Effect of mungbean [Vigna radiata (L.) Wilczek] protein isolates on the microbial transglutaminase‐mediated porcine myofibrillar protein gels at various salt concentrations

This study was performed to investigate the effects of mungbean protein isolates (MPI) as a meat/water binder on the MTGase‐mediated porcine myofibrillar protein (MP) gels at 0.15, 0.3, and 0.45 m salt concentrations. The general property of MP gel was evaluated by pH, cooking loss (CL) (%) and gel strength (gf). Protein–protein interactions among MPI, MTGase, and MP during cooking were also assessed using gel electrophoresis, thermal analysis and microstructure. When salt content was reduced, gel CL (%; P < 0.05) was increased while pH and gel strength (gf) values were decreased (P < 0.05). Addition of MTGase to MP increased pH, CL (%), and gel strength (gf) values, while co‐addition of MTGase and MPI induced synergistic effects on the MP gel strength (gf; ≥0.3 m salt concentration; P < 0.05). In scanning electron micrograph images, increase of salt concentrations made MP gels more swollen and interwoven or conglomerated, regardless of treatment. In conclusion, addition of MPI and MTGase strengthened gel‐forming ability and improved cooking yield of MP gel at salt concentration (≥0.3 m ).     

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.     

羟自由基氧化对鲢鱼肌原纤维蛋白凝胶特性的影响

采用含不同浓度H₂O₂(0.0～10.0 mmol/L)的Fenton体系(H₂O₂-VC-FeCl₃)模拟氧化应激环境对鲢鱼肌原纤维蛋白进行氧化,测定蛋白的巯基含量,以及蛋白凝胶的凝胶强度、白度、持水性、水分分布状态及微观结构,探究氧化度对蛋白凝胶特性的影响。结果表明：随着H₂O₂浓度的增加,蛋白的总巯基含量和白度、持水性呈先升高后降低的趋势。当体系中H₂O₂浓度较低(0.1～0.5 mmol/L)时,蛋白凝胶强度增大,白度得到改善;凝胶的三维结构孔洞的面积较小,且分布较为均匀,凝胶的持水力有所增强。但是当体系中的H₂O₂浓度较高(5.0～10.0 mmol/L)时,蛋白凝胶的白度下降,凝胶结构的有序性降低,孔洞面积变大,分布变得不均匀,凝胶的持水力下降,凝胶品质发生劣变。因此,适度氧化(0.1～0.5 mmol/L H₂O...     

Effects of Agaricus bisporus on gel properties of chicken myofibrillar protein

The gel-forming ability of myofibrillar protein (MP) is highly correlated with the characteristics of emulsified meat products. Incorporation of Agaricus bisporus (Ab) powder into MP gels may enhance its gel properties to facilitate the development of a novel and safe meat product. Therefore, this study investigated the effects of Ab powder on gel strength, water holding capacity (WHC), texture, rheological behaviour, LF-NMR spin–spin relaxation (T₂), microstructure and protein secondary structure of the MP gel system. The results indicated that the gel strength, WHC, G' value and G" value were significantly improved when the addition of Ab powder increased from 0% to 6% (P < 0.05). Meanwhile, the T₂ relaxation time was shortened, and free water was transformed into immobilised water. The texture of the gel was improved when 1%–4% Ab powder was added compared to the control. Furthermore, Ab filled in the gel network and promoted the unfolding of MP α-helix and the formation of MP β-sheet during the thermal denaturation of MP, leading to a dense aggregated network structure. The study suggested that Ab could be a promising ingredient in improving chicken MP's gel properties and developing fat-reduced meat products.     

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 various salt contents on quality characteristics with or without curdlan of pork myofibrillar protein gels and the development of low-salt pork sausages

The objective of this study was to evaluate the gelling properties of pork myofibrillar protein (MP) gels at various salt concentrations with or without curdlan, and its application to model sausages with reduced salt levels. When curdlan was incorporated into MP mixtures, cooking yield (CY) at 0.15 m salt was similar to that of 0.45 m salt (P > 0.05). Gel strength of MPs at 0.45 m salt was highest among other salt concentrations. Increased salt concentration tended to be high shear stress values, regardless of the presence of curdlan (P < 0.05). MP gels with increasing salt concentration showed fewer pores and swollen structures. Addition of curdlan improved CY and expressible moisture of low-fat model sausage with increased salt levels. The addition of curdlan at 1.0% salt reduced the hardness and gumminess, and similar to those at 1.5% without curdlan. These results indicated that curdlan improved the water-holding capacity and textural properties of low-fat and low-salt sausage.     

脱乙酰魔芋葡甘聚糖对猪肉肌原纤维蛋白结构及凝胶特性的影响

研究添加不同质量分数（0%、0.125%、0.25%、0.5%和1%）的脱乙酰魔芋葡甘聚糖（deacetylated konjac glucomannan,DKGM）对猪肉肌原纤维蛋白（myofibrillar protein,MP）结构和凝胶性能的影响,通过分析其凝胶强度、保水性、水分分布、微观结构和凝胶分子力的变化,探究DKGM对MP凝胶特性的影响机制。结果表明,MP凝胶强度随着DKGM质量分数的增加而增大,添加量为0.25%时达到峰值,是对照组的1.55倍;DKGM的加入可以减缓水的流动性,从而提高凝胶持水力;冷场扫描电子显微镜观察发现添加DKGM可以促进凝胶形成更为均匀致密的网络结构;结构和作用力分析表明适量添加DKGM可以促进MP分子的展开和疏水基团的暴露,增加活性巯基的含量,诱导更多α-螺旋向β-折叠转变,增强MP凝胶的疏水相互作用和二硫键,从而改善MP凝胶强度和持水力。     

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.     

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.     

安石榴苷与焦磷酸钠对肌原纤维蛋白氧化稳定性及凝胶性能的影响

研究添加安石榴苷、焦磷酸钠（sodium pyrophosphate,SPP）及其组合（P＋SPP）对肌原纤维蛋白（myofibrillar protein,MP）氧化稳定性和凝胶性能的影响。结果表明,安石榴苷和SPP添加均能有效抑制氧化诱导的蛋白羰基含量上升及自由氨基含量下降,且P＋SPP组合添加效果最佳;但所有添加剂均无法有效抑制氧化诱导的巯基含量降低。添加安石榴苷促进了氧化诱导的蛋白结构展开、显著抑制了蛋白粒径增大（抑制率为10.50%）,对于蛋白溶解度和热诱导凝胶过程中的流变学特性无显著影响,但明显降低了氧化MP凝胶的蒸煮损失和质构劣变。SPP添加同样促进了蛋白结构展开、抑制了蛋白粒径增大（抑制率为17.65%）、提高了氧化MP的溶解度（提高了9.78%）,显著改变了热诱导凝胶过程中MP的流变学行为,致使热诱导凝胶的蒸煮损失降低了42.56%,但明显降低了凝胶强度等质构指标。P＋SPP对MP凝胶性能的影响整体与SPP单独添加类似。因此,本研究抗氧化剂使用显著提高了MP的氧化稳定性及凝胶持水性,但凝胶的质构特性与抗氧化剂的种类密切相关。     

Xanthan Enhances Water Binding and Gel Formation of Transglutaminase-Treated Porcine Myofibrillar Proteins

ABSTRACT: In this study, the effect of xanthan on dynamic rheological properties, textural profile, and water binding of transglutaminase (TG)-treated myofibrillar protein (MP) gels was investigated. In experiment 1, MP suspensions (40 mg/mL protein, 0.6 M NaCl) at pH 6.45 with or without 0.05% xanthan were treated with 0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% TG; in experiment 2, MP suspensions (40 mg/mL protein, 0.6 M NaCl) at pHs 6.13, 6.30, 6.45, 6.69 with or without 0.05% xanthan were treated with 0.3% TG. Treated samples were analyzed with differential scanning calorimetry for thermal stability and oscillatory rheometry and Instron penetration tests for gelation properties. The TG treatments lowered the transition temperature (T_m) of MP by as much as 6 °C (P < 0.05) but increased apparent enthalpy of denaturation. However, there was no detectable thermal stability difference between MP samples with or without xanthan. The shear storage modulus (G′) of MP gels increased markedly upon treatments with ≥0.3% TG, and the presence of xanthan further enhanced the gel strength (P < 0.05). The addition of 0.05% xanthan decreased cooking loss of TG-treated MP gels by 17% to 23% when compared with gels without xanthan at all pH levels evaluated (6.13 to 6.67). Thus, the combination of TG and xanthan offered a feasible means to promote cross-linking and gelation of MP while reducing cooking losses.     

Casein gelation under simultaneous action of transglutaminase and glucono-delta-lactone

Casein solutions (5% w/v) were treated with microbial transglutaminase (MTG) and glucono-delta-lactone (GDL) under varying conditions in order to obtain gels. Storage modulus (G') and gelation time of the gels were measured by oscillation rheometry, while protein cross-linking was determined by gel permeation chromatography. The addition of only GDL to milk resulted in very weak gels, while MTG on its own was not able to create gel networks. Simultaneous action of both ingredients led to gels, the firmness of which was linearly related to the added amount of MTG, but passed through a maximum with rising GDL concentrations. Using chromatographical analysis, increasing G' values were interrelated with the formation of MTG-induced oligomers. The gelation time was directly proportional to the GDL concentration but not influenced by the addition of MTG within the studied range of concentration.     

Gelation properties of salt-extracted pea protein isolate catalyzed by microbial transglutaminase cross-linking

Gelation is a fundamental functional characteristic of plant proteins. In this paper, a salt-extracted pea protein isolate (PPI) was mixed with microbial transglutaminase (MTG) to produce gels and the gelation properties were studied. When the MTG level increased, the magnitude of both the G′ and G″ moduli also increased, which means the gel strength increased. A second order polynomial equation was used to describe the relationships between the G′, G″ modulus and TG level. It was found that with increased heating and cooling rate at the same MTG level, G′ and G″ tended to decrease, resulting in a weaker gel. This was attributed to the rearrangement time of pea protein molecules; slower heating and cooling rates enabled protein molecules to have more time to rearrange and therefore form a stronger gel. At the same MTG level, higher pea protein concentration resulted in higher G′ and G″ values and a power law relationship was found between G′ and pea protein concentration or G″ and pea protein concentration. Frequency sweep data of PPI show that the MTG treatment resulted in higher G′ values and lower tan delta values, indicative of a stronger more elastic gel. The minimum gelation concentration was found to be 3% (w/v) with 10 U MTG treatment, lower than 5.5% required when no MTG was present. When compared to PPI and soy protein isolate (SPI) with and without 10 U MTG treatment, the gel strength of PPI with MTG was stronger than that of SPI with MTG treatment, whereas the opposite was true without the MTG treatment. SDS-PAGE showed that at the same pea protein concentration, higher MTG level induced more cross-linking as fainter bands were seen on the gel and there was a shift in the relative intensities of the bands in the molecular weight range of 35–100 kDa.     

肌原纤维蛋白氧化对谷氨酰胺转移酶介导的交联反应及凝胶性的影响

研究不同盐浓度下肌原纤维蛋白的氧化对后继的微生物谷氨酰胺转移酶(MTG)交联反应及凝胶能力的影响。分散在三种盐浓度(0.15、0.45和0.6mol/L NaCl)下的肌原纤维蛋白在4℃分别氧化2h和24h,然后在0.6mol/L NaCl条件下加入MTG于30℃交联2h。通过电泳和溶解度研究蛋白的氧化对MTG交联反应的影响,通过凝胶强度研究蛋白的氧化对MTG交联反应后凝胶性的影响。研究表明,三种盐浓度下的氧化都会促进MTG交联反应,特别是高盐条件下的氧化(提高量达47.8%)。所有样品经MTG交联后凝胶强度均显著增加(p<0.05),高盐条件下氧化的蛋白其凝胶强度明显高于低盐条件,然而在所有盐浓度下,氧化蛋白的凝胶强度增幅均小于未氧化的。结果表明过多的交联反应反而不利于蛋白成胶性。      

Rheological and Microstructural Properties of Porcine Myofibrillar Protein–Lipid Emulsion Composite Gels

ABSTRACT:  The objective of the study was to investigate the role of emulsified fat (lard) and oil (peanut oil) in the rheology and microstructure of porcine myofibrillar protein (MP) gels. Heat-induced composite gels were prepared from 2% MP with 0% to 15% pre-emulsified lipids at 0.6 M NaCl, pH 6.2. Dynamic rheological testing upon temperature sweeping (20 to 80 °C at 2 °C/min) showed substantial increases in G ' (an elastic modulus) of MP sols/gels with the addition of emulsions. Gel hardness was markedly enhanced ( P < 0.05) by incorporating ≥10% emulsions, and the composite gel with 15% lard was 33% more rigid ( P < 0.05) than that with 15% peanut oil. Incorporation of both emulsions at 10% or higher levels improved the water holding capacity of the gels by 28% to 44% ( P < 0.05). Light microscopy revealed a compact gel structure filled with protein-coated fat/oil globules that interacted with the protein matrix via disulfide bonds. The results indicated that both physical and chemical forces contributed to the enhancements in the rheology, moisture retention, and lipid stabilization in the MP–emulsion composite gels.     

Casein gelation under simultaneous action of transglutaminase and glucono‐δ‐lactone

Casein solutions (5% w/v) were treated with microbial transglutaminase (MTG) and glucono‐δ‐lactone (GDL) under varying conditions in order to obtain gels. Storage modulus (G ′) and gelation time of the gels were measured by oscillation rheometry, while protein cross‐linking was determined by gel permeation chromatography. The addition of only GDL to milk resulted in very weak gels, while MTG on its own was not able to create gel networks. Simultaneous action of both ingredients led to gels, the firmness of which was linearly related to the added amount of MTG, but passed through a maximum with rising GDL concentrations. Using chromatographical analysis, increasing G ′ values were interrelated with the formation of MTG‐induced oligomers. The gelation time was directly proportional to the GDL concentration but not influenced by the addition of MTG within the studied range of concentration.     

基于MP-KG凝胶体系研究微观结构影响质构特性的调控机制

以肌原纤维蛋白-魔芋胶（myofibrillar protein-konjac glucomannan,MP-KG）为模拟体系,利用质构仪、石蜡切片和扫描电镜分别测定复合凝胶质构特性、空间分布和蛋白三维凝胶网络结构,进而阐释复合凝胶微观结构对质构特性的调控机制,为KG在低脂肉制品中的应用提供一定的理论基础。质构特性结果显示：随着KG添加量增高,复合凝胶断裂形变时应力变化呈现抛物线形,说明KG对复合凝胶应力的改善具有添加量极限。复合凝胶断裂形变时应变的变化趋势和应力相似,但是两者的添加量极限不同。低场核磁结果显示：在添加1%KG时不易流动水的弛豫时间最低且其相对百分比最高,分别为274 ms和92.79%,说明KG能够促进蛋白之间的交联,进而提高蛋白基质对水分子的束缚。石蜡切片显示随着KG添加量的提高,MP-KG凝胶体系的空间分布从填充结构转变成互穿结构。扫描电镜显示：对照组的MP凝胶网络结构中布满了相互交错的水沟壑,这些沟壑的存在导致MP凝胶网络结构比较疏松。添加少量KG能够减少蛋白三维网络结构中相互交错的水沟壑,MP凝胶网络结构更加致密均一。添加过量的KG会形成KG连续相,反而破坏蛋...     

不同蜡制玉米淀粉对肌原纤维蛋白凝胶特性的影响

将蜡制玉米淀粉、酯化蜡制玉米淀粉和交联酯化蜡制玉米淀粉以添加量分别为0%、2%、4%、6%、8%、10%添加到肌原纤维蛋白中,形成蛋白淀粉复合物,研究3?种淀粉对肌原纤维蛋白凝胶保水性、质构特性、白度值、表面疏水性、流变特性和微观结构的影响。结果表明,相比纯肌原纤维蛋白,淀粉均能显著提高复合凝胶的保水性、硬度和弹性（P＜0.05）,且随添加量的增加而显著增加（P＜0.05）,但在添加量为10%时,各指标上升不显著（P＞0.05）,其中交联酯化蜡制玉米淀粉效果最好;3?种淀粉均能增加复合凝胶的白度值,但交联酯化蜡制玉米淀粉的添加会使复合凝胶的白度值过大（P＜0.05）,对色泽不利;同时,淀粉能显著提高复合蛋白的表面疏水性和凝胶的弹性模量（P＜0.05）,且随着添加量的增加而显著增加（P＜0.05）,与肌原纤维蛋白凝胶相比,复合凝胶结构趋于致密均匀。在实验的3?种淀粉中,除色泽因素外,交联酯化蜡制玉米淀粉提高凝胶性能的效果要优于其他两种淀粉。?     

Konjac flour improved textural and water retention properties of transglutaminase-mediated,heat-induced porcine myofibrillar protein gel: Effect of salt level and transglutaminase incubation

Functional properties of heat-induced gels prepared from microbial transglutaminase (TG)-treated porcine myofibrillar protein (MP) containing sodium caseinate with or without konjac flour (KF) under various salt concentrations (0.1, 0.3 and 0.6 M NaCl) were evaluated. The mixed MP gels with KF exhibited improved cooking yields at all salt concentrations. TG treatment greatly enhanced gel strength and elasticity (storage modulus, G′) at 0.6 M NaCl, but not at lower salt concentrations. The combination of KF and TG improved the gel strength at 0.1 and 0.3 M NaCl and G′ at all salt concentrations, when compared with non-TG controls. Incubation of MP suspensions (sols) with TG promoted the disappearance of myosin heavy chain and the production of polymers. The TG-treated MP mixed gels had a compact structure, compared to those without TG, and the KF incorporation modified the gel matrix and increased its water-holding capacity. Results from differential scanning calorimetry suggested possible interactions of MP with KF, which may explain the changes in the microstructure of the heat-induced gels.     

磷酸盐-大豆分离蛋白联合处理对草鱼肌原纤维蛋白凝胶化的影响

为探讨磷酸盐(三聚磷酸钠、六偏磷酸钠、焦磷酸钠(tetrasodium pyrophosphate,TSPP))和大豆分离蛋白(soy protein isolate,SPI)对草鱼肌原纤维蛋白凝胶化的影响,采用热处理方法,将不同质量浓度的磷酸盐、SPI与草鱼肌原纤维蛋白混合制成凝胶.用黏度、嫩度、持水性、显微结构和粗...