Inhibiting effect of polymerization and degradation of myosin heavy chain during preheating at 30°C and 50°C on the gel-forming ability of walleye pollack surimi

ABSTRACT: To confirm the contribution of polymerization and degradation of myosin heavy chain (MHC) during preheating to the gel-forming ability of fish meat paste, walleye pollack surimi paste was preheated at 30°C and 50°C prior to heating at 80°C in the presence of various inhibitors. At 30°C, ethyleneglycol bis(2-aminoethyl ether) -N,N,N ', N '-tetraacetic acid (EGTA) and ethylenediaminetetraacitic acid (EDTA) inhibited gel formation as well as the polymerization of MHC, whereas dithiothreitol (DTT) and leupeptin promoted gel formation, which was accompanied by the enhancement of MHC polymerization and decreased MHC degradation, respectively. At 50°C, leupeptin inhibited MHC degradation and improved gel strength, whereas EGTA, EDTA and DTT had no effect on MHC polymerization and degradation and did not affect gel formation. The results demonstrate that the gel strength of cooked gel (80°C) is not affected by preheating at 30°C and 50°C and does not inhibit polymerization and degradation. Results suggest that the gel strength of cooked gel is dependent on the polymerization and degradation of MHC during preheating.     

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.     

TG酶制剂对鱼糜凝胶强度的影响

本文研究了TG-K、TG-B、TG-AK三种酶制剂在不同的添加量、凝胶化时间下对冷冻蛇鲻鱼糜凝胶强度的影响。结果表明:三种酶制剂都有增强冷冻蛇鲻鱼糜凝胶强度的作用,以 0.15％的 TG-AK酶制剂,30℃时凝胶化 30分钟凝胶强度增强效果最好,此方案应用于鱼丸的生产,产品的凝胶强度弹性明显增强。     

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.     

鲢、狭鳕鱼糜微波加热凝胶形成的动力学分析

以鲢（Hypophthalmichthys mollitrix）和狭鳕（Theragra chalcogramma）鱼糜为对象,在微波、水浴两种加热条件下,对鱼糜及鱼糜大豆蛋白复合素材试样的凝胶特性——破断力值加以测定,进而考察不同加热方式下两种鱼糜的凝胶形成速度以及微波加热所需的活化能,并对试样能量吸收值进行了比较。结果表明：（1）鲢、狭鳕鱼糜微波加热凝胶形成速度比传统水浴加热高两个数量级,不同鱼种的鱼麋微波加热凝胶形成速度有一定的差异性（P〉0．05）。（2）微波加热下,欲达到相同的破断力值,鲢需要高于狭鳕1倍的活化能,两者对应的复合素材的活化能均小于相应的单一鱼糜试样。（3）与水浴加热相比,在能量吸收值相同的情况下,微波加热试样能达到更高凝胶破断力值。     

Effect of pH-shifting on the gel forming characteristics of salt-ground meat from walleye pollack

ABSTRACT:   In order to elucidate the mechanism of the changes in gel forming characteristics of fish meat by pH-lowering, the gelation-temperature curve and the gelation-moisture content curve were examined using the acidified walleye pollack surimi or neutralized one after acidification. In the gelation-temperature curve, the gel strength was highest at 30°C and lowest at approximately 50–60°C, irrespective of pH shifting. The gel strength at 30°C and 80°C decreased with the decrease in pH value. The neutralization of acidified surimi improved the gel strength, but it was considerably lower than the original gel strength. The gel strength at 50–60°C was not affected by pH lowering. The gel strength at 80°C could not be revived to the original by pH readjustment, either in the presence or in the absence of EDTA. These results suggest that irreversible changes of meat protein take place under the low pH, and the oxidation ability of sulfhydryl (SH) groups of protein molecule is not affected by pH-shifting.     

Thermal gelation properties of white croaker, walleye pollack and deepsea bonefish surimi after suwari treatment at various temperatures

The effects of setting (suwari) at around 40 °C on the breaking strength and breaking strain rate of thermal gels treated at 85 °C for 20 min during the following processing step were examined in association with the polymerization and degradation of myosin heavy chains (MHCs) for surimi prepared from white croaker, walleye pollack and deepsea bonefish. In the case of white croaker and walleye pollack, maximum values of breaking strength and breaking strain rate were obtained after suwari at 30–40 °C for both 30 and 60 min, at which temperature MHCs were polymerized. In comparison, these textual properties of the thermal gels decreased in surimi prepared from deepsea bonefish after suwari at around 38 °C for 30 min and at around 32 °C for 60 min, with concomitant degradation products of MHC. The textual properties of deepsea bonefish after suwari at temperatures >45 °C tended to be almost the same as those after suwari at temperatures of <30 °C, where neither polymerization nor degradation of MHC was observed.     

谷氨酰胺转胺酶对鱼糜品质的影响

为了综合利用小杂鱼资源,以冻杂鱼浆为原料,探讨了谷氨酰胺转氨酶(简称TGase)的添加量、作用时间、作用温度对鱼糜制品的弹性和凝聚性的影响。单因素试验和L9(34)正交试验结果表明,TGase的最佳工艺参数水平组合为TGae的用量为0.10%,TGase的作用温度为35℃,作用时间为1.5 h。     

Quality evaluation of frozen surimi by using pH stat for ATPase assay

To evaluate the quality of frozen surimi, the ATPase assay system was applied to pH stat. Surimi homogenate was prepared without washing procedures as a material for the measurement. Among the possible compounds frozen surimi contains, Mg ion slightly inhibited Ca-ATPase activity, while sugars or polyphosphate did not. Thus, the surimi homogenate was directly used for ATPase assay. The quality of surimi samples with various commercial grades were analyzed by measuring Ca-ATPase activity and protein content to obtain ATPase total activity. SA grade surimi showed high total activity, and was clearly distinguished from the second grade ones by the total Ca-ATPase activity. The specific Ca-ATPase activity contributed to the total activity more than the protein content. These results demonstrated that employment of surimi homogenate and the pH stat method made the total activity measurement of surimi easy and rapid.     

冷冻狭鳕鱼糜射频解冻温度数值模拟及验证

为快速分析鱼糜射频解冻过程中的温度分布情况,以狭鳕鱼糜介电特性和热物性参数为基础,通过COMSOL Multiphysics软件对射频解冻过程进行数值模拟,以有限元方法数值求解电磁波耗散及热传递耦合方程,并对数学模型进行试验验证。结果表明:狭鳕鱼糜的上表面、中间层和下表面的温度分布高度一致,数值求解结果与试验验证结果吻合,鱼糜各层的冷点位置始终位于鱼糜中心部位,热点位置始终位于鱼糜边角区域,鱼糜中间层的温度要明显低于上、下表面,鱼糜上表面温度要高于下表面。从升温速率上看,位于鱼糜中心部位的监测点升温速度最慢,位于鱼糜边角区域的监测点升温速率最快。鱼糜样品中9个监测点的温度实测值大部分落在模拟计算的温度变化曲线上。通过试验值与测定值的比较,表明应用COMSOL Multiphysics软件可较好地模拟射频加热过程的温度变化,从而用于预测物料的温度分布。     

淡水鱼鱼糜制品加工特性及品质影响因素

以罗非鱼 (Oreochromis niloticus×O. areus) 鱼糜为原料,通过向鱼糜中添加不同剂量的羧甲基琼胶 (Carboxymethyl agar, CMA),并测定鱼糜凝胶的强度、持水性、质构特性、色泽、蛋白化学组成和微观结构等指标,研究了CMA对鱼糜凝胶性能的影响。结果表明,添加量为0.5%~2.0%时,CMA可显著提高鱼糜的凝胶强度 (P<0.05),最高达70.7%;1.5%~2.5%的CMA可显著提高凝胶持水性 (P<0.05);添加量为1.5%~2.0%时,CMA对鱼糜凝胶的质构特性具有良好的改善效果;添加量为0.5%时,CMA对鱼糜凝胶具有显著的增白效果 (P<0.05);CMA对鱼糜蛋白化学作用力具有显著影响 (P<0.05),适量添加可以破坏离子键,促进氢键、疏水键和二硫键的形成,促使鱼糜发生胶凝化;SDS-PAGE电泳和扫描电镜分析结果显示,CMA促使了肌球蛋白重链 (Myosin heavy chain, MHC) 之间的交联,添加1.5%的CMA可使鱼糜凝胶形成均匀、致密的网络结构。总之,罗非鱼鱼糜中添加1.0%~1.5%的CMA,改变了鱼糜的持水性、化学作用力和蛋白质的聚集性,增强了蛋白质的交联作用,改进了鱼糜凝胶的网络结构,从而提升了鱼糜的凝胶性能。     

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.     

鱼排酶解物对鳙鱼鱼糜冻藏过程中蛋白质变性的影响

利用木瓜蛋白酶、低温碱性酶、风味蛋白酶酶解红鱼（Sciaerlops ocellatus）鱼排，分别获得木瓜蛋白酶酶解物（PPH）、低温碱性酶酶解物（LPH）和风味蛋白酶酶解物（FPH）。对3种酶解物化学成分及氨基酸组成进行分析，结果显示，3种酶解物中总氨基酸含量都在70％以上，总氮含量为82．12％～84．61％。酶解物分别以5％（质量比）量加入鳙鱼（Aristichthys nobilis）鱼糜中，冻藏于-20℃。测定冻藏过程中肌原纤维蛋白质盐溶性和Ca^2＋-ATPase活性的变化，同时测量鱼糜凝胶弹性的变化，并对冻藏样品进行扫描电镜观察，抗冻效果同商业抗冻剂（4％蔗糖、4％山梨醇、0．3％多聚磷酸盐混合剂）进行比较。结果表明，各酶解物能够在一定程度上抑制鱼糜蛋白质的冷冻变性，延缓肌原纤维蛋白质盐溶性和Ca^2＋-ATPase活性的下降，鱼糜凝胶质量下降减少，其中木瓜蛋白酶酶解物具有最好的效果。     

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.     

Identification of the glutamine residue that may be involved in the transglutaminase-mediated intramolecular crosslinking of carp and walleye pollack myosin

In order to elucidate the molecular mechanism of transglutaminase-mediated myosin crosslinking, a fluorescent monodansylcadaverine (MDC) was incorporated into carp Cyprinus carpio myosin and the reactive Gln residues were analyzed by cyanogen bromide cleavage. The fluorescence was predominantly detected in a 10.5 kDa BrCN fragment, assumed to be located in subfragment 2 of the myosin heavy chain. Furthermore, lysyl endopeptidase digestion of the 10.5 kDa fragment revealed that MDC was specifically incorporated into the 520th Gln residue of the subfragment 2 domain. When meat paste prepared from frozen walleye pollack (Theragra chalcogramma) surimi was incubated with MDC, the fluorescence was mostly observed in a 16 kDa BrCN fragment and also slightly detected in other three bands. By digesting the 16 kDa fragment with lysyl endopeptidase, it was elucidated that MDC was incorporated specifically into Gln-520 of myosin subfragment 2, as also detected in carp. This domain around Gln-520 is likely to be a critical region for the formation of myosin heavy chain dimers that both fish species have in common. In walleye pollack, other reactive Gln residues are presumed to exist at the C-terminus of the light meromyosin. This slight difference may have a significant effect on the capacity of myosin to form tetramers or even larger multimers.