最高的凝胶强度;添加DTT,对体系无影响。     

谷氨酰胺转氨酶对山杏仁蛋白凝胶特性的影响

为提高山杏仁蛋白的凝胶特性,采用谷氨酰胺转氨酶(TG酶)作为交联剂,通过单因素实验研究了TG酶添加量、pH、交联温度、交联时间对蛋白凝胶硬度、弹性、内聚力的影响,并以凝胶强度为指标,利用响应面法对山杏蛋白形成条件进行优化。优化的TG酶交联山杏仁蛋白形成凝胶的条件如下:TG酶添加量17 U/g,交联温度43℃,pH为7.2,交联时间2.5 h时,此时凝胶硬度达到(135±7.14) g。结果表明利用TG酶交联山杏仁蛋白形成凝胶具有可行性,为提高山杏仁蛋白的功能性质和应用价值提供参考。     

Effect of microbial transglutaminase on spaghetti quality

ABSTRACT:  To examine the potential application of microbial transglutaminase (MTG) on semolina dough properties and quality of raw and cooked spaghetti, the effects of various MTG addition levels on the solubility of proteins, SDS-PAGE pattern of semolina dough proteins, and textural and structural properties of raw and cooked spaghetti were investigated using semolina from a high-protein good variety (MACS 1967) and a low-protein poor variety (PDW 274) durum wheat. To increase the concentration of lysyl residues and possibly enhance the extent of cross-linking of protein matrix by MTG, a commercial soy protein isolate (SPI) was added at a level of 3% (w/w) in combination with MTG, and its effect on semolina dough properties and spaghetti quality was investigated. The addition of MTG significantly decreased the solubility of semolina dough proteins. SDS-PAGE results showed that with increasing levels of MTG, a progressive decrease in the intensity of the bands corresponding to molecular weight of around 66 kDa was observed. Protein cross-linking reaction catalyzed by MTG resulted in changes in dough properties, dry spaghetti quality, cooking quality characteristics, and microstructure of cooked spaghetti. However, the quality improvements were more evident in spaghetti from the poor variety PDW 274 than from the good variety MACS 1967. The results also showed the ability of MTG in the formation of heterologous polymers between SPI and durum wheat proteins to improve the quality of spaghetti samples.     

Gelation properties of myofibrillar/pea protein mixtures induced by transglutaminase crosslinking

Gelation properties of mixtures of myofibrillar protein isolate (MPI)/pea protein isolate (PPI) were studied using a dynamic oscillatory rheometer and a texture analyzer to evaluate PPI as a possible meat product additive. The inclusion of microbial transglutaminase (MTG) increased the gel strength of MPI/PPI mixture (3% + 1%) more than it did for MPI (3%), but less than a 3% MPI, 1% soy protein isolate combination. The direct evidence of interaction between muscle and pea proteins in the form of new sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) bands was not found; however, the improvement in gel strength or gel peak force for the MPI/PPI mixture (3% + 1%) with inclusion of MTG suggested that some ? (γ-glutamyl) lysine (G-L) crosslinking occurred between muscle and pea proteins. It likely that pea protein acted as a non-gelling component and interspersed throughout the primary MPI gel network and the addition of MTG promoted partial crosslinking of MPI. Consequently, MTG is useful in improving gelation properties of heat-induced MPI/PPI gel.     

Emulsion properties of pork myofibrillar protein in combination with microbial transglutaminase and calcium alginate under various pH conditions

In this study, the effects of microbial transglutaminase (MTG) and calcium alginate (CA) systems in combination with soybean oil on the emulsion properties of porcine myofibrillar protein (MP) were evaluated under various pH conditions. MTG was shown to improve emulsifying capacity and creaming stability, which increased with increasing pH values up to 6.5. The CA did not influence emulsifying capacity, but it improved the creaming stability of the MP-stabilized emulsions. Both MTG and CA enhanced the rheological properties, but their effects on the physical characteristics of the protein evidenced an opposite trend in relation to pH, i.e., the MTG system improved both the emulsion and gelling properties with increasing pH, whereas the CA system was effective when the pH was lowered. By combining the two MP gelling systems, a stable and pH-insensible emulsion could be produced.     

谷氨酰胺转胺酶对谷朊质构和流变性质的影响

谷朊是淀粉加工的重要副产品。为了提高谷朊产量和改善谷朊性质,在制备谷朊的过程中,向面浆中加入微生物转谷氨酰胺酶(MTG)。结果表明,随着酶量的增加,谷朊的蛋白含量提高了3.98%。湿面筋的延伸性和回复性随酶量的增加逐渐减小。通过谷朊蛋白质分子羧基含量的测定和蛋白质分子间相互作用力的分析,在MTG作用100min后蛋白分子的羧基含量上升,蛋白质之间疏水相互作用明显减弱。研究表明,在微生物转谷氨酰胺酶(MTG)作用下谷朊的性质产生了明显的变化。     

Comparative study on protein cross-linking and gel enhancing effect of microbial transglutaminase on surimi from different fish

BACKGROUND: Microbial transglutaminase (MTGase) has been used to increase the gel strength of surimi. Nevertheless, its effectiveness varies with fish species. The aim of this study was to elucidate the effect of MTGase at different levels on protein cross‐linking and gel property of surimi from threadfin bream, Indian mackerel and sardine in the presence and absence of endogenous transglutaminase. RESULT: Breaking force of all surimi gels increased as MTGase levels (0–0.6 U g^?1) increased except for threadfin bream surimi gel, where the breaking force decreased at 0.6 U g^?1 (P < 0.05). In the presence of EDTA, the gel strengthening effect was lower, suggesting the combined effect of endogenous transglutaminase with MTGase. With the addition of MTGase, the gel with the highest increase in breaking force showed highest decrease in myosin heavy chain. When cross‐linking activity of MTGase on natural actomyosin (NAM) was determined, the highest decreasing rate in ε‐amino group content with the concomitant increased formation of cross‐linked proteins was found in NAM from threadfin bream. The reactivity of muscle proteins toward MTGase‐induced cross‐linking was in agreement with surimi gel strengthening. CONCLUSION: The composition and properties of muscle proteins of varying fish species more likely determined protein cross‐linking induced by MTGase, thereby affecting their gel properties. Copyright © 2011 Society of Chemical Industry     

Evaluation of red bean protein [Vigna angularis] isolate on rheological properties of pork myofibrillar protein gels induced by microbial transglutaminase

The effects of 1% red bean protein isolate (RBPI) on the gel properties of myofibrillar protein (MP) in various levels of microbial transglutaminase (MTG: 0%, 0.1%, 0.5%, & 1%) were evaluated. The cooking yield (CY) of the MP gels decreased with increasing MTG level, while the addition of RBPI improved the CY of the MP gels. Gel strength (GS) was also improved when RBPI was incorporated into the MP gels containing higher than 0.5% of MTG. The addition of MTG and RBPI was slightly changed the endothermic peak temperatures. Scanning electron microscopy (SEM) showed that the three‐dimensional structure of MP with RBPI alone or in combined with MTG was compacted as compared to the control. Based on the results, RBPI could be functioned as a substrate for MTG (0.5–1.0%) and a water binder of meat protein gel mediated by MTG.     

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.     

Evaluation of mungbean protein isolates at various levels as a substrate for microbial transglutaminase and water binding agent in pork myofibrillar protein gels

The objective of this study was to investigate the effect of mungbean protein isolate (MPI) on the potential possibility of water binding agent and as a substrate for the microbial transglutaminase (MTGase) in myofibrillar protein. Cooking loss (CL,%), gel strength (GS, gf), sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were measured. The addition of MPI reduced CL, indicating that it has a water binding capacity during cooking. The major protein band (53 kDa) of MPI appeared when MPI was mixed with MP, but it disappeared when MTGase was incorporated. MPI treatment changed the endothermic peaks as compared with those of CTL. MTGase (1%) mediated pork MP increased CL and GS (P < 0.05), and reduced peak temperatures with vanishing of endothermic intensity at 1st and 3rd peaks, suggesting the structural changes of protein gelation. In microstructures, MTGase treatment showed a finely stranded structure in MP gels, while MPI showed a conglomerated surface in MTGase‐mediated MP gels. These results indicated that MPI appears to be a water binding agent during cooking and function as a substrate for MTGase in MP gelation.     

P NMR spectroscopic investigations of caseins treated with microbial transglutaminase

Caseins - the main constituents of bovine milk proteins - self-assemble into large supramolecular aggregates, so-called casein micelles. The enhancement of the stability of casein micelles is advantageous with respect to technological milk processing. A promising approach to accomplish this goal is the cross-linking of caseins using microbial transglutaminase (mTG). The present paper describes the combined use of liquid- and solid-state ³¹P NMR spectroscopy as well as dynamic light scattering in order to characterize the influence of an mTG treatment upon the structure of micelles in ultrahigh temperature (UHT)-treated skim milk at a molecular level. Liquid-state ³¹P NMR spectroscopy was applied to characterize milk, milk serum and casein dispersions. A narrow SerP signal in the liquid-state ³¹P NMR spectra of UHT-treated milk is shown to be due to casein molecules in the milk serum whereas the casein molecules bound in the micelles give rise to broad signals. Most of the caseins contribute to a 3 kHz broad background signal which can be visualized in the spectrum of suspensions of re-dispersed micellar material derived from UHT-treated milk. Treatment with mTG results in a cross-linking of caseins, which could be followed by liquid-state ³¹P NMR spectroscopy. Especially, the cross-linking of β-casein was demonstrated by quantitative liquid-state ³¹P NMR experiments. Furthermore, the stability of cross-linked micellar aggregates against EDTA could be investigated by liquid-state ³¹P HR NMR in combination with dynamic light scattering (DLS). Solid-state ³¹P NMR was used to show that the motional state of the κ-caseins located at the outer surface of the micelles derived from UHT-treated milk is not significantly changed by the applied mTG treatment.     

Evaluation of pH‐treated fish sarcoplasmic proteins on rheological properties of fish myofibrillar protein mediated by microbial transglutaminase

Fish sarcoplasmic protein (SP) could be exploited in the water‐holding agent for fish protein gels, except that the gel strength is reduced. The adjustment of pH could modify protein interactions to overcome the inferior effect. Fish SP solutions were adjusted to pH 3 or 12, neutralised to pH 7 and lyophilised to be pH‐treated SPs. These SPs along with lyophilised untreated SP (Normal SP) were incorporated into fish myofibrillar protein (MP) with microbial transglutaminase (MTG). The denaturation temperature (T_d) of MP mixed with normal SP was 66 °C with the lowest shear stress value. The denaturation of MP mixed with pH‐treated SP reduced to be 57 °C, resulting in increased shear stress. The cooking loss of MP gel was reduced by adding pH‐treated SPs, while the breaking forces were similar to control. The result indicated that pH‐treated SPs could be used to reduce cooking loss of MTG‐mediated MP gels without affecting the gelling properties.