Modori Gel Research Articles

Effect of pH-Shifting Process on the Cathepsin Activity, Muddy Off-Odor Compounds' Content and Gelling Properties of Isolated Protein from Silver Carp.

Silver carp (Hypophthalmichthys molitrix) is a potential source for making surimi products. However, it has the disadvantages of bony structures, high level of cathepsines and muddy off-odor which is mainly caused by geosmin (GEO) and 2-methylisoborneol (MIB). These disadvantages make the conventional water washing process of surimi inefficient (low protein recovery rate, and high residual muddy off-odor). Thus, the effect of the pH-shifting process (acid-isolating process and alkali-isolating process) on the cathepsins activity, GEO content, MIB content, and gelling properties of the isolated proteins (IPs) was investigated, comparing it with surimi obtained through the conventional cold water washing process (WM). The alkali-isolating process greatly boosted the protein recovery rate from 28.8% to 40.9% (p < 0.05). In addition, it removed 84% GEO and 90% MIB. The acid-isolating process removed about 77% GEO and 83% MIB. The acid-isolated protein (AC) displayed the lowest elastic modulus (G'), the highest TCA-peptide content (90.89 ± 4.65 mg/g) and the highest cathepsin L activity (65.43 ± 4.91 U/g). The AC modori (60 °C for 30 min) gel also demonstrated the lowest breaking force (226.2 ± 19.5 g) and breaking deformation (8.3 ± 0.4 mm), indicating that proteolysis caused by the cathepsin deteriorated the gel quality of AC. The setting (40 °C for 30 min) considerably increased the breaking force (386.4 ± 15.7 g) and breaking deformation (11.6 ± 0.2 mm) of the gel made from the alkali-isolated protein (AK) (p < 0.05). In AC and AK gel, a clearly visible cross-linking protein band with a molecular weight greater than MHC was seen, demonstrating the presence of endogenous trans-glutaminase (TGase) activity, that improved the gel quality of AK. In conclusion, the alkali-isolating process was an effective alternative method for making water-washed surimi from silver carp.

Role of Endogenous Cathepsin L in Muscle Protein Degradation in Olive Flounder (Paralichthys olivaceus) Surimi Gel.

We investigated the effect of endogenous cathepsin L on surimi gel produced from olive flounder (Paralichthys olivaceus). The amino acid sequences of six proteins predicted or identified as cathepsin L were obtained from the olive flounder genome database, and a phylogenetic analysis was conducted. Next, cathepsin L activity toward N-α-benzyloxycarbonyl-l-phenylalanyl-l-arginine-(7-amino-4-methylcoumarin) (Z-F-R-AMC) was detected in crude olive flounder extract and a crude enzyme preparation. A considerable decrease in the level of myosin heavy chain (MHC) in surimi occurred during autolysis at 60 °C. In contrast, the levels of actin, troponin-T, and tropomyosin decreased only slightly. To prevent protein degradation by cathepsin L, a protease inhibitor was added to surimi. In the presence of 1.0% protease inhibitor, the autolysis of olive flounder surimi at 60 °C was inhibited by 12.2%; the degree of inhibition increased to 44.2% as the inhibitor concentration increased to 3.0%. In addition, the deformation and hardness of modori gel increased as the inhibitor concentration increased to 2.0%. Therefore, cathepsin L plays an important role in protein degradation in surimi, and the quality of surimi gel could be enhanced by inhibiting its activity.

Gel-Forming Ability of Rohu as Affected by Egg White Powder Addition

The gel-forming ability of rohu (Labeo rohita) mince with and without egg white powder (EW) was investigated. Gel from washed mince (washed gel) was prepared under two setting conditions: kamaboko (40°C) and modori (60°C). The gel-forming ability of kamaboko and modori gels was improved by the addition of EW at 2%. The autolytic inhibition of kamaboko gel was obtained in gel added with 2% EW, and 1% EW of modori gel. No marked change was observed in the TCA-soluble peptide content of either gel with the addition of EW above 1%. No effect on the whiteness of both gels was shown after the addition of EW. The addition of EW exhibited smaller cavities and a more compact fibrous network in microstructure.

Serine protease inhibitors from squid ovary: extraction and its effect on proteolysis and gel properties of surimi.

Serine protease inhibitors from squid ovary (SOSPI) were extracted using different extraction media and conditions. Optimal condition included 0.45M NaCl for 1h. After heat treatment at 70°C for 10min, the highest specific activity was obtained. Based on Sephadex G-75 gel filtration and activity staining, the major SOSPIs were present as monomer with molecular weight of 9.10 and 10.27kDa. Impact of SOSPI on autolysis of bigeye snapper surimi was studied. Myosin heavy chain was more retained with coincidentally lower trichloroacetic acid-soluble peptide content as the level of SOSPI increased. When SOSPI at various levels (0.5-3%) was added into surimi, the highest breaking force of both kamaboko and modori gels containing 1% SOSPI was obtained. However, SOSPI had no effect on deformation of kamaboko gel but slightly increased the deformation of modori gel. SOSPI increased water holding capacity of both kamaboko and modori gels in a dose dependent manner, as indicated by the lowered expressible moisture content. SOSPI had no effect on the whiteness of both gels. Thus SOSPI can be used as the protein additive in surimi for increasing breaking force.

Effect of bambara groundnut protein isolate on autolysis and gel properties of surimi from threadfin bream (Nemipterus bleekeri)

Impact of bambara groundnut protein isolate (BGPI) on autolysis and gel properties of surimi from threadfin bream (Nemipterus bleekeri) was investigated. BGPI with trypsin inhibitory activity of 6356.3 ± 6.02 unit/g markedly increased (P < 0.05) the breaking force and deformation of modori gel as the levels used (0–3 g/100 g) increased. Nevertheless, only 0.25 g/100 g BGPI increased breaking force and deformation of kamaboko gel and increasing BGPI levels showed detrimental effect on gelation. Myosin heavy chain (MHC) was more retained when BGPI concentration increased, especially in modori gel. However, whiteness slightly decreased (P < 0.05) with increasing BGPI levels. Microstructure of kamaboko gel added with 0.25 g/100 g BGPI had finer and more ordered fibrillar structure than that without BGPI addition. Therefore, BGPI at an appropriate level could be an alternative food-grade inhibitor to improve gel properties of surimi.

Gelling characteristics of surimi from yellow stripe trevally (Selaroides leptolepis)

Yellow stripe trevally (Selaroides leptolepis) is one of the abundant dark-fleshed fish species caught in Southern Thailand. However, the pelagic fish have high content of dark flesh associated with the high lipid and myoglobin contents contributing to the difficulties in making high-quality surimi. However, setting or heating at an appropriate temperature can improve the property of gel by avoiding the degradation but enhancing cross-linking of proteins. Therefore, the objective of this study was to investigate the gel-forming ability of surimi from yellow stripe trevally prepared under different heating conditions. Surimi gels were prepared under different heating conditions. Textural properties, whiteness, expressible moisture content, trichloroacetic acid (TCA)-soluble peptide content, protein pattern and microstructure of gels were determined. Additionally, the optimal temperature of muscle transglutaminase (TGase) was determined using monodansyl cadaverine incorporation method. Kamaboko gel with prior setting at 40°C (K40) exhibited the highest breaking force, followed by another kamaboko gel having setting temperature of 25°C, directly heated gel and modori gel, respectively (p < 0.05). For deformation, both kamaboko gels showed the lower values than both directly heated gel and modori gel (p < 0.05). The lowest expressible moisture content and whiteness were found in K40 sample (p < 0.05). The optimal temperature of yellow stripe trevally muscle transglutaminase was found to be 40°C. The highest TCA-soluble peptide content with decreased myosin heavy chain was found in modori surimi gel (p < 0.05). K40 sample had finer and more ordered fibrillar structure with smaller voids than other gels. Yellow stripe trevally could be used as the new raw material for surimi which yielded the gel with high deformation. Setting at 40°C is a promising means to improve the properties of surimi gel. Conversely, the incubation of sol at temperature close to 60°C should be avoided to prevent gel weakening.

COMBINATION EFFECTS OF WHEY PROTEIN CONCENTRATE AND CALCIUM CHLORIDE ON THE PROPERTIES OF GOATFISH SURIMI GEL

ABSTRACT Effect of whey protein concentrate (WPC) in combination with calcium chloride (50 mmol/kg) on the gel properties of surimi produced from goatfish (Mulloidichthys martinicus) was investigated. Breaking force and deformation of both kamaboko (40/90C) and modori (60/90C) gel increased with increasing WPC (0–3%) (P &lt; 0.05). Myosin heavy chain (MHC) band intensity of all gels was more retained as WPC concentration increased. The coincidental increase in water‐holding capacity was obtained, however, the whiteness was slightly decreased. At all levels of WPC added, kamaboko gels added with CaCl2 exhibited the superior properties to those without CaCl2 (P &lt; 0.05). On the other hand, CaCl2 addition resulted in the poorer gel properties of modori gel, regardless of WPC addition. The microstructure of surimi gels added with 3% WPC generally became denser and more ordered, compared with the control gel, irrespective of CaCl2 addition.PRACTICAL APPLICATIONSGoatfish is the new raw material for surimi production; however, it yields the gel with poor quality. The addition of WPC and CaCl2 at the appropriate levels can be a promising means to improve the gel quality via the inhibition of endogenous proteinases and the enhancement of setting phenomenon, respectively. As a consequence, surimi industry is able to produce surimi from goatfish with the quality equivalent to that of surimi from commonly used species. Thus, the greater benefit can be gained from goatfish, especially for the surimi industry.

Effect of Rainbow Trout (Oncorhynchus mykiss) Plasma Protein on the Gelation of Alaska Pollock (Theragra chalcogramma) Surimi

The effect of rainbow trout plasma protein (RPP) on the gelation of Alaska pollock surimi was determined to evaluate the possibility of its commercialization as a new protein additive. For modori gel, the breaking force, deformation, whiteness, and water holding capacity increased as the addition amount of RPP (0 to 0.75 mg/g) increased, and decreased at higher concentration of RPP (0.75 to 1.50 mg/g) (P < 0.05). Protein solubility of modori gel in the mixture of SDS, urea, and beta-mercaptoethanol decreased as the addition amount of RPP increased up to 0.75 mg/g, and increased at higher concentration of RPP (0.75 to 1.50 mg/g) (P < 0.05). The contents of trichloroacetic acid-soluble peptide decreased as the addition amount of RPP (0 to 1.50 mg/g) increased (P < 0.05). Based on the result of sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE), most myosin heavy chain of surimi was not degraded when RPP was added. Thus, RPP was supposed to act as a protease inhibitor in the gelation of Alaska pollock surimi. An RPP of 0.75 mg/g was the optimal concentration to prevent the gel weakening of Alaska pollock surimi. Compounds with molecular weights less than 10 kDa in RPP had no significant effect on the gelation of Alaska pollock surimi based on the result of the dialyzed RPP.

Application of Recombinant Chum Salmon Cystatin to Alaska Pollock (Theragra chalcogramma) Surimi to Prevent Gel Weakening

Recombinant chum salmon cystatin (RC) expressed in Saccharomyces cerevisiae was purified by His-select nickel affinity chromatography. The specific inhibitory activities of RC against papain and cathepsin L were 7.45 and 10.24 U/mg, respectively. RC was stable over pH 5.0 to 7.0 and at temperature below 65 degrees C. RC was used to prevent the gel weakening of Alaska pollock surimi. RC at 100 microg/g showed the highest inhibitory activity against the autolysis of surimi based on the analysis of TCA-soluble peptides. As the concentration of RC increased, both the breaking force and deformation of modori gel greatly increased (P < 0.05). The addition of RC resulted in less expressible drip, which coincided with the increase of whiteness. More myosin heavy chain (MHC) was retained as the addition of RC increased. Therefore, RC could prevent the degradation of proteins in Alaska pollock surimi and was better than egg white (EW). Thus, RC could be applied to Alaska pollock surimi to prevent gel weakening and RC at 100 microg/g was the optimal concentration.

Effect of cysteine proteinase inhibitor containing fraction from chicken plasma on autolysis and gelation of Pacific whiting surimi

The effects of cysteine proteinase inhibitor containing fraction (CPI fraction) from chicken plasma on autolysis inhibition and gelling properties of Pacific whiting surimi were investigated. The CPI fraction exhibited the inhibitory activity against autolysis of Pacific whiting surimi in a concentration-dependent manner. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern revealed that the CPI fraction effectively prevented the degradation of myosin heavy chain, tropomyosin and troponin-T in Pacific whiting surimi incubated at 55 °C for 60 min as well as modori gel (55 °C for 30 min/90 °C for 20 min). The breaking force and deformation of modori gels increased as the concentration of CPI fraction increased up to 2.0% with a concomitant decrease in TCA-soluble peptides ( p<0.05). However, a decrease in breaking force and deformation was noticeable with the modori gel added with 3% CPI fraction. The addition of CPI fraction had no detrimental effect on whiteness of surimi gels ( p>0.05). The result suggested that CPI fraction would be an alternative additive for surimi containing the active cysteine proteinase causing the gel weakening.

Effect of Setting Temperatures and Time on the Gelation Properties (Suwari and Modori Phenomena) of Surimi from Mechanically Deboned Chicken Meat

This study was carried out to investigate gel forming and degradation properties (suwari and modori phenomena) of chicken surimi from mechanically deboned chicken meat (MDCM) at various setting temperatures and time. Chicken surimi was manufactured by a continuous process including chopping of MDCM, washing with 5% NaCl solution or pure water, standing, straining and centrifuging etc. Total process of washing for the MDCM from chopping to centrifuging was repeated over 3 cycles. Gel from prepared surimi were formed at 90°C for 30 min after various setting treatments. The textural properties of gels were measured at the temperature ranges of low (10°C), medium (25°C and 30°C) and high (45 to 70°C). The compressive force (CF), hardness and fracturability of surimi gel at 10°C increased as setting time increased, and showed the highest value at 30 h of setting time. The CF and hardness of chicken surimi gel at 25°C and 30°C showed the highest values at 10 h of setting time. Most of gel strengths including CF, and texture profile analysis (TPA) values showed the highest levels in the range 47.5 to 52.5°C (p<0.05). The gel strength at 60°C increased slightly at 30 min, but then continued to decrease with longer setting times. There was no increase of gel strength at 70°C, but only a continuous decrease over setting time. In conclusion, suwari (gel setting) and modori (gel degradation) phenomena occur during the gel formation of surimi from MDCM. The temperature range in chicken surimi was 47.5 to 52.5°C for suwari and 60 to 70°C for modori. (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 12 : 1758-1763)

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

: 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.