Protease Inhibitor Effects on Torsion Measurements and Autolysis of Pacific Whiting Surimi

Beef plasma protein (BPP), egg white and potato extract were tested for their ability to inhibit proteolysis in fish mince and surimi made from Pacific whiting (Merluccius productus). Strong inhibition resulted from all three compounds in fish mince when measured by autolysis. However, when tested in surimi significant differences occurred among the compounds. BPP showed strongest inhibition of proteolytic effect followed by egg white and potato extract when measured by autolysis, gel electrophoresis and torsion. BPP was an effective inhibitor in surimi at a concentration as low as 1%.     

Pig plasma protein: potential use as proteinase inhibitor for surimi manufacture; inhibitory activity and the active components

The inhibitory activities of pig plasma protein (PPP) against proteinases and autolysis were studied. Using casein as a substrate, it was shown that PPP exerted inhibitory activity against Pacific whiting (PW) proteinase, papain and trypsin. At levels of 10 and 20 mg ml⁻¹, PPP showed higher inhibitory activity than beef plasma protein (BPP) or egg white against PW proteinase (P < 0.05). The inhibitory activity was proportional to the concentration of PPP used up to 10 mg ml⁻¹. PPP and BPP showed marked inhibition of autolysis of PW surimi at concentrations of 10–30 mg g⁻¹. Egg white showed lower inhibition than PPP or BPP against autolysis of surimi (P < 0.05). Myosin heavy chain (MHC) in Pacific whiting surimi was better retained when higher concentrations of PPP were used, while no changes in actin were observed. Inhibitory activity staining on sodium dodecyl sulphate (SDS) substrate gels incubated with papain or trypsin indicated that residual protein bands with apparent molecular weights of 60 000–63 000 may be the active inhibitory components in PPP. These bands were found in PPP and bovine plasma fraction IV‐1, although only under non‐reducing conditions. © 2000 Society of Chemical Industry     

Bovine Plasma Protein Functions in Surimi Gelation Compared with Cysteine Protease Inhibitors

The protease inhibitory activity of bovine plasma protein (BPP) and its gel strengthening effect on Pacific whiting surimi were compared with E-64 [L-trans-epoxysuccinylleucylamido (4-guanidio) butane], iodoacetic acid (IAA), and a recombinant soybean cystatin (RSC). In terms of inhibitory activity, as low as 1.2 mM E-64,37.7 mM IAA, or 17.9 mg RSC were equivalent to 1% BPP. To produce the same gel strength as the 1% BPP-treated surimi, 10 times that level of E-64 and RSC were required, while 100 times that level of IAA did not increase the gel stress as effectively. Thus, plasma contributed to enhanced gelation of Pacific whiting surimi by inhibition of fish protease and also by other gel-enhancing factors in the plasma.     

Gelation of Surimi by High Hydrostatic Pressure

The effects of high hydrostatic pressure (HHP) on gel strength of Pacific whiting and Alaska pollock surimi were determined by torsion. Pacific whiting gels were made with and without 1% beef plasma protein (BPP) as protease inhibitor. HHP treated whiting (1% BPP added) and pollock gels showed greatly increased strain values at all pressure/temperature combinations compared with heat-set controls. Stress values for the same samples were variable depending on treatment and species. A three-fold increase in strain and stress was found for HHP treated whiting gels made without inhibitor.     

INHIBITION OF PACIFIC WHITING SURIMI-ASSOCIATED PROTEASE BY WHEY PROTEIN CONCENTRATE

Three whey protein concentrate (WPC) samples ranging in protein content from 34 to 95%, beef plasma protein (BPP) and bovine serum albumin (BSA) were analyzed for their effect on the autoproteolytic activity of Pacific whiting surimi. Autoproteolysis activity was determined in control and supplemented surimi containing up to 4% additive by measuring the amount of TCA-soluble peptides produced under defined reaction conditions. The degradation of specific myofibrillar proteins was followed electrophoretically. The extent of inhibition by the WPCs showed a general correlation with their respective protein contents. Autoproteolysis was essentially undetectable in surimi samples supplemented at the 2% level with either the 80% or 95% protein WPCs. Autoproteolysis was decreased by 57% relative to the nonsupplemented control in surimi containing 2% of 34% protein WPC. No proteolytic activity could be detected in surimi samples supplemented at the 1% level with BPP. Supplementation of surimi with up to 4% BSA had no demonstrable effect on autoproteolysis. The extent of proteolytic degradation of the myosin and tropomyosin fractions within surimi samples were in general agreement with the measured rates of autoproteolysis.     

Effect of Various Types of Egg White on Characteristics and Gelation of Fish Myofibrillar Proteins

ABSTRACT:  Three types of egg white protein (regular dried egg white [REW], special dried egg white [SEW], and liquid egg white [LEW]) were compared for their effect in surimi (CON), containing no egg white (EW). They were characterized for enzyme inhibition and time of EW addition, either with cryoprotectants prior to freezing or during gel preparation, using Pacific whiting surimi. In addition, the setting (suwari) effect and fish protein–EW protein interactions (dynamic rheological properties, total sulfhydryl groups, and fracture gel analysis) were evaluated using Alaska pollock surimi. After 12 mo frozen storage, adding 2% and 3% SEW to Pacific whiting surimi during chopping significantly ( P  < 0.05) increased the force and deformation values compared to adding the respective EW before freezing. The highest ( P  < 0.05) force (175.2 g) and deformation (9.0 mm) values after 12 mo were obtained when 3% SEW was added during chopping. Enzyme autolysis showed that addition of 2% EW protein was effective at inhibiting enzyme activity. During setting, adding 2% SEW maintained force (1047.4 g) and deformation (17.9 mm) values similar ( P  > 0.05) to CON (1055.1 g; 19.3 mm) and significantly ( P  < 0.05) better than 2% REW (666.1 g; 15.6 mm). Texture results corresponded well to other data where 2% SEW showed the lowest total sulfhydryl groups (48.3 mole/10⁵ g), and higher elastic modulus (G'), which suggests improved protein interaction for gel formation. Overall, the addition of 2% to 3% SEW improved gel textural properties of Pacific whiting and Alaska pollock fish protein.     

The effect of egg albumen on the viscoelasticity of crab sticks made from Alaska Pollock and Pacific Whiting surimi

The influence of the amount of egg albumen contained as a gelation agent in crab sticks made from Alaska Pollock or Pacific Whiting surimi on their viscoelastic properties was examined. Dynamic oscillatory and transient tests allowed a variety of parameters to be measured in order to establish the intensity of the interactions in the protein network which characterize the gel strength. This physical property is fundamental for the nominal quality texture and eating quality of surimi and surimi-based seafood analog products (surimi seafood). Three different egg albumen contents around the nominal value (2%) were studied, namely: 1.5, 2 and 2.5%. The viscoelastic gel strength (A_n) and gel strength (S) values obtained in the frequency sweep and creep tests, respectively, were quite consistent. Increasing the protein content of the surimi increased the gel strength of both types of crab sticks (p < 0.05). The optimum egg albumen content was found to be about 1.5% for Alaska Pollock and 2% for Pacific Whiting surimi. Based on these results, the industry could use less albumen in making crab sticks from Alaska Pollock surimi, which surpasses Pacific Whiting surimi in quality.     

Effect of protein additives, sodium ascorbate, and microbial transglutaminase on the texture and colour of red tilapia surimi gel

Beef plasma protein (BPP) and egg white, at levels of 10, 20 and 30 g kg⁻¹, and sodium ascorbate (SA) and microbial transglutaminase (MTGase), at levels of 1, 2 and 3 g kg⁻¹, were individually added into red tilapia surimi. This gel was set at 40 °C for 90 min followed by heating at 90 °C for 30 min. Gel qualities were analysed and compared with those of non-supplemented red tilapia control gel. Compared with the control, each additive significantly affected gel strength due to an increase in breaking force. Although BPP could improve texture characteristics, higher addition levels of BPP significantly affected gel whiteness. The addition of SA and MTGase were found to increase surimi gel strength and improve whiteness. Amongst all treatments, the addition of 2 g kg⁻¹ MTGase was found to provide the best gel qualities.     

Functional Properties and Shelf Life of Fresh Surimi from Pacific Whiting

Total aerobic plate count (APC), shear stress, shear strain, and color of fresh Pacific whiting surimi stored at 5°C were determined at day 0, 1, 3, 5, and 7. Frozen surimi was prepared with four levels of cryoprotectams (0, 3, 6, and 9%) and was compared with fresh surimi for gelforming ability. Fresh Pacific whiting surimi had a shelf life of 5 days. The gel functionality remained unchanged throughout the storage time. Strain values of fresh surimi were not different from those of frozen surimi with 9% cryoprotectants, but stress values of fresh surimi were almost three times higher than those of frozen surimi.     

花椒水提物对鳜鱼鱼糜凝胶特性的影响

为探索花椒水提物（Zanthoxylum bungeanum aqueous extract,ZBAE）对鳜鱼鱼糜凝胶特性的影响,研究ZBAE添加量为0、0.125%、0.25%、0.5%和1.0%时,该鱼糜凝胶持水性、凝胶强度、质构、白度、二级结构和微观结构的变化。结果表明,随着ZBAE添加量增加,持水性、凝胶强度、硬度和胶着性指标均呈现先增强再减弱的趋势,并且在0.25%时均达到最大值;傅里叶红外光谱检测表明,ZBAE的添加使α-螺旋、β-折叠和无规则卷曲的相对含量值呈现先上升后下降的趋势,其中,添加量为0.125%和0.25%时,分别对应β-折叠和α-螺旋的最高值;扫描电子显微镜结果显示,ZBAE添加量为0.25%时,该凝胶网络结构更致密,分形维数、孔隙率和孔数量均显著优于未添加组（P<0.05）;此外,低添加量（<0.25%）的花椒水提物能够提高鱼糜凝胶的感官品质。因此,ZBAE具有改善鱼蛋白凝胶特性的潜力。     

表没食子儿茶素没食子酸酯对冷冻罗非鱼鱼糜抗冻作用机制

通过肌原纤维蛋白理化指标、鱼糜凝胶特性的测定及十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE）,研究表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）对冷冻罗非鱼鱼糜的抗冻效果并探讨其作用机制。结果表明,罗非鱼鱼糜中添加EGCG具有一定的抗冻效果,对比空白组具有显著差异性。冻藏期间空白组鱼糜中盐溶性蛋白含量、总巯基含量分别下降了68.2%和62.9%,而添加0.01% EGCG后二者的降幅分别为54.5%和49.2%,且EGCG还明显延缓了肌原纤维蛋白的氧化羰基化作用。此外,冻藏过程中,EGCG组和空白组鱼糜凝胶强度和持水性随冻藏时间延长逐渐降低,且EGCG添加量较大时,反而加快凝胶劣化。SDS-PAGE显示,EGCG能够有效抑制肌原纤维蛋白降解,其中质量分数为0.01%的EGCG效果最佳。EGCG能延缓肌原纤维蛋白变性和降解程度,延缓鱼糜氧化变质程度,有望成为一种新型的鱼糜抗冻剂。     

Linear Heating Rate Affects Gelation of Alaska Pollock and Pacific Whiting Surimi

Shear stress of Alaska pollock surimi gels with and without beef plasma protein (BPP) increased as heating rate decreased, but shear strain was unaffected. An increase in shear stress was accompanied by an increase of cross-linked myosin heavy chain. Slow heating rates increased proteolysis in Pacific whiting surimi as shown by degradation of myosin heavy chain and low shear stress and shear strain. Proteolysis of whiting surimi was lessened by BPP to a greater extent at rapid heating rates (20 and 30°C/min) than at slow heating rates (1 and 5°C/min).     

USE OF CYSTEINE PROTEINASE INHIBITORS FROM INJURED TOMATO LEAVES IN WHITING SURIMI

Cooking surimi paste from Pacific whiting results in a gel with poor texture due mainly to myosin degradation caused by a cysteine proteinase. Cysteine and serine proteinase inhibitors were isolated from injured and methyl jasmonate treated tomato leaves. Tomato cysteine proteinase inhibitor was stable at 60C but inactivated at 90C, making it suitable for use in surimi. Tomato proteinase inhibitors (TPI), having 7.9 papain inhibitor units, inhibited autolysis about 95% in 10 g of Pacific whiting surimi. Gel strength of Pacific whiting surimi was improved by adding only 0.0 27% of TPI to the surimi formulation. Addition of TPI did not affect the color of whiting surimi gel, while egg white needed to prevent gel weakening caused the gels to have more yellow hue (P<0.05). SDS-PAGE showed that myofibrillar protein degradation was prevented during cooking when 0.027% of TPI was included in the surimi. TPI extracted from tomato plants has potential for use as food grade additive in Pacific whiting surimi.     

羧甲基壳聚糖与NaCl组合漂洗制备白鲢鱼糜工艺条件优化

目的：探讨羧甲基壳聚糖（carboxymethyl chitosan,CBC）与NaCl组合漂洗白鲢鱼糜对凝胶品质、鱼糜收率及蛋白损失率等的影响。方法：以鲜白鲢鱼为原料,分别采用去离子水、0.25%、0.5%、0.75%、1.0%的NaCl溶液,0.5%、1.0%、1.5%、2.0%的CBC溶液,1.0% CBC＋1.0% NaCl、1.0% CBC＋0.75% NaCl、1.5% CBC＋1.0% NaCl、1.5% CBC＋0.75% NaCl,对鱼糜进行一次漂洗（鱼肉与漂洗液质量比1∶5）,测定不同漂洗处理对鱼糜凝胶强度、白度、蛋白质组成及流变特性的影响。结果：单独采用NaCl漂洗时,随着其用量的增大,鱼糜凝胶强度、白度呈现增加趋势（P＜0.05）,总蛋白含量呈现先增加后下降的趋势,过高或过低的NaCl质量分数,均不利于提高鱼糜得率。单独采用CBC溶液漂洗时,凝胶强度、白度、水溶性蛋白含量随着CBC质量分数的增大呈上升趋势（P＜0.05）。采用NaCl和CBC组合漂洗时,1.5% CBC＋0.75% NaCl组合得到的鱼糜凝胶强度最高,达232.05 g•cm,显著高于对照的142.22 g•cm（P＜0.01）,此时的盐溶性蛋白含量10.53%和水溶蛋白含量4.91%,显著高于空白对照的9.36%（P＜0.05）及4.06%（P＜0.01）。1.5% CBC＋0.75% NaCl组合漂洗,获得良好的鱼糜凝胶强度、白度及粗蛋白含量。结论：采用1.5% CBC＋0.75% NaCl漂洗可以改善鱼糜的凝胶品质,蛋白损失率比对照组降低10.56%,从而提高鱼糜得率,并降低废水排放。     

内源性蛋白酶对鱼糜凝胶的影响及其抑制方法研究进展

研究豆粕蛋白添加量对白鲢鱼糜凝胶特性的影响,并进一步从化学作用力、蛋白二级结构等角度分析影响原因。向冷冻白鲢鱼糜中分别添加0%、0.5%、1.0%、1.5%和2.0%的豆粕蛋白制备鱼糜凝胶,采用质构仪、傅里叶变换红外光谱仪等测定鱼糜凝胶的持水性、蒸煮损失率、白度值、质构特性、感官品质以及化学作用力、总巯基含量和蛋白质二级结构等指标。结果表明：当豆粕蛋白的添加量占冷冻白鲢鱼糜的1.5%时,鱼糜凝胶的持水性、硬度、弹性、内聚性和咀嚼性分别为87.59%±1.44%、381.70±7.64 g、12.41±0.67 mm、0.89±0.02和38.60±0.14 mJ,且均升至最高,同时蒸煮损失率降至最低,为10.20%±0.52%,感官品质亦达最佳,白度值稍有降低。豆粕蛋白添加量为1.5%时,鱼糜凝胶的疏水相互作用和总巯基含量均达到最大,形成了紧密的凝胶三维网状结构。此外,豆粕蛋白的添加对鱼糜蛋白二级结构的影响较小。综合考虑,当豆粕蛋白添加量为1.5%时,有效地改善了鱼糜制品的凝胶特性。     

小麦蛋白和谷氨酰胺转氨酶对120℃高温处理鱼糜凝胶特性影响的研究

以阿拉斯加狭鳕鱼糜为原料,研究了小麦蛋白和谷氨酰胺转氨酶(TG酶)对120℃高温杀菌鱼糜制品凝胶特性的影响。通过分别测定在一段加热和两段加热两种加热方式下,添加小麦蛋白和TG酶的复合样品的破断力,破断距离,凝胶强度,动态流变学,白度和扫描电镜等指标,发现二者的添加对高温处理鱼糜凝胶的破断力,破断距离均有较好的改善效果,可显著增强其凝胶强度(p<0.01)。尤其是同时添加两种添加剂对鱼糜凝胶特性的增强更为显著,采用两段加热成型的方式其凝胶强度可增加至2倍。扫描电镜观察结果表明同时添加两种添加剂的杀菌鱼糜具有更为致密的凝胶网络结构。添加TG酶的样品采用二段加热比直接杀菌成型有更好的凝胶特性,而添加小麦蛋白会使鱼糜凝胶发黄导致白度降低。本文为以后高温杀菌鱼糜制品的研发提供了依据。      

L-赖氨酸对低盐鱼糜凝胶特性的影响

为提高低盐鱼糜制品的品质,研究了L-赖氨酸(L-Lys)添加量对低盐鱼糜凝胶的质构、色泽、持水性、水分流动性和流变特性的影响。结果表明鱼糜凝胶强度随着L-Lys添加量的增加呈现先增加后降低的趋势,添加0.1% L-Lys能够使低盐鱼糜凝胶(1.0% NaCl)达到与对照鱼糜凝胶(2.5% NaCl)相当的凝胶强度;随着L-Lys添加量的增大,鱼糜凝胶的pH和持水性增大,而L-Lys添加量对鱼糜凝胶色泽的影响不显著;添加L-Lys使鱼糜凝胶不易流动水的比例提高,易流动水比例降低。动态流变结果表明,G'达到第一个峰值的温度随着L-Lys 添加量的增加而下降,且显著低于对照组(p<0.05);G'达到最低点的温度随着L-Lys 添加量的增加而增大,且显著高于对照组(p<0.05)。添加0.1% L-赖氨酸能够提高鱼糜制品的凝胶特性,为生产低盐鱼糜凝胶制品提供理论依据。     

添加微细鲽鱼鱼骨泥对金线鱼鱼糜凝胶品质的影响

以鲽鱼骨为研究对象,首先采用湿法超微粉碎技术将其加工成微细骨泥,再将其添加到金线鱼鱼糜制品中开发高钙鱼糜制品,从鱼糜溶胶pH值、肌原纤维蛋白Ca2＋-ATP酶活力、凝胶强度、质构、持水性、色泽、凝胶溶解度、微观结构方面探讨添加不同质量分数（2.5%～12.5%）鱼骨泥对鱼糜制品凝胶品质的影响。结果显示：添加微细鱼骨泥不影响鱼糜正常凝胶的pH值;较低质量分数（不超过5.0%）时,鱼骨泥中的Ca2＋可以激活鱼糜溶胶中肌原纤维蛋白的ATP酶,显著提升Ca2＋-ATP酶活力;鱼糜凝胶的凝胶强度、质构、持水性、色泽指标均在添加质量分数5.0%鱼骨泥时达到最高值,而凝胶溶解度达到最低值。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析和扫描电子显微镜观察结果表明,添加质量分数2.5%～5.0%鱼骨泥一定程度上促进了肌球蛋白重链（myosin heavy chain,MHC）的交联,可以促进鱼糜凝胶形成致密均匀的网状结构,过量添加则会影响MHC交联和凝胶网络致密性。     

Enhancing gel behavior of yellow croaker surimi by fruit extracts: Physicochemical properties and molecular mechanism

The aim of this study was to investigate the effects of grape seed extract (GSE), acerola cherry extract (ACE), and blueberry extract (BBE) on the physicochemical properties and structure of the yellow croaker surimi gel. In addition, molecular docking and molecular dynamics (MD) simulation were utilized to study the binding mechanism of yellow croaker's fibrillin and fruit extracts. Surimi gel with 1.5% GSE, ACE, and BBE had the highest water holding capacity, hardness, chewability, cohesion, breaking force, breaking distance, gel strength, and densest 3D network structure, according to the experiment's findings. Nevertheless, the cross-linking of proteins in surimi was blocked with the further increase of fruit extract (1.5%–2.0%), and the existing network of surimi was weakened or even destroyed. Three fruit extracts had little effect on the secondary structure of the surimi gel. Besides, hydrophobic and disulfide bonds are the main chemical bonds of croaker surimi. Molecular docking showed that B-type procyanidine (BP) interacted with ASN-183, SER-571, ASP-525, ARG-350, LYS-188, GLU-349, CYS-353, and other active amino acids in croaker protein. Moreover, it can form strong hydrogen bond interaction with ASN-183, SER-571, ASP-525, and ARG-350 at the active sites of protein. The BP-Larimichthys crocea protein system's MD simulation was carried out, and calculations for the simulation's root mean square deviation, root mean square fluctuation, radius of gyration, solvent accessible surface area, and hydrogen bonds were made. It was found that these indices can demonstrate that the BP binding contributes to the stability of the yellow croaker structure.     

Nano eggshell calcium enhanced gel properties of Nemipterus virgatus surimi sausage: gel strength,water retention and microstructure

The effects of nano eggshell calcium (NEC) at different levels (0–1.5 g/100 g) on the gel properties of Nemipterus virgatus surimi were investigated. The results indicated that under the condition of adding 1.0 g/100 g, the gel strength of surimi was the highest, the water-holding capacity (WHC) was the best, and the cooking loss was the lowest. Sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the addition of NEC promoted the covalent cross-linking between myosin heavy chains (MHC). Raman spectroscopy demonstrated that low contents (0.5–1.0 g/100 g) of NEC promoted the conformational transition of surimi protein from α-helix to β-sheet. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) showed that the surimi gel with 1.0 g/100 g NEC had a denser network structure. Nevertheless, in the mixed gel with 1.25–1.5 g/100 g NEC, the network structure of the mixed-protein matrix was disrupted, and the mechanical and physicochemical parameters were deteriorated.