Protein and water structural changes in fish surimi during gelation as revealed by isotopic H/D exchange and Raman spectroscopy

Structural changes of proteins and water during gelation of fish surimi, have been studied by isotopic H/D exchange of water and Raman spectroscopy assisted by monitoring of rheological characteristics, in order to get insights into the structural and functional properties of surimi gels. The results indicate the following: (i) Protein hydrogen bond rearrangements occur involving mainly α-helix to β-sheet transition, (ii) the relative intensity of the symmetric H₂O stretching band near 3220 cm⁻¹ tends to decrease upon gelation, (iii) H/D exchange reveal a slower deuteration kinetics in the gels as compared to the surimi, (iv) the low temperature scanning electron microscopy shows a smaller pore size of the gel network as compared to the surimi, and suggests that water domains in gel are more inaccessible to D₂O, which is consistent with higher water holding capacity in the gel.     

Porcine Plasma Proteins as a Surimi Protease Inhibitor: Effects on Actomyosin Gelation

Effect of porcine plasma proteins (PPP) on thermal gelation of actomyosin in the presence and absence of fish proteinase was studied using a dynamic rheological test. Substantial decreases in development rate and magnitude of gel modulus were observed by the addition of proteinase to actomyosin gels. PPP was effective in protecting a myosin-heavy chain from proteolytic degradation, however, PPP itself interfered with the formation of actomyosin gel. Lower gel modulus was observed with actomyosin gels developed with higher concentrations of PPP added. Overall, PPP reversed the loss of gel modulus by the proteinase, however, the recovered gel modulus was only as high as those containing PPP only. These results implicated that, although PPP may revert autolytic activity in surimi, it interfaces with actomyosin gelation.     

Kappa carrageenan fluid gel material properties. Part 1: Rheology

With the potential use of kappa carrageenan (κC) fluid gels in reduced fat foods, an understanding of their rheological properties was explored. Isotropic fluid gel particles were produced via sheared gelation of κC with potassium chloride. Bulk fluid gel rheological properties were tested for their dependence on particle elasticity and volume fraction (controlled through biopolymer concentration and dilution, respectively). To achieve this, a method for determining fluid gel particle volume fractions (Φ_FG) was devised using a novel centrifugation technique whereby the dependence of particle compressibility on centrifugation force is accounted for. The κC fluid gels prepared here are suggested to behave as soft microgel particles with penetrable hairy chains allowing for particle overlap, and aggregation at low volume fractions. The ‘hairy’ structures are proposed to arise from incomplete helix formation during gelation (which we previously confirmed using calorimetry) as a result of the applied shear disrupting the molecular ordering process which, for κC, is slow relative to that of biopolymers that do not form ‘hairy’ fluid gel structures.     

鳕鱼皮的添加对鱼糜凝胶特性及其蛋白质结构的影响

目的 研究添加黑线鳕鱼(Melanogrammusaeglefinus)皮对鱼糜凝胶特性和蛋白质结构的影响。方法以傅里叶变换红外光谱法和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳技术的分析方法,探究黑线鳕鱼皮不同添加比率对鱼糜凝胶的凝胶强度、质构、持水性、p H和蛋白质分子组成及其二级结构的影响规律。结果 当鱼皮添加比率为5%时,混合凝胶的凝胶强度、弹性和持水性虽下降但无显著变化(P>0.05),分别为2654.4 g·mm、2.83 mm和85.7%,而硬度显著下降至22.83 N (P<0.05);随着鱼皮添加比率的增加,鱼糜凝胶的凝胶强度、质构、持水性均下降;鱼皮的添加阻碍了肌球蛋白重链发生交联,同时,鱼糜凝胶蛋白质结构无显著变化(P>0.05)。结论为提高鱼皮的利用率,可适量将鱼皮与鱼糜混合制备鱼糜凝胶,鱼皮添加比率不宜超过5%。     

Color improvement by titanium dioxide and its effect on gelation and texture of proteins recovered from whole fish using isoelectric solubilization/precipitation

Whiteness is a critical attribute for restructured fish products such as surimi seafood. However, the whiteness of gels made from proteins recovered from fish processing by-products or whole fish using isoelectric solubilization/precipitation is poor. The by-products and whole fish contain bones, scales, skin, etc. that affect gel color. Therefore, whiteness needs to be improved if marketable products are to be developed from recovered proteins. The objectives of this study were to determine effects of titanium dioxide (TiO₂) on: (1) color; (2) texture; and (3) viscoelasticity (G′) of gels made from isolated carp proteins and Alaska pollock surimi. Carp proteins were recovered with isoelectric solubilization/precipitation. TiO₂ was added to carp proteins at 0-0.5 g/100 g. TiO₂ was not added to surimi. Due to much higher (P < 0.05) yellowness (b^∗) and lower (P < 0.05) lightness (L^∗), the whiteness of carp gels without TiO₂ was lower (P < 0.05) than surimi gels. TiO₂ at ≥ 0.2 g/100 g resulted in better (P < 0.05) whiteness of carp gels than surimi gels without chalky and artificially white appearance. TiO₂ did not affect texture or viscoelasticity. This research demonstrates that whiteness of restructured fish products based on proteins recovered from whole fish via isoelectric solubilization/precipitation can be similar to the whiteness of surimi seafood.     

Characterization of Thermorheological Behavior of Alaska Pollock and Pacific Whiting Surimi

ABSTRACT: Thermorheological behavior of Alaska pollock (AP) and Pacific whiting (PW) surimi was evaluated during gelation at different moisture contents (80% to 95%). The temperature sweep data (storage modulus, G', compared with temperature) for both surimi clearly indicated G' minima. Unlike for the PW surimi, the minimum values of the AP surimi was moisture-content dependent and there was a linear relationship between logarithm of concentration and reciprocal absolute temperature at gelation. The activation energy ( Ea ) for aggregation after gelation temperature at each moisture content was calculated by a nonisothermal kinetic model for both AP and PW Surimi. The Ea values increased with moisture content of the system and ranged from 172.8 to 232.9 kJ/mol. Based on the assumption that melting temperature for a thermo-reversible gel may be considered equivalent to gelation temperature for thermo-irreversible gels, an Arrhenius-type model was used to estimate the enthalpy of cross-links formation for AP surimi to be 300.3 kJ/mol.     

Rheological changes during thermal gelation of meat batters containing surimi from alaska pollack (Theragra chalcogramma) or sardine (Sardina pilchardus)

The objective of this study was to use a thermal scanning rigidity monitor to analyse the changes occurring in rheological behaviour during thermal gelation induced by the presence of surimi in meat batters. These studies were conducted on systems prepared with pork meat to which varying proportions of surimi from Alaska pollack (Theragra chalcogramma (Pallas)) or sardine (Sardina pilchardus) (Walb) were added. The results indicated that gelation in pork proteins did not occur in the same way as in fish proteins. Whereas the addition of Alaska pollack surimi to the meat preparations produced scarcely any change with respect to the meat alone, the sardine surimi caused major alterations. These changes depended upon the proportion of protein from surimi added: addition of 100 g kg^?1 caused a protein matrix to form, inducing the formation of stiffer gels and the appearance of the setting phenomenon, although at higher temperatures than are found with fish proteins. Such behaviour was not apparent when the proportion of protein from surimi was raised to 200 g kg^?1.     

Effect of rainbow trout (Oncorhynchus mykiss) plasma protein on the gelation of Alaska pollock (Theragra chalcogramma) Surimi

ABSTRACT:  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 β-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.     

CHITOSAN AFFECTS TRANSGLUTAMINASE-INDUCED SURIMI GELATION

Effect of chitosan on barred garfish (Hemiramphus far) surimi gel was studied in the presence of EDTA and microbial transglutaminase (MTGase). An increase in breaking force of surimi gels added with 1.0% prawn shell chitosan indicated the gel enhancing effect of chitosan on the heat‐induced gelation of fish myofibrillar proteins. However, gel‐forming ability of surimi containing chitosan was inhibited in the presence of EDTA, especially at higher concentration. Therefore, the enhancing effect of chitosan was possibly mediated through the action of endogenous transglutaminase (TGase) during setting, resulting in the formation of protein‐protein and protein‐chitosan conjugates. In general, addition of MTGase remarkably increased both breaking force and deformation of surimi gel (P<0.05). However, enhancing effect of MTGase was retarded in the presence of chitosan, resulting in lower magnitude of breaking force and deformation (P<0.05). Scanning electron microscopy showed that chitosan particles were uniformly dispersed in the gel matrix. A tightly associated gel network was formed in surimi containing MTGase, whereas a large number of voids were noted in gels with EDTA. These results suggest that chitosan acted as a surimi gel enhancer in combination with endogenous TGase in fish muscle, but hindered gel formation in the presence of MTGase.     

高脱乙酰度魔芋葡甘聚糖对鲢鱼鱼糜凝胶特性的影响

本研究探讨了高脱乙酰度魔芋葡甘聚糖(KGM)对鲢鱼鱼糜凝胶特性的影响。将不同添加量0.5 wt%、1.0 wt%、1.5wt%的高脱乙酰度KGM分别添加到鱼糜中,测定其流变、质构特性、持水性、弛豫时间T2及微观结构的变化。发现复合鱼糜的弹性模量G'和损耗模量G"均比纯鱼糜高,且随添加量的增加呈上升趋势,且与纯鱼糜相比,G'和G"最大分别提高了27.98%和49.24%;复合鱼糜的硬度、粘度和咀嚼性比纯鱼糜显著性提高,最大分别提高了10.70%、10.53%和9.52%,但弹性降低;通过低场核磁共振发现,与纯鱼糜相比,复合鱼糜凝胶中T_(22)峰高下降,T_(23)的峰比例上升;复合鱼糜凝胶的持水性总体呈下降趋势,在添加0.5wt%KGM时最低;扫描电镜结果显示复合鱼糜凝胶的网络结构变得更加完整有序。高脱乙酰度KGM影响了蛋白热聚集行为,促进蛋白分子的相互交联,改善了其凝胶网络结构,从而改变了鱼糜凝胶特性。     

乳化鱼油对冻藏期间狭鳕鱼糜热凝胶持水性和冰结晶形成的影响

评估乳化鱼油对冻藏期间狭鳕鱼糜热凝胶持水性和冰结晶形成的影响。鱼糜经盐擂后,加入5%鱼油经乳化制得乳化鱼糜热凝胶。随后用快速冻结和慢速冻结2 种方式冻结样品并评估其在冻藏期间热凝胶品质的变化。研究结果表明：与对照相比,乳化热凝胶在冻藏期间的解冻损失和压榨损失均有降低。显微观察结果显示经3 个月冻藏后乳化热凝胶内的冰结晶平均粒径与其对照相比均有减小,其中快速冻结乳化样品为7.2 μm,对照样品为13.1 μm,慢速冻结乳化样品为13.7 μm,对照样品为31.2 μm。以上结果表明乳化鱼油可能对冻藏期间的热凝胶的冰结晶形成和其分布的影响而导致其持水性不同。     

不同种类淀粉对罗非鱼鱼糜凝胶品质的影响

为了改善淡水鱼鱼糜制品的品质,以冷冻罗非鱼鱼糜为原料,分别添加4%木薯原淀粉、3种木薯变性淀粉（磷酸酯淀粉、羟丙基淀粉和乙酰化二淀粉磷酸酯）及复配木薯变性淀粉（乙酰化二淀粉磷酸酯与羟丙基淀粉质量比为3∶2）,考察淀粉添加对鱼糜凝胶质构、流变学特性、持水性及水分分布和微观结构等的影响,探讨不同种类淀粉对鱼糜凝胶品质的改善。结果表明,与对照组相比,添加5种淀粉均会显著降低罗非鱼鱼糜凝胶的白度（P<0.05）,但其凝胶强度、硬度和咀嚼性显著增大,凝胶持水性显著提高（P<0.05）,蒸煮损失率显著下降（P<0.05）,结合水含量显著增加（P<0.05）,凝胶微观结构更加均匀致密,且添加了复配木薯变性淀粉的凝胶质构特性最好,持水性最高。低场核磁共振成像和光学显微镜观察结果显示,不同种类的淀粉均能有效锁住鱼糜凝胶基质中的水分;升温过程中淀粉吸水膨胀,在鱼糜凝胶网络结构中起浓缩和填充作用;添加了复配木薯变性淀粉的鱼糜凝胶结构最致密均匀。因此,添加复配木薯变性淀粉可以有效改善罗非鱼鱼糜制品的品质,为淡水鱼鱼糜制品的开发提供了理论支撑。     

Rheological studies on specific ion forms of ι-carrageenate gels

Measurements have been made of the shear modulus for calcium, potassium and sodium ι-carrageenate gels as a function of biopolymer concentration and temperature. The results are discussed in terms of the application of rubber elasticity theory. Calcium ι-carrageenate gels appear to possess a random glass-like structure whereas both sodium and potassium ι-carrageenate gels form a pseudocrystalline structure. These differences are tentatively attributed to differences in the solubility of the salt forms which, through controlling the gelation temperature, moderate the kinetics of the gelation process.     

超高压对鲤鱼肉糜-MgCl2凝胶特性的影响

为研究超高压对低盐鲤鱼肉糜凝胶品质的影响,本文在低盐条件下（2% NaCl）,探讨了不同压力超高压处理（100~400 MPa）对含有0.3%氯化镁（MgCl₂）鲤鱼肉糜凝胶的蒸煮得率、保水性、色泽、质构、凝胶强度和流变学特性的改善作用。结果表明:适当的压力处理结合MgCl₂可以显著提高鲤鱼肉糜的凝胶品质。当处理压力为200 MPa时,鲤鱼肉糜凝胶的蒸煮得率、保水性、硬度、凝胶强度均达到最大值,分别为93.14%、95.24%、3327.25 g、3277 g。与对照组相比,适当的压力处理可以显著改善鲤鱼肉糜-MgCl₂凝胶的储能模量（G'）,同时对产品的色泽影响较小。因此,超高压结合氯化镁可以改善低盐鲤鱼鱼糜凝胶的品质,为低盐淡水鱼糜制品的开发提供理论依据。     

Changes of water state and gel characteristics of Hairtail (Trichiurus lepturus) surimi during thermal processing

This study examined the changes of water state and gel characteristics of Hairtail surimi during thermal processing including two steps. The results showed that there were four content of water in Hairtail surimi gels. Water‐holding capacity (WHC) and T₂₃ relaxation time of water and gel strength increased from 47.01 to 78.97% and from 64.23 to 51.52 ms, respectively, and whiteness decreased from 63.87 to 55.22 during the entire thermal processing. Meanwhile, the texture properties including hardness, gumminess, and chewiness declined from 402.42 to 130.41 g, from 294.39 to103.70 g, and from 233.68 to 43.60 g, respectively, during the first step, and then increased markedly during the second step from 130.41 to 2,301.87 g, from 103.70 to 1,250.99 g, and from 43.60 to 978.51 g, respectively. Furthermore, the WHC and textural profile had positive correlation, and changes in protein secondary structure were interesting, with the α‐helices decreasing significantly from 26.40 to 14.12%, while the β‐sheet and the random coil structure increasing significantly from 36.28 to 44.03%, and from 10.89 to 14.31%, respectively, and β‐turn structure increasing form 26.44 to 27.98% during the first step and then declining markedly during the second step, moreover β‐sheet had a fine positive correlation with WHC hardness and chewiness. Overall, dense, porous and compact three‐dimensional network gel structure gradually formed. In a word, during thermal processing. WHC of Hairtail surimi increased, and protein secondary structure of protein became orderly, and a fine, dense gel formed during thermal processing. Water is considered as the highest and most important chemical constituent in surimi products. During surimi gelation, water molecules exist as bulk water and motionally restricted water on the protein surface. In order to gain more insights into the surimi heating‐induced gelation processing, and improve the surimi gel properties, and give same advice to manufacturing enterprise, this work was conducted to study the structural changes of protein and water state during surimi gelation processing and performed along with the monitoring of the texture, WHC and other physical characteristics of surimi gel, as well as the microstructure of surimi gel.     

Effects of CaCl<Subscript>2</Subscript> on chemical interactions and gel properties of surimi gels from two species of carps

Effects of CaCl₂ on chemical interactions, textural properties and expressible moisture content of suwari and kamaboko gels from yellowcheek carp and grass carp were investigated. And the correlations between the contents of chemical interactions and physical properties of surimi gels were analyzed. The contents of chemical interactions, especially non-disulfide covalent bonds, disulfide bonds and hydrophobic interactions of suwari and kamaboko gels, varied with addition concentration of CaCl₂ and fish species. Suwari and kamaboko gels from yellowcheek carp exhibited higher breaking force, deformation and gel strength than these from grass carp. Surimi gels (suwari and kamaboko gels) from yellowcheek carp and grass carp exhibited their maximum gel strength when 40 mmol/kg and 100 mmol/kg CaCl₂ was added, respectively. Addition of CaCl₂ at high concentration resulted in low water holding capacity of surimi gels. Correlation analysis indicated that the contents of nonspecific associations, ionic bonds, hydrophobic interactions and sulfhydryl groups exhibited significant correlation with breaking force of surimi gels from yellowcheek carp and grass carp. Additionally, the content of non-disulfide covalent bonds had significant positive correlations with breaking force and expressible moisture of surimi gel from yellowcheek carp.     

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.     

酸碱法提取鲢鱼肌肉蛋白的胶凝特性

采用酸碱法(pH-shifting)提取鲢鱼肌肉蛋白,并研究不同工艺提取的鱼糜蛋白的胶凝特性。结果表明：与水洗鱼糜相比,酸提蛋白的肌球蛋白重链明显降解,肌动蛋白含量减少;碱提蛋白的肌动蛋白含量最高,加热胶凝造成碱提蛋白的肌球蛋白重链部分降解;酸碱提取蛋白胶凝温度和储能模量(G＇)降低;酸提蛋白胶凝热损失显著高于水洗鱼糜凝胶和碱提蛋白,但水洗鱼糜凝胶和碱提蛋白胶凝热损失之间没有显著差异(P＜0.05);酸提蛋白和碱提蛋白凝胶的保水性显著低于水洗鱼糜凝胶(P＜0.05);酸提蛋白凝胶的凝胶强度最低(46.81N×mm),但碱提蛋白凝胶(60.59N×mm)和水洗鱼糜凝胶(63.57N×mm)的强度之间没有显著差异(P＜0.05)。碱法是提取鲢鱼肌肉蛋白的合适方法。     

Investigation of sweet potato starch as a structural enhancer for three‐dimensional printing of Scomberomorus niphonius surimi

Three‐dimensional printing (3DP) of surimi requires a structural modifier to achieve a stable construct. This work investigated the effect of addition of sweet potato starch (0–10% wt/wt) on the physical properties (rheological properties, gel strength, water‐holding capacity [WHC], and microstructural characteristics) of surimi gels and the 3D printed behavior of these gels. The results showed that as the starch content increased, the viscosity of the starch–surimi mixture decreased facilitating the flow of the surimi out of the printer nozzle. The surimi gel with 8% sweet potato starch concentration showed good gel strength (2,021.70 g mm), WHC (82.39%), microstructural characteristics, and less cooking loss (1.95%). A comparison of the traditional surimi preparation method with 3DP showed that the surimi gel prepared by a 3D printed construct was softer in gel strength (1,398.65 g mm) and lower in hardness (945.17 g) although showing slightly higher cooking loss (6.76%) and lower WHC (72.66 g) than the conventional product. The results suggest that sweet potato starch can be effectively used as a structural enhancer for 3DP complex‐shaped surimi.     

Physicochemical changes in surimi with salt substitute

Protein endothermic transitions (thermal denaturation), rheological properties (protein gelation), and fundamental texture properties (shear stress and strain at mechanical fracture) of Alaska pollock surimi gels made with 0 (control), 1, 2, and 3 g/100 g of salt (NaCl) were determined and compared with equal molar concentration of salt substitute. Salt and salt substitute shifted the onset of myosin transition to higher temperature and resulted in larger myosin peaks (i.e., transition enthalpy). Endothermic transitions showed similar trends to rheological properties. The elastic modulus (G′) increased when salt or salt substitute was added to surimi, except at the highest concentration of salt and salt substitute. Salt and salt substitute also induced the onset of protein gelation (i.e., as measured by significant increase of G′) at lower temperature. Surimi gels with salt substitute and salt at equal molar concentrations had similar texture properties (shear stress and strain). Based on the present study, salt substitute can be used in the development of low-sodium surimi seafood products without significant change in gelation and texture.