Total activity of transglutaminase at various temperatures in several fish meats

ABSTRACT: Transglutaminase seems to be related to the setting phenomenon of fish meat paste that occurs at temperatures below 40°C. In many reports on the relationship between transglutaminase and setting phenomenon, the enzyme activity has been measured at 25°C. However, it is known that the setting phenomenon is complicated and the effect of calcium and the 3-D structure of myofibrils, which are sensitive to temperature, play important roles in the reaction. In the present study, total activities of transglutaminase of threadfin bream, white croaker, red sea bream and carp meats were measured at various temperatures. Total transglutaminase activities at 25°C of tested fish meats are arranged in order as follows; white croaker, red sea bream, carp, threadfin bream. In contrast, optimal temperature of carp meat is 30°C, red sea bream 40°C, threadfin bream 50°C and white croaker 50–55°C. In carp meat, the enzyme activity at optimal temperature (30°C) became 8.5-fold higher than at 25°C. The data of the total activity at various temperatures are useful in order to comprehend the details of the reaction.     

Quality Characteristics of Tilapia Surimi: Effect of Single Washing Cycle and Different Washing Media

Surimi was prepared by washing with single washing cycle with cold water (T-1), alkaline saline (0.2% NaHCO₃ and 0.15% NaCl; T-2) solution, and with calcium chloride and salt (0.2% CaCl₂ and 0.1% NaCl; T-3), respectively, and compared with conventional washed (CW) surimi. T-2 exhibited significantly (p ≤ 0.05) increased moisture content, which correlated with increased yield, pH and also significantly decreased lipid and ash content. A significant (p ≤ 0.05) decrease in expressible moisture content was also observed in T-2, which suggested higher water holding capacity compared to other treatments. Heat-induced surimi gels exhibited highest L* (p ≤ 0.05), followed by surimi in all the treatments. In the case of L*, T-1 showed highest lightness, followed by T-2, which was comparable to CW. The lowest myoglobin content was exhibited by CW surimi (p ≤ 0.05), which is due to repeated washings. T-2 gel showed higher elasticity, texture, and overall acceptability than others (p ≤ 0.05), except for the whiteness. In all the aspects, T-2 was comparable with CW. Washing with one cycle of T-2 solution can not only improve the quality of surimi but can reduce the wastage of water that is released into the environment without further treatment.     

鲐鱼肉酶解物添加量对带鱼鱼糜蛋白抗冻效果的影响

为了提高冷冻带鱼鱼糜的抗冻能力,本试验以肌原纤维蛋白溶解度、Ca2+-ATPase活性、活性巯基含量以及鱼糜保水性为指标,研究鲐鱼肉酶解物添加量对冻藏带鱼鱼糜抗冷冻变性效果的影响,以确定鲐鱼肉酶解物合适的添加剂量.结果表明,随着酶解物添加量的增加,带鱼鱼糜蛋白的抗冻能力随之增加,但添加量达到5％后,随着酶解物剂量的增加,抗冻能力增强幅度变小,鲐鱼肉酶解物合适的添加量为5％ ～7％.综上所述,添加5％ ～7％鲐鱼肉酶解物,能有效抑制带鱼鱼糜肌原纤维蛋白的冷冻变性,提高鱼糜保水性,鲐鱼肉酶解物有望成为良好的鱼糜抗冻剂.     

淡水鱼丸的加工工艺研究

以白鲢为主要原料,研制和加工鱼丸产品。通过对鱼丸的感官特性综合评定,初步确定了鱼丸的最佳加工工艺和配方。     

魔芋葡甘聚糖凝胶体系对带鱼鱼糜流变及质构特性的影响

为了改善带鱼鱼糜凝胶特性,采用流变仪、质构仪等方法研究了魔芋葡甘聚糖凝胶体系对带鱼鱼糜凝胶特性的影响.实验结果表明,在振动频率范围内,带鱼-KGM鱼糜复合凝胶体系的储能模量G ′＞损耗模量G″,表现为弹性为主的稳定凝胶体系;在加热过程中,复合鱼糜的G′和G″经历了3个阶段的变化.同时在升降温过程中,适当改善复合鱼糜体系的pH值,体系的G ′和G″明显增加.添加KGM凝胶体系能够提高带鱼鱼糜的凝胶强度和持水性,其体系的pH值为9.7±0.1时,鱼糜的凝胶强度最大(576.672±10.653 g·cm)和持水性最强(93.672％±0.654％),之后随着pH值的升高,凝胶强度及持水性有所下降,但仍高于空白对照组.添加KGM凝胶体系影响带鱼鱼糜的白度,在pH值为6.4±0.1时能够改善复合鱼糜的白度,之后随着pH值的上升,复合鱼糜的白度呈下降趋势.     

壳聚糖絮凝回收分级等电沉淀后鱼糜漂洗水中蛋白质

为实现鱼糜漂洗水中蛋白质的洁净回收,同时达到净化鱼糜漂洗水及提高资源利用率的目的,该文针对分级等电沉淀回收蛋白质之后的低蛋白浓度废水,研究了蛋白-壳聚糖絮凝过程,探索了主要动力学和热力学因素对絮凝过程的影响;并根据Box-Benhnken设计进行了优化试验。结果表明,狭鳕鱼鱼糜漂洗水中蛋白质等电点主要集中在4.30和5.50,分级回收后蛋白质的回收率达到77.7%。其中絮凝时间、壳聚糖用量和脱乙酰度、絮凝温度和p H值对壳聚糖絮凝蛋白质均有影响,而絮凝温度的影响更多体现在50℃以上的较高温度区域。根据响应面分析结果,在脱乙酰度95%,反应时间90 min,p H值8.04,壳聚糖用量369 mg/L,温度19.6℃的条件下,可获得94.75%的蛋白总回收率,废水中蛋白质量浓度降至0.37 mg/m L以下。研究结果为富蛋白生产废水处理提供了技术参考。     

升温速率对草鱼和鲢鱼糜胶凝特性的影响

以鲢(Hypophthalmichthys molitrix)和草鱼(Ctenopharyngodon idellus)为试验材料,采用动态流变仪研究加热速率对草鱼和鲢鱼糜动态流变性质的影响,并根据非等温动力学模型计算出鱼糜凝胶的凝胶化温度和凝胶活化能。结果表明:在本试验研究的加热速率范围内,随着加热速率的增加,草鱼和鲢鱼糜的弹性模量(G′)和耗能模量(G″)均呈降低趋势,而损耗角正切值(tanδ)则呈增加趋势。增加加热速率使得草鱼和白鲢鱼糜的凝胶化温度(tgel)升高,凝胶活化能(Ea)下降。同一加热速率下,草鱼的凝胶化温度高于鲢,但凝胶活化能低于鲢。     

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.     

超高压处理对大黄鱼鱼糜水分状态和蛋白质结构的影响

为了研究超高压处理大黄鱼鱼糜的凝胶特性,该文利用低场核磁共振、拉曼光谱研究了水浴加热和超高压处理鱼糜凝胶化过程中水分存在状态和蛋白质结构的变化,并分析了它们和鱼糜凝胶特性指标的相关性。结果表明,与水浴加热处理相比,超高压处理能改善鱼糜凝胶特性,使其保水率、弹性、内聚性增大（P<0.05）,硬度下降（P<0.05）。但随压力增大,鱼糜的内聚性、弹性、咀嚼性呈下降趋势（P<0.05）,保水率变化不显著（P>0.05）;低场核磁共振分析显示超高压使鱼糜自由水组分消失,不易流动水的流动性增强（P<0.05）,结合水的含量增加（P<0.05）;拉曼光谱分析显示超高压使鱼糜蛋白α-螺旋含量显著增加（P<0.05）,无规卷曲和β-转角含量显著下降（P<0.05）,三级结构也发生变化;相关性分析表明,蛋白质结构、水分状态及含量与鱼糜的质构、保水率之间存在特定相关性。说明不同处理条件下,鱼糜的蛋白质结构和水分状态发生改变,从而表现出相应的质构、保水率等凝胶特性。以上结果可为鱼糜凝胶特性的评价及改进提供检测方法及理论依据。     

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.