Myosin denaturation in heated myofibrils of scallop adductor muscle

The thermal inactivation of Ca²⁺ ATPase of scallop myofibrils (0.1 M KCl, pH 7.5) was found to be unaffected by the presence of Ca²⁺. Monomeric myosin content and salt solubility decreased much faster than Ca²⁺ ATPase inactivation in both Ca and EDTA media, which was well explained by faster denaturation of the rod portion than subfragment-1 of myosin. In contrast, when the myofibrils were heated at 0.5 M KCl, a slow decrease in salt solubility was observed, which was also explained by slow denaturation of the rod portion of myosin. Myofibrils from scallop smooth muscle showed the same denaturation pattern as those from adductor muscle. These results show that mollusk myosin is not always stabilized by Ca²⁺.     

Effects of microbial transglutaminase and starch on the thermal gelation of salted squid muscle paste

ABSTRACT:   The addition of microbial transglutaminase (MTGase) to salted squid muscle paste greatly strengthened the elasticity of the thermal gel, which was produced by the preferential cross-linking of myosin heavy chains through a two-step heating process that consisted of setting at 40°C and subsequent heating to 80°C or 90°C. Starch increased the breaking strength of thermal squid gels, but decreased the deformation. Thus, the starch-added gels became harder and less elastic. Although, when both MTGase and starch were added to squid muscle paste, the changes in viscoelastisity and myosin cross-linking reaction were similar to those with MTGase alone during setting, the storage and loss moduli of the paste sharply increased with an increase in starch content above 70°C. Subsequently, the thermal gel texture became more brittle or breakable than gels prepared by setting with MTGase only.     

Thermal gelation behaviors of surimi protein mixed with Hydroxypropylmethylcellulose

ABSTRACT:   This study examined the thermal gelation characteristics of myofibrillar protein (MP) and salt-ground horse mackerel surimi that had been mixed with hydroxypropylmethylcellulose (HPMC). Analysis, using thermal scanning rigidity monitor and differential scanning calorimetry, demonstrated that thermal gelation begins in the thermo-reversible HPMC gel used in this study at approximately 60°C. In the rescanning test, first scanning diagrams showed similar pattern, but second scanning diagrams were rather diverse between MP and MP/HPMC mixture. The addition of HPMC increased rigidity of salt-ground surimi and modified the thermal gelation during the heating process, suggesting that certain enhancing effect of gelation occurred when the mixture of MP and HPMC was heated. In the annealing test, the addition of HPMC lowered the breaking force, but increased the gel strength of surimi due to a substantial increase in deformation. Although the strong cross-linking between the two components might not occur during the gelling process, HPMC gel formed at high temperature occupies some space in thermal gel by interacting with proteins and resulted in a combinative gel with a higher rigidity and gel strength at higher temperature.     

Relationship between the water molecules in fish-meat gel and the gel structure

To elucidate the structure of the network of the water retention mechanism of fish-meat gel, the microscopic relationship between the water content and viscoelasticity was investigated, and the specific surface area (S) where the water molecules are adsorbed was also measured. The gel structures of fish-meat, actomyosin (AM), and myosin (M) were investigated. In the fish-meat gel, as the water content increased, the number of network chains (??) decreased and the molecular weight between the cross-linking points (M _e) increased. At 10?% salinity and approximately 79?% moisture, ?? decreased to a minimum and M _e began to increase remarkably. In addition, when the moisture increased to 78?%, S increased about 1.5 times and the elasticity decreased significantly, indicating that this level of water content is the limit for sufficiently forming a gel structure in fish-meat gel. In the AM and M gels, M _e and S were similar to those observed in the fish-meat gels. When the moisture content increased, they also increased, regardless of the salt concentration. This result suggests that the size of the network was enlarged or that the network chains were cleaved.     

Effect of organic salts on setting gels and their corresponding acids on kamaboko gels prepared from squid Todarodes pacificus mantle muscle

The present study evaluated the quality of setting gels prepared by adding sodium acetate, sodium gluconate, sodium citrate, and sodium succinate to Todarodes pacificus mantle muscle meat, and of the acid-induced kamaboko gels produced by soaking the setting gels in their corresponding acid solutions. The breaking strength was the lowest for the setting gel treated with sodium acetate. The pH values of the acid-induced kamaboko gels decreased when soaked in acid, whereas their moisture contents, whitenesses, and breaking strengths increased. The citric acid-induced kamaboko gel had the highest whiteness index and breaking strength among the gels. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) patterns did not show large differences among the gels, except for a low-intensity polymer band in the gluconic acid-induced kamaboko gel. Sodium citrate combined with citric acid yielded the best-quality acid-induced kamaboko gel among all the combinations, so this condition was used to study the effect of organic salt levels. The breaking strength increased when a sodium citrate level of up to 3% was used for the sodium citrate-treated setting gel, and 10% for the citric acid-induced kamaboko gel. The SDS-PAGE patterns did not differ among the sodium citrate levels. Egg white and microbial transglutaminase were necessary for citric acid-induced kamaboko gel production.     

Contribution of the polymerization of protein by disulfide bonding to increased gel strength of walleye pollack surimi gel with preheating time

ABSTRACT: To clarify the contribution of polymerization of myosin heavy chain (MHC) by disulfide bonding to increased gel strength of cooked gel via preheating, the pastes of walleye pollack surimi (SS and C grades) were preheated at 25°C and 40°C for a variety of hours prior to heating at 80°C for 20 min. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) patterns of cooked gels were analyzed with and without reducing the samples, which were solubilized in 8 M urea–2% SDS solution. The formation of polymers by disulfide bonding in cooked gels was almost constant in each of the SS and C grade surimi gels despite the period of preheating. Therefore, it was suggested that polymerization by disulfide bonding occurred during cooking at 80°C and not during preheating.     

Gel Forming Ability and Other Properties of Eleven Underutilized Tropical Marine Fish Species

Abstract

The gel forming ability and other characteristics of the mince of 11 underutilized marine fish were studied. They were Bombay duck, silverbelly, sea catfish, silver jewfish, jewelled shad, queenfish, Spanish mackerel, hardtail, Indian tuna, tripletail and false conger eel. Mince was prepared from fillet and a portion of the mince was washed two times with cold water (5°C) containing 0.1% NaCl. Both washed and unwashed mince were ground with 3% NaCl. Ground paste was then stuffed into plastic tube and heated for one- and two-step heating. In the one-step heating, the tubes were subjected to 25°, 30°, 35°, 40°, 50°, 60°, 70° and 80°C for 60, 120 and 180 min. In the two-step heating, the tubes were pre-heated at 25°, 30°, 35°, 40°, 50°, 60°, 70° and 80°C for 60, 120 and 180 min. After the pre-heating, the tubes were immediately subjected to 85°C for 30 min. The gel was subjected to puncture, folding, expressible moisture and sensory tests.

Two-step heating distinctly improved the gel strength compared to the one-step heating. The improvement due to two-step heating was more at low preheating temperatures from 25-35°C. Washing improved the texture and color of all of the gels except Bombay duck and decreased the extent of gel-disintegration in silverbelly, queenfish, sea catfish and hardtail. The gels were set optimally at 35°-40°C for most species. Species variation in the disintegration of the gels was observed. Bombay duck mince produced very weak gel. Neither two-step heating nor washing could improve the gel quality of Bombay duck mince. Our data suggested that jewelled shad, queenfish, silver jewfish, sea catfish, tripletail and false conger eel could be suitable as the material for surimi.     

Quality Characteristics of High Pressure-Induced Hake (Merluccius capensis) Protein Gels with and without MTGase

The effects of microbial transglutaminase (MTGase; 0.5%, w/w) and high hydrostatic pressure (HHP) on the quality of protein gels from unwashed mince of hake (Merluccius capensis) trimmings were studied. MTGase incorporation improved texture. Protein solubility was lower for those gels containing MTGase, as a result of myosin heavy chain cross-linking. HHP improved texture. Pressure level was the most important HHP parameter, since higher levels (300 vs. 100 MPa) augmented gel strength (GS). A positive synergistic effect of MTGase and HHP was found for some properties, such as GS, yielding improved gels from a raw material that otherwise shows poor gelation.     

The Effect of Different Types of Fibers on Protein Quality of Crab Leg Analog Paste and Gel Made from Alaska Pollock (Theragra chalcogramma)

The aim of this investigation was to evaluate the effect of wheat, citrus, and carrot fiber on protein oxidation and denaturation of crab leg analog pastes and gels produced from Alaska pollock surimi. There were no significant differences between protein carbonyl contents of the crab leg analog pastes with and without dietary fibers (DF; p > 0.05). The extractability of salt soluble protein in crab leg analog pastes significantly decreased by the addition of DF (p < 0.05), whereas it did not change in the crab leg analog gels (p > 0.05). The electrophoretic patterns in the pastes and gels showed that the addition of carrot fiber followed by wheat fiber and citrus fiber protected the degradation of myosin heavy chains in paste.     

Effect of setting conditions on mechanical properties of acid-induced Kamaboko gel from squid <Emphasis Type="Italic">Todarodes pacificus</Emphasis> mantle muscle meat

Squid Todarodes pacificus suwari gels, set at various temperatures and times, and acid-induced kamaboko gel, which was prepared by soaking suwari gel in 5% acetic acid for 20 h, were studied to evaluate the mechanical properties that are affected by setting conditions. Unset squid meat paste did not form a gel when soaked in acetic acid. The breaking strength of both suwari gel and acid-induced kamaboko gel showed a tendency to increase with setting temperature and time. SDS-PAGE analysis of suwari gel and acid-induced kamaboko gel, which were set at various temperatures and times, showed that myosin heavy chain (MHC) was observed at 30°C only for the first hour. The intensity of the MHC band at 30°C gradually decreased with setting time, while the intensity of the polymer band gradually increased with setting time. These results suggest that the protein-protein bonds in suwari gel affect the final texture of acid-induced kamaboko gel. Based on the analysis of the mechanical properties, and in consideration of the fact that the purpose of this experiment was to reduce energy usage, the best setting condition was determined to be 40°C for 3 h.     

Comparison of Conventional Washing Processing and pH Shift Processing on Gelation Characteristics of Bighead Carp (Aristichthys nobilis) Muscle Proteins

In this study, gelation characteristics of bighead carp (Aristichthys nobilis) protein isolates prepared by pH shift processing were investigated as compared with those of surimi prepared by conventional wash processing. Results showed that the gel from alkali-aided protein isolate exhibited a higher breaking force than that from conventional washed surimi (p < 0.05). However, the gel from conventional washed surimi had higher whiteness (p < 0.05) and lower expressible moisture (p < 0.05). The rheological study showed that protein isolates exhibited different storage modulus and loss tangent patterns from conventional washed surimi during heating. Acid-aided processing could lead to higher denaturation and dissociation for fish muscle myosin and a coarser gel network from the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) pattern and the scanning electron microscopy (SEM). Overall, there is a potential to apply pH shift processing, especially alkali-aided processing, to extract more proteins from bighead carp muscle for the production of surimi-based food.     

Algal biomass accrual in relation to nutrient availability and limitation along a longitudinal gradient of a karst riverine system

Textural property of surimi products is a prime factor in determining the acceptability of consumer as well as market value. Gelatin is one of the most popular biopolymers widely used in food industry as gelling agent with the unique textural properties. Therefore, the addition of gelatin along with the use of protein cross-linkers could be a means to modify the texture of surimi gel, which can fit the demand of consumers. Surimi from the threadfin bream (Nemipterus bleekeri) was added with bovine gelatin (BG) and bovine/fish gelatin mix (BFGM; 1:1, 2:1, 1:2, 4:1, and 1:4) at 10% protein substitution in combination with and without microbial transglutaminase (MTGase) at 1.2 units/g surimi. Textural properties, whiteness, expressible moisture content, protein pattern, and microstructure and sensory properties of gels were determined. When MTGase at 1.2 units/g surimi was incorporated, the increases in breaking force and deformation were noticeable in both surimi gels, with and without 10% BG added ( p < 0.05). On the other hand, surimi gels added with BFGM at all bovine/fish gelatin ratios had the higher breaking force and deformation, compared with that added with BG, when MTGase was incorporated. Addition of BG or BFGM lowered the expressible moisture content and whiteness of surimi gel ( p < 0.05). Based on SDS-PAGE, band intensity of myosin heavy chain and actin of surimi gel decreased when surimi gel was added with all gelatins, regardless of MTGase addition. The microstructure study revealed that surimi gel network became finer and denser with the addition of MTGase (1.2 units/g surimi), but the coarser and irregular structure was obtained when gelatin was incorporated. Gelatin, especially bovine/fish gelatin mix, at an appropriate level could be used as the protein additive in surumi gel in conjunction with MTGase in order to improve the textural and nutritive properties of the products.     

Suppressing effect of neocarrabiose 4-O-sulfate on thermal and freeze denaturation of myosin subfragment-1 and myofibrils

Suppressive effects of neocarrabiose 4-O-sulfate on the thermal and freeze denaturation of myosin subfragment-1 (S-1) and on myofibrils were investigated. The compound strongly suppressed the thermal denaturation of S-1. Its suppressive effect was greater than that of sorbitol and similar to that of maltose. However, it tended to accelerate the denaturation of myofibrils, suggesting a loss of protection by F-actin upon its addition. The compound suppressed the freeze denaturation of myofibrils and S-1. The effect was similar to that of sorbitol or maltose, and completely different from that of Na-sulfate. The compound solubilized myofibrils at concentrations similar to KCl. Therefore, it was concluded that neocarrabiose 4-O-sulfate behaved as an ionic salt in the thermal treatment process, whereas it behaved as a sugar in the frozen storage process.     

Applicability of the modified mooney-rivlin equation on rheological analysis of fish-meat gel

Rheological properties of fish-meat gels were investigated according to the modified Mooney-Rivlin equation and the three-element model representing large and small deformation theories, respectively. The Mooney-Rivlin equation was developed considering directly the volume change with the strain for characterizing rheological property of fish-meat gel. The results led to the conclusion that using the modified large-deformation equation considering volume, changes of samples were more useful to investigate effectively the mechanical behavior of fish-meat gels. The volume changes of fish-meat gel with the, strain resulted that fish-meat gel kept the linearity under about 0.2–0.3 compression strain in stress-strain relation. The stress-relaxation test of fish-meat gel was performed under the strain of 0.25 in the compression process. The elastic moduli and viscosity were decreased with the moisture contents of the gels. These results indicated the same trend as the results according to the modified Mooney-Rivlin equation. Comparing the results according to the large and small deformation theories led to the proportional relationships between the elastic modulus values and the Mooney-Rivlin constants, C ₁ and C ₂.     

Myosin and actin denaturation in frozen stored kuruma prawn Marsupenaeus japonicus myofibrils

Myosin and actin denaturation in kuruma prawn myofibrils stored frozen (0.1 M NaCl, pH 7.5) at ?20 °C was investigated. The inactivation profile of Ca²⁺-ATPase in the myofibrils was identical to that for myosin, indicating that myosin in myofibrils was not protected by actin. The presence of myosin detached from actin in the soluble fraction was proven by ammonium sulfate fractionation in the absence and presence of Mg-ATP. Actin denaturation in myofibrils was further confirmed by its increased susceptibility to chymotryptic degradation. In the frozen myofibrils, actin denatured more rapidly quicker than myosin: actin had completely denatured by storage day 1, followed by a gradual denaturation of myosin. Both myosin and actin in the frozen stored myofibrils retained their high salt-solubility, which decreased slowly during the frozen storage period. The presence of aggregated inactivated myosin in the salt-soluble fraction was proven by precipitation at 40 % saturation of ammonium sulfate in the presence of Mg-ATP, leaving active monomeric myosin in the soluble fraction. Almost no actin denaturation was observed with heated myofibrils.     

Ca2+- and Mg2+-Induced Conformational and Rheological Changes of Actomyosin Extracted from Fresh and Freeze-Thaw Tilapia

ABSTRACT

The conformational changes of natural actomyosins prepared from fresh and freeze-thaw tilapia (Oreochromis niloticus) in the presence of Ca²⁺ or Mg²⁺ were investigated. The Ca²⁺-activated adenosine triphosphatase (Ca²⁺-ATPase) activities of actomyosins extracted from fresh and freeze-thaw fish were comparable (p > 0.05). The denaturation temperatures (T_d) of actomyosins extracted from fresh fish were lower than those from freeze-thaw counterparts (p < 0.05). The addition of Ca²⁺ or Mg²⁺ reduced the T_d of actomyosins. Ca²⁺ and Mg²⁺ enhanced protein aggregation at ≥ 40°C (p < 0.05). Based on the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) pattern, the myosin heavy chain (MHC) and actin bands tended to form large aggregates to a greater extent in the presence of 100mM Ca²⁺ or Mg²⁺. Ca²⁺ and Mg²⁺enhanced disulfide linkages and hydrophobic interactions among actomyosin molecules. The onset temperature of elastic modulus (G′) of both actomyosins was shifted to lower temperature as 100mM of Ca²⁺ or Mg²⁺ was added. Mg²⁺ at 20mM increased the breaking force of washed tilapia mince at 40°C. Our results revealed that the intrinsic properties of actomyosins extracted from fresh and frozen fish were distinct, and divalent ions Ca²⁺ or Mg²⁺ affected their gelation differently.     

Effect of pH on the gelation of walleye pollack surimi and carp actomyosin pastes

ABSTRACT: The effect of pH on thermal gelation and transglutaminase (TGase; EC2.3.2.13)-induced suwari (setting) of surimi and actomyosin pastes was investigated. A strong and elastic gel was produced from walleye pollack surimi paste at pH 7.0 in the presence of Ca²⁺ using a two-step heating method. In contrast, walleye pollack actomyosin paste formed a weak gel under the same conditions as a result of the low concentration of endogenous TGase. In the presence of EGTA [ethyleneglycol bis(2-aminoethylether) tetraacetic acid], weak gels were formed at pH values of 7.0 and 6.0. Non-proteolytic modori (gel weakening) occurred extensively in the course of actomyosin gelation, but not in surimi gelation. Maximum TGase-induced myosin heavy chain cross-linking was observed at a slightly higher pH of 7.5 than at the optimal pH of endogenous TGase activity; the difference being derived from different substrates. Gelation of carp actomyosin paste at pH values of 5.5, 6.0, 6.5 and 7.0 was monitored by measuring storage modulus (G') and loss modulus (G"). A weak gel was formed at all pH values, but a slightly rigid and less elastic gel was obtained at lower pH values. The addition of microbial TGase (MTGase) formed strong elastic gels at pH 7.0 and 6.5. MTGase cross-linked myosin heavy chains even at pH 5.5, but contributed neither to suwari response nor strong gel formation. Overall, results suggest that the optimal pH for the gelation of surimi paste from easy-setting fish species is a compromise between the pH-optima of TGase activity and of preferable actomyosin conformation for myosin cross-linking.     

Physicochemical and Gel Properties of Myofibrillar Protein from Sin Croaker (Johnius dussumieri) Fish During Ice Storage

The physicochemical and gel properties of myofibrillar protein (MFP) from sin croaker fish were studied during ice storage for 18 days. Significant changes in the trends of solubility, Ca²⁺ ATPase enzyme activity, surface hydrophobicity, and water holding capacity of extracted MFP were observed by the 6th day of storage. The Ca²⁺ ATPase enzyme activity reduced significantly (p < 0.05) by the 6th day of storage. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) did not show a remarkable change in the concentration of myosin heavy chain. Surface hydrophobicity increased almost four times from its original value of 18.98 µg; whereas, water holding capacity showed a fluctuating trend during storage. The emulsion capacity of the MFP was in the range of 0.89- to 1.92-mL oil/mg protein during storage. The gel strength value (313.45 g.cm) of heat-induced gel prepared from fresh minced meat decreased significantly (p < 0.05) by the 6th day of ice storage. Texture profile analysis revealed that changes in hardness and gumminess were concurrent to steeply reducing breaking force up to the 6th day. The histological observation showed gradually increasing gaps between muscle fibers. The histological observations and physicochemical quality indicated that the sin croaker fish can be used for producing good quality surimi when stored for up to 6 days in ice.     

Improvement of Cold and Thermally Induced Gelation of Giant Squid (Dosidicus gigas) Surimi

Depending on the season of capture, giant squid (Dosidicus gigas) surimi processed by isoelectric precipitation presents low gel strength. Addition of microbial transglutaminase (MTGase) and application of high isostatic pressure (300 MPa) to improve physicochemical properties were assayed for purposes of making “suwari” gels and heated gels for use in restructured products which have a raw or cooked appearance. The physicochemical properties of both pressurized and unpressurized gels induced by application of 30°C/1 h improved when MTGase was added. In contrast, addition of MTGase was less effective in gels subsequently heated at 90°C/30 min after 30°C/1 h. High pressure treatment for 30 min at 300 MPa and 15°C helped to produce gels with better mechanical and water binding properties, whether treated for 30°C/1 h only or for 30°C/1 h plus 30-min heat treatment at 90°C. High pressure treatment also reduced lightness.     

Comparative study on thermal denaturation modes of myosin in walleye pollack and carp myofibrils as affected by salt concentration

ABSTRACT:   The effect of salt concentration on the thermal denaturation profile of myosin in walleye pollack and carp myofibrils was compared by studying the subfragment-1 (S-1) and rod denaturation rates upon heating. Species-specific denaturation mode observed at 0.1 M KCl was no longer detected when samples were heated above 0.5 M KCl, where S-1 and rod denaturation rates were identical to each other. As the heating of the chymotryptic digest of myofibril formed practically no rod aggregates, S-1 denaturation in a form of myosin was the rate limiting step for rod aggregate formation. As the aggregate formation by rod was remarkably suppressed by lowering the temperature, the free movement of myosin tail upon heating was suggested to play an important role in the rod aggregate formation in a high salt medium.