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.     

Combined Effect of High Hydrostatic Pressure and Lysine or Cystine Addition in Low-Grade Surimi Gelation with Low Salt Content

The aim of this study was to reduce the sodium chloride (NaCl) level in surimi-based products by adding lysine or cystine in combination with high hydrostatic pressure (HHP). For experiments, Alaska pollock surimi was used to prepare gels in a factorial design (3?×?3?×?2) using three additive levels (no additive, lysine, and cystine), three NaCl levels (0, 0.3, and 3 %), and two HHP levels (0 and 300 MPa/10 min/10 °C). After blending, the pastes, consisting of surimi, additives, and different levels of salt, were stuffed into casings, high pressure treated, and stored at 5 °C for 24 h (suwari gel). Subsequently, samples were heated at 90 °C for 30 min (kamaboko-type gel). To assess the degree of protein denaturation prior to gelation at 90 °C, suwari gels were analyzed by differential scanning calorimetry to determine myosin denaturation enthalpy. Kamaboko-type gels were characterized by lightness properties, water binding capacity, and mechanical properties (by puncture test). Results showed that the pressure treatment at 300 MPa and/or the addition of lysine or cystine (0 and 0.1 %) to low-sodium-chloride samples (0 and 0.3 %) resulted in gels with similar quality characteristics to those with the regular 3 % sodium chloride addition, most likely due to the protein unfolding induced by both HHP treatment and the additives used.     

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.     

Microbial Transglutaminase and Recombinant Cystatin Effects on Improving the Quality of Mackerel Surimi

ABSTRACT: Effects of microbial transglutaminase (MTGase), recombinant cystatin, or their combination on the gel properties of mackerel surimi were investigated. The addition of MTGase caused the cross-linking of myosin heavy chain (MHC) and substantially increased the gel strength (from 536.6 to 2012.4 g × cm), while the recombinant cystatin could effectively prevent the MHC degradation and gel softening during the production of mackerel surimi-based products. Combined use of MTGase and recombinant cystatin revealed synergistic effectiveness on improving the quality of mackerel surimi (increased from 435 to 2438 g × cm, set at 45 °C for 20 min).     

Transglutaminase Effects on Low Temperature Gelation of Fish Protein Sols

Myosin polymerization and formation of ?-(γ-glutamyl)lysine linkages were quantified in Alaska pollock surimi gels which contained no additive (control), or a commercial microbial transglutaminase (MTGase). As preincubation (“setting”) time at 25°C was increased, the gel strength of control and 0.2% MTGase-added samples increased, with greater increases at higher MTGase levels. SDS-PAGE and HPLC analyses showed increasing nondisulfide polymerization and ?-(γ-glutamyl)lysine dipeptide content, with increasing setting time and/or added MTGase. Content of ?-(γ-glutamyl)lysine dipeptide correlated with gel strength (shear stress) and shear modulus at failure (G_f) for these gels. Higher stresses were measured in samples containing 0.2% MTGase than in controls at corresponding levels of ?-(γ-glutamyl)lysine dipeptide, indicating that rate of myosin polymerization may affect ultimate gel strength.     

鸡蛋清蛋白对微生物转谷氨酰胺酶诱导鲢鱼鱼糜凝胶形成的影响

通过对鲢鱼鱼糜凝胶特性和溶解率的测定及SDS-PAGE检测研究鸡蛋清蛋白改善鱼糜凝胶特性的机理及其对微生物转谷氨酰胺酶(MTGase)诱导鱼糜凝胶形成的影响。结果表明：鸡蛋清蛋白(EA)和MTGase均能显著提高鱼糜凝胶特性。EA会降低MTGase诱导鱼糜凝胶的形成,显著降低MTGase诱导鱼糜凝胶的凝胶强度和破断强度,但不阻碍MTGase对肌球蛋白重链(MHC)的交联。     

Modification in physical properties of rice gel by microbial transglutaminase

BACKGROUND: Microbial transglutaminase (MTGase) may catalyse the cross‐linking between a peptide‐bound glutaminyl residue and an ε‐amino group of lysine residue in protein. MTGase has been used to modify many food proteins for improving the physical properties of products. However, its effect on the physical properties of rice products has not been investigated before. The present study aimed to investigate the effect of MTGase, as an additive in rice flour, on the rheological, textural and thermal properties of rice gel. RESULTS: Both the elastic and the viscous moduli of rice gel were increased as a result of the addition of MTGase to rice flour. The addition of MTGase at 0.01–0.3 U mg^?1 increased textural parameters (hardness and gumminess) and rheological properties. Differential scanning calorimetry also showed that MTGase treatment decreased the enthalpy change in gelation. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) confirmed that rice proteins were polymerised through the MTGase reaction. CONCLUSION: The present study proved that the cross‐linking of protein molecules in rice flour by the action of MTGase may improve the physical properties of rice gel. The addition of MTGase in rice flour in an adequate amount is essential for achieving appropriate physical properties of the product. Copyright © 2008 Society of Chemical Industry     

Comparison of Atlantic menhaden gels from surimi processed by acid or alkaline solubilization

Heat-induced gelling abilities of surimis prepared by pH shifting (isoelectric precipitation following acid (AC) or alkaline (AL) solubilization) were compared to that of conventionally washed (CW) surimi. Greater endogenous transglutaminase activity (evidenced as enhanced strength of cooked gels subjected to 30–40 °C preincubation) was measured for CW and AL surimi than for AC surimi (all at pH 7). Upon addition of microbial transglutaminase (MTGase), increased crosslinking of myosin heavy chain and gel strengthening during 30–40 °C preincubation were apparent for all three types of surimi, most markedly in CW and AL surimi. Salt addition improved CW gels most, but seemed to adversely affect MTGase activity in AC and AL surimi. AC and AL surimi gels were of lower whiteness than were CW surimi gels.     

Microbial Transglutaminase Affects Gel Properties of Golden Threadfin-bream and Pollack Surimi

ABSTRACT: The properties of surimi gels from threadfin-bream and pollack surimi set at 30 °C or 45 °C with microbial transglutaminase (MTGase) from Streptoverticillium ladakanum were determined. The optimal amounts of MTGase and setting conditions were: 0.3 unit/g surimi either at 30 °C for 90 min or at 45 °C for 20 min for threadfin-bream, and 0.2 unit/g surimi at 30 °C for 60 min for pollack. The strength of golden threadfin-bream surimi gels with 0.35 unit MTGase set at 30 °C for 90 min or 45 °C for 20 min was 3400 g cm, almost 3-fold of the control. SDS-PAGE analyses indicated that inter- and/or intramolecular cross-linking formed in the myosin heavy chain of MTGase-containing surimi gels.     

Improvement of Hairtail Surimi Gel Properties by NADPH-Sulfite Reductase, Recombinant Cystatin, and Microbial Transglutaminase

ABSTRACT: Effects of nicotinamide dinucleotide phosphate (NADPH)-sulfite reductase, recombinant cystatin, and microbial transglutaminase (MTGase) or their combination on hairtail surimi quality were investigated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that adding NADPH-sulfite reductase could effectively recover native myosin. Apparent cross-linking of hairtail myosin during the setting process was observed with added MTGase, while myosin degradation on the heating process was substantially retarded with recombinant chicken cystatin. The combined use of NADPH-sulfite reductase, recombinant chicken cystatin, and MTGase exhibited a greater effect on improving hairtail surimi quality.     

Protein Oxidation at Different Salt Concentrations Affects the Cross‐Linking and Gelation of Pork Myofibrillar Protein Catalyzed by Microbial Transglutaminase

In a fabricated then restructured meat product, protein gelation plays an essential role in producing desirable binding and fat‐immobilization properties. In the present study, myofibrillar protein (MFP) suspended in 0.15, 0.45, and 0.6 M NaCl was subjected to hydroxyl radical stress for 2 or 24 h and then treated with microbial transglutaminase (MTGase) in 0.6 M NaCl (E : S = 1 : 20) at 4 and 15 °C for 2 h. Protein cross‐linking and dynamic rheological tests were performed to assess the efficacy of MTGase for mediating the gelation of oxidized MFP. MTGase treatments affected more remarkable polymerization of myosin in oxidized MFP than in nonoxidized, especially for samples oxidized at 0.6 M NaCl. Notably, the extent of MTGase‐induced myosin cross‐linking at 15 °C in oxidized MFP improved up to 46.8%, compared to 31.6% in nonoxidized MFP. MTGase treatment at 4 °C for MFP oxidized in 0.6 M NaCl, but not MFP oxidized in 0.15 M NaCl, produced stronger gels than nonoxidized MFP (P < 0.05). The final (75 °C) storage modulus (G′) of oxidized MFP gels was significantly greater than that of nonoxidized, although the G′ of the transient peak (～44.5 °C) showed the opposite trend. Overall, oxidation at high salt concentrations significantly improved MTGase‐mediated myosin cross‐linking and MFP gelation. This might be because under this condition, MTGase had an increased accessibility to glutamine and lysine residues to effectively initiate protein–protein interactions and gel network formation.     

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     

CHITOSAN AFFECTS TRANSGLUTAMINASE-INDUCED SURIMI GELATION

Effect of chitosan on barred garfish (Hemiramphus far) surimi gel was studied in the presence of EDTA and microbial transglutaminase (MTGase). An increase in breaking force of surimi gels added with 1.0% prawn shell chitosan indicated the gel enhancing effect of chitosan on the heat‐induced gelation of fish myofibrillar proteins. However, gel‐forming ability of surimi containing chitosan was inhibited in the presence of EDTA, especially at higher concentration. Therefore, the enhancing effect of chitosan was possibly mediated through the action of endogenous transglutaminase (TGase) during setting, resulting in the formation of protein‐protein and protein‐chitosan conjugates. In general, addition of MTGase remarkably increased both breaking force and deformation of surimi gel (P<0.05). However, enhancing effect of MTGase was retarded in the presence of chitosan, resulting in lower magnitude of breaking force and deformation (P<0.05). Scanning electron microscopy showed that chitosan particles were uniformly dispersed in the gel matrix. A tightly associated gel network was formed in surimi containing MTGase, whereas a large number of voids were noted in gels with EDTA. These results suggest that chitosan acted as a surimi gel enhancer in combination with endogenous TGase in fish muscle, but hindered gel formation in the presence of MTGase.     

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.     

DIFFERENT ARRANGEMENT OF ɛ-(γ-GLUTAMYL)LYSINE CROSS-LINKING IN ALASKA POLLOCK (THERAGRA CHALCOGRAMMA) SURIMI PROTEINS BY STREPTOVERTICILLIUM AND ENDOGENOUS TRANSGLUTAMINASES DURING SUWARI PROCESS

The objective of the present study is to compare the protein cross‐linking reaction in Alaska pollock surimi that is catalyzed by a commercially available microbial transglutaminase and by endogenous Alaska pollock transglutaminase. The endogenous transglutaminase was inhibited by EGTA and activated by CaCl₂ The microbial transglutaminase was added to the salted surimi with and without EGTA and CaCl₂. These surimi pastes were incubated at 25C up to 24 h followed by cooking at 90C. The resultant gels were fractionated into soluble and insoluble (aggregate) fractions by SDS‐urea extraction. Compositional analysis revealed that the aggregate consisted predominantly of cross‐linked myosin heavy chain. The distribution of ?‐(γ‐glutamyl)lysine isopeptide in the soluble and aggregate fractions andpeptide mapping analyses of the aggregate fraction demonstrate that the formation of isopeptide cross‐links in Alaska pollock surimi proteins during suwari process differs when catalyzed by the microbial transglutaminase and endogenous transglutaminase.     

Gelation of Food Protein Induced by Recombinant Microbial Transglutaminase

ABSTRACT: The recombinant microbial transglutaminase from Streptoverticillium mobaraense var. (rMTGase) was expressed in Escherichia coli. Specific enzyme activity of rMTGase was comparable to native MTGase. However, the gelation of a sodium caseinate solution induced by rMTGase was slower than that induced by native MTGase. In addition, the mechanical property of kamaboko prepared with rMTGase was weaker than that with native MTGase. In SDS‐PAGE analysis, α‐casein monomers decreased more slowly during the incubation with rMTGase than MTGase. These results confirmed the difference of cross‐linking activity between the 2 enzymes. Furthermore, thermal stability of rMTGase was lower compared to native MTGase. These results suggest that the difference of cross‐linking activity and thermal stability between the 2 enzymes cause differences in gelation activity of protein.     

Surimi gels from striped mullet (Mugil cephalus) employing microbial transglutaminase

Striped mullet (Mugil cephalus) is an abundant marine coastal fish of tropical waters and has a low commercial value. This work deals with the assessment of striped mullet as a resource for surimi gels. To improve the gels obtained, the addition of microbial transglutaminase was evaluated. Optimal conditions for setting were determined using mathematical models. Concentration of microbial transglutaminase (MTGase), temperature and time were studied to improve the mechanical properties of surimi gels from striped mullet. Shear stress was strongly affected by the variables studied while shear strain was moderately affected. Maximum shear stress (156 kPa) was obtained by employing the following setting conditions: a concentration of MTGase of 9.3 g/kg of surimi, a temperature of 37°C and a time of 3.9 h. Under these conditions the shear strain was 1.34. Maximum shear strain (1.57) was obtained by employing the following conditions: a concentration of MTGase of 5 g/kg of surimi, a temperature of 34.5°C and a time of 1 h. Under these conditions the shear stress was 123 kPa.     

大豆分离蛋白对微生物转谷氨胺酶诱导鲢鱼糜凝胶形成的影响

本实验通过对鲢鱼糜凝胶特性和溶解率的测定及SDS-PAGE、扫描电镜观察,研究大豆分离蛋白(SPI)对微生物转谷氨酰胺酶(MTGase)诱导鱼糜凝胶形成的影响及作用机理。结果表明：SPI 和MTGase 均能显著提高鱼糜凝胶特性,但SPI 的添加会阻碍MTGase 对肌球蛋白重链(MHC)的交联,降低鱼糜凝胶特性,增加溶解率。SPI改善鲢鱼糜凝胶特性的机理是自身的凝胶作用和抑制蛋白酶活性。     

Effect of dietary fibre and MTGase on the quality of mackerel surimi gels

BACKGROUND: The effects of microbial transglutaminase (MTGase; 5 g kg^?1) and dietary fibre (inner pea fibre and chicory root inulin, 20 and 40 g kg^?1) on gels from surimi made with Atlantic (Scomber scombrus) and chub mackerel (Scomber japonicus) were studied with the purpose of achieving a better understanding of the underlying phenomena and improving gels. RESULTS: MTGase addition improved textural properties (namely, cohesiveness increased from 0.19–0.41 to 0.59–0.72) and increased pH and water‐holding capacity (WHC). Moreover, MTGase reduced the elastic and viscous modules and darkened gels; protein solubility declined, meaning greater protein aggregation, according to electropherograms. MTGase had no unequivocal effect upon the gels' microstructure. Pea fibre increased hardness (an increase of almost 60% with 40 g kg^?1) and related parameters, the elastic and viscous modules and WHC. Pea fibre reduced extractable protein in sodium dodecyl sulfate and urea (in the absence of MTGase) as well. Scanning electron microscopy revealed different structures for gels containing pea fibre. Regarding inulin, it worsened textural quality and WHC. CONCLUSION: A combination of MTGase and pea fibre can improve a poor quality surimi. Copyright © 2009 Society of Chemical Industry     

Combination Effects of Microbial Transglutaminase, Reducing Agent, and Protease Inhibitor on the Quality of Hairtail Surimi

A combination of microbial transglutaminase (MTGase), reducing agent and protease inhibitor was employed to improve the quality of underutilized fish surimi. SDS-PAGE indicated that cross-linking of myosin heavy chain (MHC) occurred in MTGase-contained samples, while MHC of samples without MTGase disappeared after 120 min incubation at 45°C. Although the gel-forming ability increased with MTGase added up to 0.6 unit/g, it was still too low to be commercially acceptable. However, the combined use of 0.1% NaHSO₃, 0.01 mM transepoxysuccinyl-L-leucylamido-(4-guanidino)butane (E-64) and 0.35 units MTGase/g substantially improved the quality of hairtail surimi. Based on this result, the combined use of E-64, MTGase and NaHSO₃ seemed to be a better way to improve gel-forming ability of hairtail surimi.