不同多糖对冻藏过程中草鱼肌原纤维蛋白流变性的影响

以草鱼肌原纤维蛋白作为研究对象,添加魔芋葡甘聚糖降解产物及葡聚糖（7 000 D,T7）,测定草鱼肌原纤维蛋白质量浓度、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gelelectrophoresis,SDS-PAGE）和流变性质的变化,比较不同多糖对冻藏过程中肌原纤维蛋白的冷冻保护效果,探讨不同多糖对草鱼肌原纤维蛋白结构的冷冻保护机制。研究发现,随冻藏时间的延长,空白、酶解魔芋葡甘聚糖、辐解魔芋葡甘聚糖、T7及商业抗冻剂各组对应草鱼肌原纤维蛋白质量浓度和流变储能模量（G’）均下降,与冻藏过程草鱼肌原纤维蛋白SDS-PAGE的变化基本吻合。同时,添加上述不同多糖各组草鱼肌原纤维蛋白质量浓度和G’均高于空白组。研究结果表明：T7、酶解魔芋葡甘聚糖及辐解魔芋葡甘聚糖通过保护副肌球蛋白和肌球蛋白轻链,延缓草鱼肌原纤维蛋白的变性,其中,辐解魔芋葡甘聚糖效果最强,T7次之,酶解魔芋葡甘聚糖最弱,但都具有明显的冷冻保护作用。     

刺云实胶对草鱼肌原纤维蛋白的冷冻保护作用

为探究刺云实胶对肌原纤维蛋白的冷冻保护作用,以商业抗冻剂(4%蔗糖+4%山梨醇)为对照,研究刺云实胶对草鱼肌原纤维蛋白溶液冻结曲线的影响,并通过测定0～28 d冻藏过程(-20±1℃)中肌原纤维蛋白Ca²⁺-ATPase活性、巯基含量、表面疏水性、内源性荧光光谱及解冻后水分流动性的变化来研究刺云实胶对草鱼肌原纤维蛋白冻藏稳定性的影响。结果表明,添加1.0%刺云实胶和商业抗冻剂的草鱼肌原纤维蛋白溶液的冻结点分别为-8.3℃和-7.3℃,低于空白样品的-5.5℃。与新鲜肌原纤维蛋白相比,冻藏28 d后,添加1%刺云实胶和商业抗冻剂的肌原纤维蛋白的Ca²⁺-ATPase活性、总巯基含量、活性巯基含量分别下降了45.69%和45.17%、24.49%和42.28%、25.13%和39.79%,而表面疏水性分别增加了176.00%和122.23%,变化幅度显著低于空白对照组。低场核磁共振分析研究结果表明添加1%刺云实胶和商业抗冻剂可以显著抑制肌原纤维蛋白溶液解冻后水分流动性增加。因此,1%刺云实胶可以增强冻藏过程中草鱼肌原纤维蛋白的稳定性。     

聚葡萄糖对冻藏鳙鱼鱼糜抗冻作用的研究

本文以Ca2+-ATP酶活性、肌原纤维蛋白溶出量、总巯基含量、二磺键含量、表面疏水性、水结合能力等的变化(WHC)为指标,研究了聚葡萄糖在4％、8％水平上对鳙鱼鱼糜蛋白在-18℃冻藏10周的抗冻作用,并与传统的商业抗冻剂(4％蔗糖+4％山梨醇)进行比较.结果表明:4％聚葡萄糖具有显著的抗冻作用,可与商业抗冻剂相比拟,而...     

冻藏条件下魔芋葡甘聚糖降解产物对肌原纤维蛋白结构的影响

为了研究魔芋降解产物对肌原纤维蛋白冷冻保护的作用机制,以草鱼肌原纤维为研究对象,采用紫外光谱、傅里叶红外光谱和扫描电镜研究不同的魔芋葡甘聚糖（konjac glucomannan,KGM）降解产物对冷冻贮藏草鱼肌原纤维蛋白结构的影响。结果表明：随着贮藏时间的延长,肌原纤维蛋白的最大吸收波长呈红移,主要由酪氨酸产生,不同的冷冻保护剂均不能保护酪氨酸的暴露。α-螺旋和β-折叠为草鱼肌原纤维蛋白主要的二级结构,随着贮藏时间的延长,α-螺旋结构所占比例上升,β-折叠结构所占比例下降,β-转角和无规卷曲的含量变化不大。辐照降解KGM和酶解KGM均对草鱼肌原纤维蛋白的二级结构有保护作用,稳定α-螺旋和β-折叠所占比例;而蔗糖-山梨糖醇促进草鱼肌原纤维蛋白中α-螺旋结构形成,不利于β-转角结构。显微观察的结果显示,辐照KGM样品和酶解的KGM样品可以延缓蛋白分子的聚集,延缓蛋白出现多孔状结构,而蔗糖-山梨糖醇样品冻藏过程保持片层结构。     

菊粉对冻藏鲢鱼鱼糜肌原纤维蛋白抗冻性的影响

研究菊粉对冻藏鲢鱼鱼糜肌原纤维蛋白抗冻性的影响,对鲢鱼鱼糜盐溶性蛋白含量、肌原纤维蛋白的Ca2＋-ATPase活性、总巯基含量、活性巯基含量、表面疏水性进行分析。结果表明,在－18 ℃条件下冻藏5 周后,菊粉可以抑制鲢鱼糜肌原纤维蛋白的冷冻变性,盐溶性蛋白含量、肌原纤维蛋白的Ca2＋-ATPase活性、总巯基含量、活性巯基含量的下降趋势和表面疏水性的增加趋势均得到抑制,其中1.5%菊粉的抗冻效果优于其他实验组且与商业抗冻剂接近。研究结果为开发热量和甜度较低的抗冻剂提供一定的理论依据。     

Cryoprotective effects of trehalose and sodium lactate on tilapia (Sarotherodon nilotica) surimi during frozen storage

The cryoprotective effects of trehalose and sodium lactate at level of 8% (w/w) in tilapia surimi were studied in comparison with a conventional cryoprotectant (sucrose/sorbitol, 1:1) during extended storage at −18 °C for up to 24 weeks. All present cryoprotectants retarded the protein changes as evidenced by the lowered decrease in salt extractable protein (SEP), Ca²⁺-ATPase activity, total sulfhydryl content as well as the impeded increase in disulfide bond content and surface hydrophobicity. The gel-forming ability of frozen surimi was more retained with addition of cryoprotectants. Among all cryoprotectants used, trehalose exhibited the greatest protective effect on protein denaturation as shown by the effectiveness in maintaining Ca²⁺-ATPase activity and protein solubility. Additionally, the greatest breaking force and deformation were obtained in surimi added with 8% trehalose throughout the frozen storage up to 24 weeks. Sodium lactate showed a similar cryoprotective effect to sucrose/sorbitol blend. Therefore, trehalose and sodium lactate appeared to be promising alternative cryoprotectants for surimi owing to their low sweetness and caloric value.     

葡聚糖延缓草鱼肌原纤维蛋白冷冻变性的机理分析

以草鱼肌原纤维蛋白为研究对象,通过研究盐溶性蛋白质量浓度、Ca2＋-ATPase活性、表面疏水性、总巯基和活性巯基含量在冷冻贮藏条件下的变化,比较不同分子质量葡聚糖（添加量0.5%）和传统商业抗冻剂（4%蔗糖＋4%山梨糖醇）对冻藏过程中肌原纤维蛋白的冷冻保护效果。结果表明,在冻藏过程中,葡聚糖能有效延缓草鱼肌原纤维蛋白的冷冻变性,效果优于传统商业抗冻剂;分子质量小的葡聚糖（T7）对Ca2＋-ATPase活性和活性巯基的保护作用要整体优于分子质量大的葡聚糖（T20）,冻藏超过15 d后延缓表面疏水性的上升和总巯基的保护上的效果也显著优于后者;因此,在工业中选用分子质量小的葡聚糖作为淡水鱼及相关制品的冷冻保护剂效果更佳。     

Effects of rice residue on physicochemical properties of silver carp surimi gels

The objective of this study was to determine the effects of rice residue on the physicochemical properties of silver carp surimi gels. The whiteness of gels was slightly decreased when rice residue was added. Breaking force and deformation of gels were significantly decreased with more than 1% rice residue addition (p < 0.05). The trends of storage modulus, tan δ, and interactions demonstrated a negative effect of rice residue (more than 1%) on gel network. The addition of rice residue reduced the interactions in surimi gel network, such as hydrophobic interaction. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis indicated that there was little interaction between rice proteins and myofibrillar proteins. Rice residue deteriorated the freeze-thaw stability of surimi gels. Therefore, rice residue could be an inactive filler in the gel network unless it was less than 1%.     

The Cryoprotective Effect of Different Konjac Glucomannan (KGM) Hydrolysates on the Glass Carp (Ctenopharyngodon idella) Myofibrillar During Frozen Storage

The physicochemical properties, Ca²⁺–ATPase activity, and surface hydrophobicity of grass carp myobrillar with different cryoprotectants (0.5 % irradiated degraded KGM, 0.5 % β-glucanase KGM hydrolysate, 8 % sucrose-sorbitol (1:1 w/w)) were investigated. The molecular weight analysis showed that the irradiated degraded KGM and β-glucanase KGM hydrolysate were 1.209?×?10⁴ and 2.093?×?10⁴ Da, respectively. The solubility, Ca²⁺–ATPase activity, and total and reactive sulfhydryl (SH) content of treatments containing KGM hydrolysates were higher than other treatments during frozen storage. Addition of KGM hydrolysates could effectively prevent the increase of surface hydrophobicity. The gel strength and whiteness of surimi showed that the addition of KGM hydrolysates in this experiment resulted in surimi with comparable quality.     

海藻糖、乳酸钠对冻藏鳙鱼鱼糜蛋白抗冻效果的影响

以凝胶强度、盐溶性蛋白含量、Ca~(2+)-ATPase活性、总巯基、表面疏水性为指标并结合DSC分析(差示扫描量热分析),研究了海藻糖、乳酸钠在8%(w/w)水平上对鳙鱼鱼糜蛋白在-18℃冻藏24周的抗冻效果,并将其抗冻效果与传统商业抗冻剂(4%蔗糖+4%山梨糖醇)进行了对比。结果表明,海藻糖、乳酸钠的加入能较好地抑制冻藏鳙鱼鱼糜蛋白的冷冻变性,表现在这2种物质加入后,冻藏鳙鱼鱼糜的凝胶能力得到较好的维持,盐溶性蛋白含量、Ca~(2+)-ATPase活性和巯基含量的下降及表面疏水性的增加也得到很好的抑制,2种物质的抗冻效果比传统商业抗冻剂具有明显的优势。DSC分析表明,抗冻剂的添加可能改变了鳙鱼鱼糜肌球蛋白的结构,使其变得更稳定,从而表现出较好的冻藏稳定性。海藻糖、乳酸钠都属于低甜度、低热值物质,因此在鱼糜加工业中有望成为传统商业抗冻剂的替代物。     

Optimal blending of differently refined fish proteins based on their functional properties

Two different mixtures (Alaska pollock surimi with grass carp fish protein isolate (FPI) and grass carp surimi with grass carp FPI) were investigated for their compatibility and functionalities. As the proportion of FPI increased, it was observed surface hydrophobicity and surface reactive sulfhydryl (SRSH) content increased significantly, indicating the degree of fish protein unfolding prior to gelation was much higher than surimi alone. Comparable results were shown as measured by storage modulus (G′) in oscillatory dynamic rheology, demonstrating the gelling temperature was reduced when the proportion of FPI increased. Effects of mixing surimi and FPI on gel functionality (hardness, cohesiveness, and whiteness) exhibited a linear pattern when the proportion of surimi was larger than or equal to that of FPI. However, there were no linear relationships when the proportion of FPI exceeded that of surimi.

Practical applications

Commercial surimi has been successfully used in the Western world over 30 years. Unlike surimi which is a refined fish myofibrillar protein composite, fish protein isolate (FPI) is a refined composite of myofibrillar protein and sarcoplasmic protein. The former is made by avoiding any chemical/physical denaturation, while the latter can be made by inducing chemical denaturation and renaturation with pH shift. Even though FPI is not currently available in a commercial scale, it has a great potential to replace all or a part of surimi for the manufacture of fish protein gel products. This study reveals how to optimally mixed these two differently refined fish proteins based on their functional properties. The results suggested that blending surimi and FPI may be feasible only when the proportion of FPI does not exceed 50%.     

The effect of low- or non-sweet additives on the stability of protein functional properties of frozen cod surimi

The cryoprotective effect of low- or non-sweet additives, Palatinit^R, Polydextrose^R, casein hydrolysate and fish protein hydrolysate (at 8% w/w) as well as lactitol (at 4% and 8% w/w) were compared to an industrial control containing sucrose/sorbitol (8% w/w) and a control without additive in cod surimi stored at –20°C for 4 months. Freeze-induced protein denaturation was evaluated monthly by salt extractable protein and differential scanning calorimetry analyses of surimi followed by texture and expressible moisture analyses of surimi cooked gels. Results revealed that protein functionality was similarly maintained during frozen storage by lactitol, Palatinit^R and Polydextrose^R when incorporated in cod surimi at the 8% level. Surimi gels could be produced with textural attributes comparable to 8% w/w sucrose/sorbitol surimi gels, and the level of lactitol in cod surimi could be reduced to 4% w/w without significant alteration of cryoprotection. Some benefits in gel-forming properties were obtained by adding 8% casein hydrolysate to cod surimi.     

添加不同物质冻藏对鲤鱼肌肉蛋白功能性的影响

以淡水鱼主要品种鲤鱼为研究对象,研究添加抗冻剂和不同抗氧化剂对鲤鱼肌原纤维蛋白冻藏过程中功能特性的影响。鲤鱼肉糜经漂洗后,分成四组（对照组、添加抗冻剂、添加抗冻剂+没食子酸丙酯（propyl gallate,PG）、添加抗冻剂+乳清蛋白水解肽）后置于?25 ℃,冻藏不同时间（0、30、60、90、120 d）后,利用质构仪、电子显微镜和流变仪等对鲤鱼肌原纤维蛋白乳化性、凝胶性以及流变性等指标进行测定。结果表明,冻藏过程会引起鲤鱼肌原纤维蛋白功能特性降低,表现为肌原纤维蛋白乳化性、凝胶性、流变特性均有所下降,但添加抗冻剂和两种抗氧化剂冻藏后,鱼肉肌原纤维蛋白功能特性下降程度减弱,说明在鱼糜冻藏过程中添加抗冻剂和抗氧化剂可以有效地抑制蛋白质结构发生变化,从而降低肌原纤维蛋白功能特性的劣变。     

鲢鱼与金线鱼混合鱼糜的凝胶特性

为研究鲢鱼与金线鱼混合鱼糜的凝胶特性,本实验对混合鱼糜凝胶的凝胶强度、持水性、蒸煮损失、白度值、横向弛豫时间、微观结构和肌原纤维蛋白进行分析。结果表明：混合鱼糜的白度值较纯金线鱼鱼糜显著提高（P＜0.05）,且鲢鱼鱼糜与金线鱼鱼糜质量比5∶1混合后的凝胶白度值高于纯鲢鱼鱼糜;此配比下的混合鱼糜凝胶性能最好,其中凝胶破断力、凹陷距离、凝胶强度和持水性较鲢鱼鱼糜分别提高了18.33%、27.29%、51.01%和5.65%,较金线鱼鱼糜分别提高了5.84%、19.50%、26.49%和3.45%;该配比下的混合鱼糜凝胶的蒸煮损失较鲢鱼鱼糜和金线鱼鱼糜分别降低了15.88%和7.48%。低场核磁共振分析显示鲢鱼鱼糜与金线鱼鱼糜质量比5∶1混合后的鱼糜凝胶的横向弛豫时间T22比鲢鱼鱼糜凝胶T22缩短了10.34 ms。通过扫描电镜观察发现鲢鱼鱼糜与金线鱼鱼糜质量比5∶1混合时可形成高度均匀、致密的空间凝胶网络结构。肌原纤维蛋白凝胶电泳图显示该配比下肌球蛋白重链（myosin heavy china,MHC）发生交联,大分子聚集体形成,进入凝胶中MHC更少,条带更细窄。     

鲢鱼酶解物对冻融鱼糜制品品质及其蛋白质体外消化率的影响

选择复合蛋白酶水解鲢鱼制酶解产物,以添加了商业抗冻剂(商抗,4%蔗糖+4%山梨醇)的鱼糜制品作对照,综合评价添加了鲢鱼酶解产物的鱼糜制品冻融前后品质及其蛋白质体外消化率的变化。试验结果表明:冻融后,鱼糜制品中添加2%的酶解产物可以增加鱼糜凝胶持水性,降低蒸煮损失,并且不会导致鱼糜制品带上酶解产物本身的淡黄色;同时,2%酶解产物添加组能有效减缓鱼糜制品凝胶强度、硬度和弹性的降低及其蛋白质消化率的下降程度;2%酶解产物添加组在冻融前后感官评分均较高,酶解产物的添加避免了商业抗冻剂给产品带来的明显甜味。研究表明,鲢鱼酶解产物可作为潜在的抗冻剂应用于鱼糜及其制品的工业化生产。     

鱼糜凝胶形成过程中物理化学变化

采用化学法测定鱼糜凝胶形成过程中离子键、氢键、疏水相互作用和二硫键的变化,借助拉曼光谱仪分析草鱼鱼糜凝胶形成过程中鱼糜蛋白质构象的变化,进而研究化学作用力和蛋白质构象对鱼糜凝胶形成的影响。结果表明：在草鱼鱼糜凝胶的形成过程中,离子键、氢键显著减少,疏水相互作用、二硫键和非二硫共价键增加;α- 螺旋结构部分转化为无规卷曲结构。疏水相互作用、二硫键及非二硫共价键是影响凝胶形成的主要作用力,α- 螺旋和无规卷曲是草鱼鱼糜凝胶形成过程中维持鱼糜凝胶稳定结构的主要蛋白质构象。     

Effect of Cryoprotectants on Chemical, Mechanical and Sensorial Characteristics of Spent Laying Hen Surimi

The surimi samples were divided into four groups (C, surimi made from Alaska pollack by water washing with NaCl-free cryoprotectant; T1, made from spent laying hen breast by water washing with NaCl-free cryoprotectant; T2, made from spent laying hen breast by water washing with NaCl and sugar-free cryoprotectant; T3, made from spent laying hen breast by water washing with NaCl-contained cryoprotectant). In proximate compositions, collagen and myofibrillar protein were significantly higher in spent laying hen breast surimi samples (T1, T2, and T3) than Alaska pollack surimi sample (C). Folding test score was significantly higher in T3 in all storage periods. Spent laying hen breast surimi samples (T1, T2, and T3) had higher lighness (L*) and whiteness (W) than Alaska pollack surimi sample (C) in all storage period. In sensory evaluation, T3 showed significantly higher score in all sensory evaluation items. As a result of study, the qualities of T3 are higher than those of other surimi samples.     

两种抗冻剂对罗非鱼鱼糜的凝胶性及抗冻性的影响

以凝胶性能、盐溶性蛋白含量及肌原纤维蛋白Ca2+-ATPase活性的变化为指标,研究了商业抗冻剂(蔗糖/山梨醇)和海藻糖在罗非鱼鱼糜冻藏过程中对蛋白质变性的影响。结果表明,冷藏20周后,添加8%商业抗冻剂和8%海藻糖组鱼糜的破断强度分别比对照高出39.14%和601.11%,凹陷强度分别比对照高出34.14%和39.85%,凝胶强度分别比对照高出36.03%和41.05%,盐溶性蛋白含量分别比对照高出30.00%和38.86%,肌原纤维蛋白Ca2+-ATPase活性分别为下降了67.12%和57.89%,而对照的肌原纤维蛋白Ca2+-ATPase没有活性。结论:添加8%海藻糖比8%商业抗冻剂更能有效抑制罗非鱼鱼糜在冻藏过程中的蛋白质变性,减缓凝胶强度的降低,提高鱼糜制品的质量。     

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。     

Effect of frozen storage on thermal stability of sarcoplasmic protein and myofibrillar protein from common carp (Cyprinus carpio) muscle

Thermal stability of sarcoplasmic protein and myofibrillar protein extracted from fresh and frozen common carp was comparatively studied. Total sulphydryl content (SH) in sarcoplasmic protein solution from 5‐month frozen carp decreased by 19.43% compared with fresh sample. The SDS‐PAGE patterns showed that all the bands of sarcoplasmic protein from frozen‐stored samples were almost invisible at 80 °C. Myofibrillar protein from fresh sample exhibited lower turbidity and surface hydrophobicity and higher Ca²⁺‐ATPase activity and SH content than frozen‐stored sample when heated from 20 to 80 °C. The Ca²⁺‐ATPase activity from fresh (M0), 2 (M2)‐ and 5 (M5)‐month frozen‐stored carp was completely lost at 48, 46 and 46 °C, respectively. When heated to 80 °C, the SH content of myofibrillar solutions in M0, M2 and M5 decreased by 26%, 60% and 70%, respectively. Sarcoplasmic and myofibrillar proteins from frozen carp were more susceptible to aggregate during heating treatment.