乳清蛋白与凝胶化条件对鱼糜凝胶特性的影响

研究了浓缩乳清蛋白(WPC)和凝胶化条件对白姑鱼(Argyrosomus argentatus)鱼糜凝胶品质的影响,检测指标包括破断力、凹陷度、凝胶强度、白度和折曲性能.结果表明:白姑鱼鱼糜最适宜的凝胶化条件为40℃ 60 min.在40℃和50℃凝胶化60 min的条件下,添加的WPC在总蛋白中的蛋白比例为5%和10%时能够使白姑鱼鱼麋凝胶特性增强,并能保持和改善凝胶的弹性,抑制50℃下的凝胶劣化现象.但在30℃凝胶化60 min的条件下,WPC的添加反而会降低鱼糜的凝胶特性与弹性.添加10%的WPC能够显著(P<0.05)提高白姑鱼鱼糜凝胶的白度.     

尼罗罗非鱼鱼糜凝胶特性试验

本文研究尼罗罗非鱼鱼糜的凝胶特性,试验结果表明:尼罗罗非鱼属于难凝胶化也不易凝胶劣化的鱼种,凝胶热稳定性能较好,尼罗罗非鱼较不易冷冻变性,原料的处理方式会影响到鱼糜的凝胶形成能力,漂洗可以提高凝胶强度和白度,添加TGase产生的粘合作用对提高罗非鱼鱼糜弹性很有效.     

淀粉种类对草鱼鱼糜凝胶特性的影响

通过分析草鱼鱼糜流变学特性、草鱼鱼糜凝胶特性等,研究不同种类淀粉的添加对鱼糜凝胶性能的影响。结果表明,添加不同种类淀粉(马铃薯淀粉、玉米淀粉、木薯淀粉、乙酰化二淀粉磷酸酯和醋酸酯淀粉)能不同程度地影响草鱼鱼糜的保水性和凝胶品质,包括硬度、凝胶强度、胶着性以及咀嚼性;流变学结果也表明,适量添加淀粉能有效促进草鱼鱼糜凝胶的形成。其中,添加醋酸脂淀粉对草鱼鱼糜的凝胶特性影响最大,使得草鱼鱼糜凝胶强度、持水性和白度均达到最大值。因此,添加醋酸酯淀粉可以显著改善草鱼鱼糜流变及凝胶特性,有助于淡水鱼高值化利用与产业化升级。     

壳聚糖对鲢鱼糜凝胶特性的影响

将壳聚糖添加到鲢鱼糜制品中,测定鱼糜制品的凝胶强度、全质构(TPA)、失水率和色泽,研究壳聚糖的脱乙酰度(DD)、分子量(MW)以及添加量对鲢鱼糜凝胶特性的影响,采用电镜扫描观察凝胶的微观结构,结果表明,壳聚糖DD对鱼糜制品凝胶特性影响较大,DD为64%时,凝胶强度提高了约34%,失水率减少了29.1%;壳聚糖MW对鱼糜制品的凝胶强度影响小;随着壳聚糖添加量的增加,鱼糜凝胶强度、TPA都有明显的增加,失水率减少(P<0.05),添加1.0%壳聚糖的鱼糜凝胶强度与添加4.0%淀粉的鱼糜凝胶强度相当;微观结构可看出壳聚糖与鱼糜形成网络结构。结果说明壳聚糖是鱼糜制品良好的品质改良剂。     

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。     

变性淀粉对鲢鱼糜冻结速率及凝胶特性的影响

为了比较4种变性淀粉与商业抗冻剂(4%蔗糖+4%山梨醇)对鲢鱼糜在冻结过程(-20、-80℃下静止冻结)中的影响,对冻结速率、冻结相变热特性参数、凝胶强度和持水性能进行了测定。结果表明,鱼糜在-80℃下的冻结速率均显著高于-20℃下;同一冻结温度下,几种添加物均会降低鱼糜的冻结速率及冻结相变焓,而提高冷冻鱼糜凝胶的持水性能,且变性淀粉组的持水性都显著高于商业抗冻剂组(P0.05)。在-80℃冻结时,添加交联酯化淀粉与醋酸酯化淀粉的鱼糜的冻结速率相近,且均显著小于其他组(P0.05)。在2种冻结温度下,醋酸酯化淀粉组的凝胶强度均与商业抗冻剂组无显著性差异,而显著高于其他实验组(P0.05)。研究表明,4%蔗糖+4%醋酸酯化淀粉可有效地防止鱼糜在冻结过程中的品质变化,可代替商业抗冻剂应用在冷冻鱼糜中。     

复合弹性增强剂对梅童鱼糜凝胶强度的影响

以漂洗两次，冷藏1个月和冷藏2个月的冷冻梅童鱼糜为试验原料，添加0．5％和1％的复合弹性增强剂，研究不同添加量及不同加热条件对鱼糜凝胶强度和保水性的影响，结果：添加复合弹性增强剂后，冷冻梅童鱼糜的弹性与对照组相比，破断强度提高6－8倍，凹陷度提高2－3倍，凝胶强度提高10－15倍，以40℃，30min-60min凝胶化条件最为适宜，凝胶化时间过长，游离水析水增加，即鱼糕的保水性下降。     

不同处理条件下鲢鱼糜凝胶水分状态和微观结构的特征

为探讨超高压改善低盐鲢(Hypophthalmichthys molitrix)鱼糜凝胶品质的机制,利用低场核磁共振(low field nuclear magnetic resonance,LF-NMR)、差示扫描量热法(differential scanning calorimeter,DSC)、傅里叶红外光谱(fourier transform infrared spectroscopy,FT-IR)以及扫描电镜分析比较了超高压低盐鱼糜凝胶[300 MPa,1.5%氯化钠(NaCl)]与常压低盐鱼糜凝胶(0.1 MPa,1.5%NaCl)以及常压普通鱼糜凝胶(0.1 MPa,2.5%NaCl)在水分状态和微观结构上的差异。DSC结果表明超高压低盐鱼糜凝胶可冻结水的冰点降低,结合水含量(17.58%)较低盐对照组(10.89%)显著提高;LF-NMR表明超高压低盐鱼糜凝胶弛豫时间T21、T23和T24左移,不易流动水的含量(76.65%)较低盐对照组(67.29%)提高了9.39%;超高压处理能使低盐鱼糜凝胶形成光滑、连续、均匀的三维网络结构。因此,超高压处理(300 MPa,10 min)能够提高低盐鲢鱼糜凝胶结合水含量、改善微观结构。     

鱼糜凝胶过程及影响因素

鱼糜制品在我国、日本以及韩国都有很长的历史,由于它是一种高蛋白质、低胆固醇、低热、低盐食品,所以日益受到消费者的欢迎。鱼糜制品要求有良好的弹性、风味、色泽,其中最主要的是弹性。鱼糜制品的弹性是硬度、伸缩性以及粘性的综合体现,主要取决于鱼糜中蛋白质胶凝的情况。凝胶化是鱼糜制品的技术关键,只有经过充分凝胶化的鱼糜制品才富有弹性,有良好的口感,因此探讨鱼糜凝胶机理对于鱼糜制品的生产有着极其重要的指导意义。一、鱼鹰的制作过程原料鱼十预处理～清洗～采肉十漂洗一脱水～绞肉十精滤十擂清一成型～凝胶一加热十包装…     

超声时间对鲢鱼糜凝胶特性和蛋白结构的影响及相关性

为探究超声预处理对鱼糜凝胶特性的影响,并进一步阐明凝胶特性变化与蛋白二级结构之间的相关性规律,本实验对鲢鱼糜进行超声预处理,探究超声过程中(0～50 min)凝胶强度、色泽、水分分布、微观结构、蛋白分子量以及二级结构的变化。结果显示,超声波处理10 min,鱼糜凝胶强度显著提高,束缚水的能力增强,凝胶网络结构更为致密;但随超声时间的增加,凝胶劣化,不易流动水转变为自由水。凝胶电泳及红外光谱结果显示,随着超声时间增加,鱼糜中蛋白未发生降解或聚集;二级结构中α-螺旋相对含量降低,β-折叠、无规则卷曲和β-转角相对含量增加。通过皮尔逊相关性分析可知,超声预处理促进蛋白质结构展开,更利于鱼糜在加工过程中形成均匀的网络结构,提高凝胶强度以及保水能力。研究表明,适量超声预处理可以通过改变鱼糜蛋白结构,改善鱼糜凝胶特性。本研究可为超声波技术在鱼糜制品加工中的应用提供参考。     

Gel Forming Ability of Tropical Tilapia Surimi as Compared with Alaska Pollock and Pacific Whiting Surimi

Abstract

Setting and thermal treatment effects on texture and color of tropical tilapia surimi gels were compared to Alaska pollock and Pacific whiting gels. Heat treatments that most favored intrinsic gelling factors of a fish species exhibited strong gel formation. Whiteness values increased as total thermal inputs increased, which reflect the increasing opacity of the gels. Pollock gels were generally the strongest and whitest. Tilapia gel quality was generally second to pollock gels, however, in heat treatments using setting temperatures ≥ 40 °C, tilapia gels were comparable (60 °C setting) or superior (40 °C setting) to pollock gels. The optimum heat treatment for tilapia surimi appeared to be a 40° C setting for 1 hr followed by a 90 °C cook for 15 min. SDS-PAGE patterns of gels prepared with 60°C setting followed by 90 °C cooking elucidated the various degree of protein degradation depending upon the species in a descending order of whiting, tilapia, and pollock.     

Improvement of Cold and Thermally Induced Gelation of Giant Squid (Dosidicus gigas) Surimi

Depending on the season of capture, giant squid (Dosidicus gigas) surimi processed by isoelectric precipitation presents low gel strength. Addition of microbial transglutaminase (MTGase) and application of high isostatic pressure (300 MPa) to improve physicochemical properties were assayed for purposes of making “suwari” gels and heated gels for use in restructured products which have a raw or cooked appearance. The physicochemical properties of both pressurized and unpressurized gels induced by application of 30°C/1 h improved when MTGase was added. In contrast, addition of MTGase was less effective in gels subsequently heated at 90°C/30 min after 30°C/1 h. High pressure treatment for 30 min at 300 MPa and 15°C helped to produce gels with better mechanical and water binding properties, whether treated for 30°C/1 h only or for 30°C/1 h plus 30-min heat treatment at 90°C. High pressure treatment also reduced lightness.     

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.     

Effect of Setting Condition on the Gel-Forming Ability of Rohu

To investigate the setting condition of the gel-forming ability of rohu, optimum setting temperature for strong and weak gels of unwashed and washed rohu gel and optimum setting time for maximum proteolytic activity were investigated. Nine setting temperatures were studied for textural properties and trichloroacetic acid (TCA)-soluble peptide contents. Both unwashed gel (UW-gel) and washed gel (W-gel) showed similar optimum setting conditions for producing a strong gel that was set at 40°C for 30 min, followed by heating at 90°C for 20 min. They displayed different optimum setting conditions for weak gel. Weak gel from the degradation of UW-gel and W-gel formed at 65 and 60°C, respectively. The occurrence of protein degradation of W-gels during setting at 60°C suggested that washing did not remove the endogenous protease, and the degradation of unwashed and washed mince was due to water-soluble protease and myofibril-bound protease, respectively. Eight setting times for maximum proteolytic activity were shown by the TCA-soluble peptide contents, accompanying the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) pattern. Both gels had similar results for setting for 120 min.     

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.     

Comparison of horse mackerel and tilapia surimi gel based on rheological and <Superscript>1</Superscript>H NMR relaxation properties

ABSTRACT:   Horse mackerel and tilapia surimi were subjected to six different heat and pressure treatments in order to compare gelation characteristics of easy- and difficult-setting gels, that is, temperature dependence, by observing rheological properties and microscopic molecular mobility. The stress–relaxation and proton spin–spin relaxation time (¹H T ₂) of water were measured for all treated gels. Horse mackerel gel demonstrated higher elasticity, large distribution of the stress–relaxation process, and smaller water ¹H T ₂ than tilapia in both heat and pressure treatments. The water ¹H T ₂ was steeply increased in the pressure treatment at around 294 MPa for both fishes. In contrast, the ¹H T ₂ rarely changed in the heat treatment in spite of the considerable change in rheological properties. From the experimental results, it is considered that the gelation of horse mackerel (easy setting) surimi is induced by highly unfolding and re-aggregation of protein, which contributes to the formation of a strong network structure compared with tilapia in both heat and pressure treatments, and that pressure treatments hardly improve the gel strength of tilapia (difficult setting) surimi. The water ¹H T ₂ measurement was used effectively in order to study gelation characteristics of easy- and difficult-setting fish through observing its molecular dynamics.     

Biochemical Properties of Pelagic Fish Proteins as Affected by Isolation Methods and Gel Properties by Heating Methods

The biochemical and gel properties of Pacific sardine and Pacific mackerel were characterized as affected by preparation and cooking methods. Four to eight times more salt soluble proteins were extracted from water-washed paste than fish protein isolate (FPI) paste. Higher total sulfhydryl content was measured in FPI, indicating the exposure of sulfhydryl groups during alkaline extraction. Comparing gel properties based on two cooking methods (slow and fast), the two pelagic fish proteins performed quite differently. Heating rate did not differentiate between surimi and FPI gels from sardine. However, mackerel exhibited higher texture values when using the fast cooking method, indicating the presence of high levels of proteolytic enzymes. Water-washed surimi gels were whiter than FPI for both species. Water retention ability appeared to be higher with mackerel than sardine, regardless of isolation and cooking method. Sodium dodecyl sulfate polyacrylamide gel eletrophoresis (SDS-PAGE) also supported a difference in processing chemistry and thermal behavior between two methods for protein isolation and cooking, respectively.     

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

ABSTRACT: 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.     

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.     

High Pressure Processing and Water Holding Capacity of Sea Bass Skeletal Muscle

The water holding capacity (WHC) and relationship between protein denaturation and WHC of sea bass skeletal muscle (SBSM) with high pressure (HP) treatment were investigated up to a pressure level of 600 MPa. The results showed that it had the lowest cooking loss (CL) at 200 MPa, and CL value decreased 20.9% compared with 0.1 MPa. Additionally, 400 MPa produced the highest water retention, and 0.1 MPa produced the lowest water retention by low field-nuclear magnetic resonance (LF-NMR). The WHC was related to protein denaturation. Examination of extracted proteins using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and protein solubility indicated that high pressure resulted in protein denaturation; the differential scanning calorimetry (DSC) curve showed the myosin peak reduced significantly at 400 MPa and was eliminated at 600 MPa, while the actin peak was eliminated at 300 MPa; morphology of sarcoplasmic proteins were sponge-like at 200 MPa, which was conducive to enhancing WHC.