Thermal Gel Degradation (Modori) in Sturgeon (Acipenseridae) Surimi Gels

Sturgeon meat has been found to be suitable as surimi raw materials. The present study determined the modori phenomenon in sturgeon surimi gels and identified its relationship with cathepsins. In all heat‐treated gels (25 to 90 °C, at 5 °C intervals), the 40 °C‐incubated sturgeon surimi gel showed the weakest gel properties and water‐holding capacity (P < 0.05), a rough protein gel network under SEM, and the highest protein solubility and trichloroacetic acid‐soluble peptides content (P < 0.05). SDS‐PAGE indicated that the myosin heavy chain band of sturgeon surimi gels was almost completely degraded at 40 °C. Moreover, the highest cathepsin L activity was observed in 40 °C‐treated sturgeon surimi gels (P < 0.05). Our results suggested that the modori phenomenon in sturgeon surimi gels occurred at 40 °C, which was partially attributed to cathepsin L, thereby allowing for the better exploitation and utilization of sturgeon surimi.     

Effect of microbial transglutaminase on autolysis and gelation of lizardfish surimi

In the absence of microbial transglutaminase (MTGase), the textural properties of lizardfish surimi (Saurida spp) improved when pre‐incubated at 4 and 25 °C for 24 and 4 h, respectively. MTGase optimally catalyzed incorporation of monodansylcadaverine (MDC) into surimi at 40 °C. Addition of MTGase appeared to reduce autolytic activity at 25 and 40 °C, but had no effect on autolytic activity at 65 °C. Breaking force and deformation of lizardfish surimi significantly improved when 0.1 unit MTGase g^?1 surimi (1.8 g kg^?1) was added and pre‐incubated at either 25 or 40 °C. Textural properties improved concomitant with cross‐linked polymers of myosin heavy chain and tropomyosin, but not actin. Addition of MTGase also improved the storage modulus (G′). The gel network of surimi mixed with MTGase and pre‐incubated at 40 °C readily formed during the pre‐incubation period, while formation of the gel network began at 48.1 °C in the absence of MTGase. Copyright © 2005 Society of Chemical Industry     

High Pressure Effects on Gelation of Surimi and Turkey Breast Muscle Enhanced by Microbial Transglutaminase

High pressure effects on the strength (stress) and elasticity/deformability (strain) of surimi and turkey breast meat gels containing microbial transglutaminase (TGase) were evaluated. Pressurization of muscle proteins at 4°C prior to incubation at 25°C or 40°C (setting) increased gel strength 2–3 fold in uncooked surimi gels, but not in uncooked turkey gels. However, pressurization at 40°C or 50°C prior to setting increased the strength of turkey gels. Similar effects of prior pressurization, but of lesser magnitude, occurred in gels formed by directly or subsequently (following setting) cooking at 90°C. SDS-PAGE confirmed that myosin crosslinking occurred due to TGase activity during the setting treatment, which had survived prior pressure treatment. High pressure rendered protein substrates more accessible to TGase thereby enhancing intermolecular cross-link formation and gel strength.     

Original article: Gel properties of red tilapia surimi: effects of setting condition,fish freshness and frozen storage

This study aimed to determine effects of setting condition, fish freshness and storage time of frozen surimi on properties of red tilapia surimi gel. To investigate the effect of setting condition, a combination of eight setting temperatures (35–70 °C) and four setting times (30–120 min) was used. Maximum breaking force, deformation and gel strength were obtained after the gel had been set at 40 °C for 90 or 120 min. Setting at 65 °C resulted in the lowest obtained gel strength, because of proteolytic degradation of myosin heavy chain. Increasing storage time of raw fish material in ice caused a significant decrease in gel strength of the resultant surimi gel (P < 0.05). Gels produced from surimi kept in frozen storage for up to 9 months also exhibited reduced gel strength, with a concomitant increase in the expressible drip, with increasing storage time (P < 0.05).     

Gelation of Beef Heart Surimi as Affected by Antioxidants

Oxidation of proteins (carbonyls) and lipids (TBARS) in beef heart surimi-like materials during preparation and storage (2°C) was inhibited by propyl gallate (0.02%) or α-tocopherol (0.2%). Inhibition of oxidation did not affect surimi gel property (storage modulus, G'). Storage promoted oxidation of proteins in 0.2% ascorbate-washed mince, leading to increases in peak (～ 55°C) and final (70°C) G' of thermally induced surimi gel. Protein carbonyls in stored surimi and its sol (salted), as well as TBARS of the sol, strongly correlated with both peak and final G of gels. Incorporation of tripolyphosphate into washed mince promoted gelation whether the surimi-like material was oxidized or not.     

Proteinase inhibitory activity of sarcoplasmic proteins from threadfin bream (Nemipterus spp.)

BACKGROUND: Thailand is the second largest surimi producer in the world and 50% of surimi is produced from threadfin bream. During surimi processing, sarcoplasmic proteins are removed through water washing and discarded in the waste stream. This study was aimed at investigating the proteinase inhibitory activity of sarcoplasmic proteins. RESULTS: Sarcoplasmic proteins from threadfin bream (TBSP) exhibited inhibitory activity toward trypsin but did not inhibit papain and chymotrypsin. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis under non‐reducing condition stained by trypsin inhibitory activity revealed three protein bands of molecular mass of 95, 41 and 37 kDa. Inhibitory activity of TBSP reached a maximum when subjected to 45 °C and completely disappeared at 60 °C. The breaking force and deformation of lizardfish surimi gel with added TBSP and pre‐incubated at 37° for 20 min increased with additional levels of TBSP (P < 0.05). Trichloroacetic acid–oligopeptide content of lizardfish surimi gel with added TBSP decreased with the addition of 4 g kg^?1 TBSP (P < 0.05). Retention of myosin heavy chain (MHC) increased when TBSP concentration was increased. TBSP effectively protected MHC from proteolysis at 37 °C to a similar extent as egg white powder, but efficacy of TBSP was not observed at 65 °C. CONCLUSION: TBSP could be applied to reduce proteolytic degradation of lizardfish surimi or other surimi associated with trypsin‐like proteinase, rendering an improvement in surimi gelation set at 37–40 °C. Copyright © 2009 Society of Chemical Industry     

Trypsin Inhibitory Activity and Gel‐Enhancing Effect of Sarcoplasmic Proteins from Common Carp

Abstract: Proteinase inhibitory activity of sarcoplasmic protein (SP) extracted from common carp (Cyprinus carpio) muscle and its gel‐improving ability were investigated. SPs displayed 89% and 54% inhibitory activity toward trypsin at 40 and 65 °C, respectively. Protein bands with molecular mass of 69, 50, 44, 41, and 35 kDa appeared on trypsin inhibitory activity staining under nonreducing condition when incubated at 40 °C, while 2 protein bands at 54 and 35 kDa were observed at 65 °C. Addition of SP at 0.18 g protein/100 g increased textural properties of threadfin bream surimi gel. However, when SP was added in combination with various CaCl₂ concentrations (0.1% to 0.5%) it did not further improve textural properties as compared to the addition of SP alone. Retention of myosin heavy chain of threadfin bream surimi was greater with the addition of SP. These results indicated that the gel‐enhancing effect of common carp SP was due to the inhibitory activity toward endogenous trypsin‐like proteinases in threadfin bream surimi. Practical Application: Sarcoplasmic protein from common carp muscle could be used as a functional protein ingredient that minimizes muscle proteolysis and improves textural properties of surimi containing trypsin‐like endogenous proteinases.     

漂洗前后四大家鱼鱼糜品质的变化

以鲜活四大家鱼为原料,结合鱼糜工业漂洗方法,对四大家鱼鱼糜漂洗前后的组织蛋白酶B、H、L的活性及pH值、凝胶强度、折叠柔韧性、持水性能和白度值进行研究。结果表明：四大家鱼鱼糜经过漂洗后,鱼糜质量得到了显著改善,其凝胶强度、折叠柔韧性、持水性能以及白度值均显著上升;而组织蛋白酶B、H、L活性均显著下降,其中组织蛋白酶H几乎被完全漂洗去除,组织蛋白酶B、L的残留率较大,四大家鱼凝胶强度及持水性大小顺序依次均为：青鱼＞鲢鱼＞鳙鱼＞草鱼。     

Purification and Characterization of Low Molecular Weight Kininogen from Pig Plasma

A cysteine proteinase inhibitor from pig plasma with a molecular weight (MW) of 55 kDa, purified to electrophoretical homogeneity, inhibited μ- and m -calpains, cathepsins B, L, and L-like, and papain, but did not inhibit trypsin, β-chymotrypsin, and cathepsin D. The purified inhibitor was stable at pH 3.0 to 10.5. The amounts for 50% inactivation (ID₅₀) of papain, cathepsins B, L, and L-like, μ- and m-calpains were 10.55, 12.91, 2.18, 2.18, 30.91, and 29.27 nM, while the inhibition constant (K_i) for cathepsins B, L, L-like, and X, and μ- and m-calpains were 1.1, 0.64, 63.33, 8.19, 26, and 23.57 nM, respectively. It could inhibit the proteolysis of mackerel myosin heavy chain caused by purified cathepsin L-like at 55 °C. Based on the MW, stability and specificity, it was identified as L-kininogen.     

Cathepsin Degradation of Pacific Whiting Surimi Proteins

Cathepsin B was the most active cysteine protease in Pacific whiting fish fillets; cathepsin L was predominant in surimi. Cathepsin L showed highest activity at 55°C in both fish fillets and surimi, indicating its function in myosin degradation during conventional heating of fillets and surimi, gels. Washing during surimi processing removed cathepsin B and H but not cathepsin L. Myosin heavy chain was the primary substrate during autolysis of surimi paste and actin and myosin light chain showed limited hydrolysis during 2 hr incubation. Purified Pacific whiting cathepsin L hydrolyzed myofibrils, myosin and native and heat-denatured collagen. The degradation pattern of myofibrils by the protease was the same as the autolytic pattern of surimi.     

Effect of soy protein isolate on gel properties of Alaska pollock and common carp surimi at different setting conditions

The effects of soy protein isolate (SPI) on the gel properties of different grade Alaska pollock and common carp surimi at different setting conditions were evaluated and compared. Breaking force and distance of gels decreased with increasing SPI concentrations in direct cook (85 °C for 30 min) and in cook after setting at 30 °C for 60 min conditions. The effect of SPI on gel strength of common carp surimi was less than in Alaska pollock surimi. The breaking force obtained for addition of 10% SPI to Alaska pollock surimi was higher than for surimi alone when cooked after incubation at 50 °C for 60 min. Addition of SPI decreased the whiteness and increased the yellowness of the gel. The gel structure showed that the addition of SPI modified the microstructure of the fish protein gel, thus resulting in surimi with different gelling properties. Copyright © 2004 Society of Chemical Industry     

Isolation of cathepsin B from the muscle of silver carp (Hypophthalmichthys molitrix) and comparison of cathepsins B and L actions on surimi gel softening

Cathepsin B from silver carp muscle was purified to 263-fold by acid treatment, ammonium sulfate fractionation, followed by a series of chromatographic separations. The molecular mass of the purified enzyme was 29 kDa as determined by SDS-PAGE and immunoblotting. The purified enzyme was activated by dithiothreitol and cysteine while it was substantially inhibited by E-64, suggesting the purified enzyme belongs to the cysteine proteinase family. Optimal pH and temperature were 5.5 and 35 °C, respectively. The enzyme catalyzed the hydrolysis of Z-Arg-Arg-MCA with a parameter of K_m (90 μM) and K_cat (20.3 s⁻¹), but hardly hydrolyzed Arg-MCA. Analysis of surimi gel strength and microstructure showed that cathepsins B and L were capable of destroying the network structure of silver carp surimi gels, consequently causing gel softening. Cathepsin L might play an important role in the modori effect.     

Sardine Surimi Gels as Affected by Salt Concentration, Blending, Heat Treatment and Moisture

The effects of simultaneous modification of salt concentration, blending time, moisture content and heat treatment at different setting and cooking temperatures and time on characteristics of sardine (Surdina pilchardus) surimi gels was examined using a randomized incomplete block design. Maximum gel strength (GS) was obtained at highest salt concentrations and 78% moisture. Pre-setting was required to achieve acceptable gel quality. Highest GS values were found in gels set for 30–60 min at 35°C prior to heating at 90°C for 40 min. However, GS decreased after prolonged heating at 90°C. Gels set at 25, 35 and 40°C for 90 min had lower GS values when heated at 90°C for 40 min but were stable during further heating.     

Participation of cysteine protease cathepsin L in the gel disintegration of red bulleye (Priacanthus macracanthus) surimi gel paste

BACKGROUND: Endogenous proteases, among them cysteine‐type proteases, are reported to contribute to gel disintegration, resulting in kamaboko of poor quality. Severe gel disintegration occurs in red bulleye surimi gel paste. The objective of this study was to clarify the participation of cysteine protease cathepsin L in the gel disintegration of red bulleye surimi. The surimi was made into kamaboko with and without cathepsin L inhibitors. To confirm its hydrolysis action, crude cathepsin L was also extracted and added to the surimi to make kamaboko. RESULTS: The gel strength of kamaboko obtained by both one‐step (50 °C, 2 h) and two‐step (50 °C, 2 h + 80 °C, 20 min) heating was very low in the absence of inhibitors. Protease inhibitors E‐64 and leupeptin were found to enhance the gel strength considerably. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the hydrolysis of kamaboko was promoted by crude cathepsin L and inhibited by E‐64 and leupeptin. The gel strength of two‐step heated kamaboko was increased from 12 to 110 and 130 g cm^?2 by E‐64 and leupeptin respectively at a concentration of 0.2 g kg^?1 surimi. CONCLUSION: Endogenous cathepsin L of red bulleye surimi participates in gel disintegration during kamaboko processing. It does so by degrading the myosin heavy chain of actomyosin and consequently hindering the gelation of red bulleye surimi. Copyright © 2009 Society of Chemical Industry     

Rheological Characteristics of Fibrinogen-Thrombin Solution and Its Effects on Surimi Gels

Gel enhancing effects of fibrinogen-thrombin on surimi were investigated using failure stress and analyzed by mixture design. Gelation time of fibrinogen-thrombin mixture (20:1) gradually decreased as temperature increased from 5 to 40°C, whereas the G′ and G″ values continued to decrease up to 30°C and then increased at >30°C. Low quality surimi produced higher textural values (stress and strain) when fibrinogen and thrombin mixture (3–5%) had been added. Nonlinear stepwise regression model showed no significant interaction effects between surimi and fibrinogen-thrombin mixture. However, the response trace plot showed that failure stress value of surimi gel was increased by the concentration of fibrinogen-thrombin, but decreased by water content.     

CHARACTERIZATION OF THE PROTEASES INVOLVED IN HYDROLYZING PADDLEFISH (POLYODON SPATHULA) MYOSIN

An extract from paddlefish surimi possessed activities of B, L, and H‐like cathepsins. The optimal pH was around 5.0 for cathepsins B and L, and was between 6.0–6.5 for the H‐like cathepsin. The enzyme activities were not impaired by heating at 40Cfor 20 min. However, the protease extract lost about 20% of its cathepsin B, 50% B+L, and 90% H‐like cathepsin activities after heating at 50C for 20 min. The activity of H‐like cathepsin was not inhibited by E‐64, suggesting that it did not belong to ike known cysteme protease group. The protease extract was capable ofhydrolyzing myosin heavy chain, producing a major fragments) around 140 kDa. Degradation of myosin by the protease extract was substantially reduced by protease inhibitors including E‐64, a protease inhibitor mixture, and bovine plasma powder.     

Gel‐forming ability of surimi from grass carp (Ctenopharyngodon idellus): influence of heat treatment and soy protein isolate

The effects of setting conditions and soy protein isolate (SPI) on textural properties of surimi produced from grass carp were investigated. Effects of setting temperature, setting time and protein concentration on the breaking force and distance were evaluated and compared utilizing response surface methodology. Models for breaking force and breaking distance of grass carp surimi were established. Protein concentration was the major factor affecting the gel strength of grass carp surimi. Breaking force and distance of grass carp surimi gels decreased with increase of protein ratio from SPI at 30 °C and 40 °C for 60 min setting and heating at 85 °C for 30 min, but the breaking force obtained for addition of 100 g kg^?1 SPI protein to grass carp surimi was higher than that for surimi alone at 60 °C for 60 min incubation and heating at 85 °C for 30 min. Copyright © 2005 Society of Chemical Industry     

Effects of Hydrolysates from Silver Carp (Hypophthalmichthys molitrix) Scales on Rancidity Stability and Gel Properties of Fish Products

This study aimed to evaluate the effectiveness of hydrolysates, which were obtained from the scales of silver carp (Hypophthalmichthys molitrix) by papain, flavourzyme, and Alcalase 2.4 L, as natural antioxidants in silver carp mince and surimi gels during storage at 4 °C. The hydrolysates that possess greater in vitro antioxidant activities (DPPH radical-scavenging activity, Fe²⁺-chelating activity, and reducing power), including hydrolysates catalyzed by papain at 10 min (HP), flavourzyme at 5 min (HF), and Alcalase 2.4 L at 5 min (HA), were chosen as additives. Color, cooking loss, conjugated dienes (CDs), thiobarbituric acid reactive substances (TBARS), fatty acids, and sensory scores of mince were measured on days 0, 2, 4, 6, and 8 during 4 °C storage; additionally, whiteness, breaking force, deformation, gel strength, and sensory score of surimi gels were measured on days 1, 3, 5, 7, 9, and 11 during 4 °C storage. The results indicate that HA was conducive to lowering the cooking loss of mince and that HF significantly (P?<?0.05) reduced the CDs value of mince. For surimi gels, HF improved whiteness, deformation, and gel strength. Hence, HF could serve as a natural antioxidant during early oxidation and improve gel formation of silver carp products.     

Setting Response of Alaska Pollock Surimi Compared with Beef Myofibrils

Physicochemical properties of surimi after preincubation at 25–50°C and beef myofibrils at 25–60°C for up to 8 hr prior to cooking at 80°C for 20 min were evaluated by a torsion test and sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Shear stress and true shear strain of surimi were more sensitive to pH changes than beef myofibrils. Maximum gel strength was found at = pH 7 for surimi and pH 6 for beef myofibrils. The myofibrils showed no setting effect at any preincubation temperatures examined, while surimi showed an optimum setting effect at 25°C. Incorporation of beef myofibrils into surimi resulted in decrease of shear stress and true shear strain values.     

Heat-Induced Gelation Properties of Surimi From Mechanically Separated Chicken

Chicken surimi was prepared from fresh mechanically separated chicken meat using a sodium bicarbonate washing process. The heat-induced gelation properties were assessed under different conditions of pH, temperature, heating rate, protein and sodium tripolyphosphate (TPP) concentrations. Surimi gel strength increased (p < 0.05) after: reducing pH from 6.4 to 6.0, increasing temperature from 40°C to 80°C, reducing heating rate from 5°C/min to 1°C/min, increasing protein concentration from 4% (w/w) to 8% (w/w) or addition of 0.3% (w/w) TPP. Freeze thaw stability studies revealed that the gel strength of surimi decreased (p < 0.05) when subjected to frozen storage at – 18°C.