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.     

马铃薯淀粉对鲤鱼肌原纤维蛋白功能特性的影响

将马铃薯淀粉（不同添加量0%、1%、2%、3%和4%）添加到鲤鱼肌原纤维蛋白中,通过测定肌原纤维蛋白的浊度、乳化性、凝胶的硬度、弹性、保水性、白度值等指标,较为系统地研究了马铃薯淀粉对鲤鱼肌原纤维蛋白功能特性的影响。结果表明:在温度一定时,淀粉-蛋白复合物的浊度随着马铃薯淀粉添加量的增大而升高;在马铃薯淀粉添加量一定时,淀粉-蛋白复合物的浊度随着温度的升高而升高。随着马铃薯淀粉添加量的增加,乳化活力和乳化稳定性呈先上升后下降后又有所增加的趋势,在马铃薯淀粉添加量为2%和1%时乳化活性和乳化稳定性分别达到最大值25.66m2/g,90.67%。当温度相同时,淀粉-蛋白复合凝胶的硬度和弹性值随着马铃薯淀粉添加量的增大而升高,在80℃条件下,添加了4%淀粉的样品与对照组相比硬度和弹性分别提高了65.85%,20.85%,且效果显著（p<0.05）,而随着马铃薯淀粉添加量的增加,凝胶持水性增大（p<0.05）,最大增加了18.75%,但凝胶的白度值呈现下降趋势。因此添加马铃薯淀粉可以有效改善肌原纤维蛋白的功能特性。      

Physicochemical,micro-structural,and textural properties of different parts from farmed common carp (Cyprinus carpio)

The fish body of cultured common carp (Cyprinus carpio) was divided into six sections, including the upper back, lower back, jaw, chest, belly, and tail. Differences in the physicochemical, micro-structural, and textural properties of different muscle tissues were investigated. The upper and lower back, with high content of protein, low content of fat, high water-holding capacity, and desirable textural properties, was proven to be the most valuable part of common carp from both a nutritional point-of-view and an organoleptic perspective. This could provide a theoretic basis for the comprehensive utilization of freshwater fish.     

羟自由基氧化对鲤鱼肌原纤维蛋白乳化性及凝胶性的影响

研究羟自由基( ·OH)氧化对鲤鱼肌原纤维蛋白乳化性、凝胶质地及凝胶微观结构的影响。采用由FeCl3、抗坏血酸浓度和不同浓度(0～20mmol/L)H2O2组成的 ·OH氧化体系,对鲤鱼肌原纤维蛋白分别氧化1、3、5h后测定蛋白的乳化活力及乳化稳定性,利用质构仪、扫描电镜对凝胶特性和微观结构进行研究。结果表明：蛋白质氧化会引起鲤鱼肌原纤维蛋白乳化性及凝胶性发生改变,表现在乳化活力和乳化稳定性下降,凝胶弹性、硬度、保水性及白度有不同程度的下降,凝胶微观结构遭到破坏。这些蛋白氧化引起的变化说明,蛋白质氧化对鲤鱼肌原纤维蛋白乳化性及凝胶性能有较大的破坏作用。     

冷冻及解冻处理对肌原纤维蛋白理化性质的影响

研究不同的冻结温度（-18 ℃和-50 ℃）和解冻方式（微波解冻、空气解冻及4 ℃解冻）对猪肉肌原纤维蛋白含量和理化特性的影响。结果表明,在不同冻结温度与解冻方式下,肌原纤维蛋白的含量、溶解性、乳化活性、乳化稳定性、起泡性及起泡稳定性均降低,表面疏水性增加。其中,采用-18 ℃冻结,微波解冻处理的肌原纤维蛋白与对照组相比,其溶解性、乳化性、乳化稳定性、起泡性及起泡稳定性分别降低了38.7%、16.5%、28.3%、39.6%和17.3%;采用-50 ℃冻结,4 ℃解冻的蛋白其含量（6.32%）、溶解性（22.05%）、乳化性（7.89 m2/g）、乳化稳定性（32%）、起泡性（30.95%）及起泡稳定性（62.25%）与其他处理对应的各指标相比,理化特性均保持较好。不同的冷冻和解冻条件下,肌原纤维蛋白各指标之间的变化相互关联。     

Changes in physicochemical properties and myofibrillar protein properties in grass carp salted by brining and injection

The aim of this study was to investigate the changes in physicochemical properties and myofibrillar protein properties of grass carp meat during brining and brine injection at 4 °C. The time reached equilibrium was 7 h in brining group and 5 h by injection, where the salt content was about 1.76%. The water content, water holding capacity and yield in injection group (86.59%, 9.18% and 110%, respectively) were higher than brining group (84.76%, 11.47%, and 108%, respectively) at equilibrium point significantly (P < 0.05). This was attributed to the more swollen filament lattices and disordered protein structure in injection group (P < 0.05). The myofibrillar protein structure was compared, including sulphydryl content, surface hydrophobicity, solubility, sodium dodecyl sulphate polyacrylamide gel electrophoresis pattern and secondary structure. The injection group presented the better quality of salted fish meat in shorter time.     

不同盐对鲤鱼肌原纤维蛋白结构和凝胶特性的影响

肌原纤维蛋白是鱼肉中的主要蛋白质,对鱼糜类制品的质量起到关键的作用。文中研究了NaCl、CaCl2和Na4P2O73种盐类及其浓度对鲤鱼肌原纤维蛋白结构特性(表面疏水性、蛋白聚合程度)和凝胶特性(质构、微观结构、蛋白浊度)的影响。结果表明:鲤鱼肌原纤维蛋白的等电点为5.5;3种盐加入肌原纤维蛋白后会引起肌原纤维蛋白发生一定程度的聚集,表面疏水性降低;随着盐浓度的增大,肌原纤维蛋白凝胶硬度、弹性、浊度降低;添加CaCl2比其它盐类更明显降低鱼糜的凝胶硬度、弹性和浊度,且差异性显著(P<0.05);NaCl和Na4P2O7使鱼糜凝胶微观结构更致密、CaCl2使鱼糜凝胶微观结构变得松散。因此,在鲤鱼肌原纤维蛋白中添加NaCl、CaCl和NaPO对鱼糜肌原纤维蛋白结构和凝胶特性均有不同程度的影响。     

超声波处理对猪肉肌原纤维蛋白理化及乳化特性的影响

采用超声波技术对猪肉肌原纤维蛋白(myofibrillar proteins,MP)进行改性处理,研究超声功率(0,80,140,180,200W)对肌原纤维蛋白理化与乳化特性的影响。结果表明,与未经超声处理的肌原纤维蛋白比较,随着超声功率的增加,MP体积等效平均粒径(d4,3)降低,而溶解度、电位绝对值、乳化活性及乳化稳定性均显著升高。超声功率达到180W时,该处理的肌原纤维蛋白制备的乳化液表现出较高的乳化活性和乳化稳定性,乳化稳定性的提高与增加的电位和降低的平均粒径有关,光学显微镜观察发现该乳化液表现出相对较低的油滴大小。相关性分析结果表明,超声功率与d4,3极显著负相关(P≤0.01),与溶解度、电位、乳化活性及乳化稳定性显著正相关(P≤0.05)。     

不同冻结方式对猪肉肌原纤维蛋白乳化与凝胶特性的影响

分别采用空气冻结、浸渍冻结和超声辅助浸渍冻结(ultrasonic-assisted immersion freezing,UIF)猪肉背最长肌,提取肌原纤维蛋白(myofibrillar protein,MP)并分析其乳化活性与乳化稳定性、乳液粒径、流变特性、凝胶强度、蒸煮损失率、水分分布与微观形貌变化,研究不同冻结...     

Inhibition of frozen storage‐induced oxidation and structural changes in myofibril of common carp (Cyprinus carpio) surimi by cryoprotectant and hydrolysed whey protein addition

The objective of the present study was to evaluate the efficacy of combined cryoprotectants (sucrose + sorbitol) and whey protein isolate (WPI) hydrolysates to inhibit protein oxidation and quality loss in common carp (Cyprinus carpio) surimi during frozen storage at ?25 °C. With increasing storage time, the carbonyl content of myofibrillar proteins increased from 4.02 nmolmg^‐1 protein (0 day) to 7.25, 6.31, 5.26 and 4.83 nmol mg^?1 protein (180 days; P < 0.05) for the control and samples with cryoprotectants, with cryoprotectants + WPI hydrolysates and with cryoprotectants + propyl gallate, respectively; protein surface hydrophobicity and turbidity increased in a similar trend, while sulfhydryl content, Ca‐ATPase activity, protein solubility and protein thermal stability decreased (P < 0.05). These results suggest that treatments with combined cryoprotectants and antioxidative WPI hydrolysates offer an effective approach to reducing the extent of protein oxidation in common carp surimi, thereby limiting protein structural changes known to impair texture of surimi products.     

Effects of Agaricus bisporus on gel properties of chicken myofibrillar protein

The gel-forming ability of myofibrillar protein (MP) is highly correlated with the characteristics of emulsified meat products. Incorporation of Agaricus bisporus (Ab) powder into MP gels may enhance its gel properties to facilitate the development of a novel and safe meat product. Therefore, this study investigated the effects of Ab powder on gel strength, water holding capacity (WHC), texture, rheological behaviour, LF-NMR spin–spin relaxation (T₂), microstructure and protein secondary structure of the MP gel system. The results indicated that the gel strength, WHC, G' value and G" value were significantly improved when the addition of Ab powder increased from 0% to 6% (P < 0.05). Meanwhile, the T₂ relaxation time was shortened, and free water was transformed into immobilised water. The texture of the gel was improved when 1%–4% Ab powder was added compared to the control. Furthermore, Ab filled in the gel network and promoted the unfolding of MP α-helix and the formation of MP β-sheet during the thermal denaturation of MP, leading to a dense aggregated network structure. The study suggested that Ab could be a promising ingredient in improving chicken MP's gel properties and developing fat-reduced meat products.     

Emulsion-forming properties of heat-induced pork myofibrillar protein affected by NaCl

The emulsification characteristics of myofibrillar proteins (MPs) with different NaCl concentrations also affect the quality of meat products after cooking. We investigated the effects of heating (100 °C) on the solubility, emulsifying activity, and conformational and environmental changes of MPs prepared with different NaCl concentrations. Emulsifying activity increased with increasing NaCl prior to heating, but there was no significant effect after heating. The viscosity increased and particle size decreased with increasing NaCl before heating, but these properties did not change after heating. NaCl did not affect the amount of α-helix and β-sheet. We deduced that the different emulsifying activity of myofibrillar proteins with different NaCl concentrations after heating may have been due to changes in the local environment of MPs. An understanding of the physicochemical and functional properties of MPs would unlock an area for development of meat products at different NaCl and temperature in the food industry.     

Quality changes and storage life of common carp (Cyprinus carpio) at various storage temperatures

The shelf life and freshness changes in pond-grown common carp (Cyprinus carpio L) during storage at 0–2°C, 5–6°C and room temperature (26–29°C) were investigated by sensory, microbiological, physical and chemical analyses. The effect of gutting on the shelf life during storage at 0–2°C was examined. Iodine/starch and potassium sorbate were examined for their effects on shelf life of whole fish stored at 0–2°C and 5–6°C. Sensory results indicated that the whole fish had a maximum shelf life of 24 to 25 days at 0– 2°C. The life of the fish to the point beyond which it would be unsuitable for sale (commercial shelf life) was 17 days at 0–2°C. Storage at 5–6°C shortened shelf life 2- to 2.5-fold. At room temperature (26–29°C), spoilage was evident after 13 h. Gutting the carp shortened its storage potential at 0–2°C. Iodine treatment of this species stored at 0–2°C and at 5–6°C did not extend shelf life. The maximum shelf life of sorbate-treated fish at 0–2°C and 5–6°C was extended by 1–2 days, commercial shelf life by 3–4 days. Total volatile basic nitrogen, pH and penetrometer analyses were not reliable indicators of changes in freshness during shelf life. Thiobarbituric acid values were not useful as rancid odours or flavours were not detected during storage.     

食用胶对猪肉肌原纤维蛋白功能特性的影响

将不同添加量的卡拉胶、亚麻籽胶、黄原胶和魔芋胶添加到猪肉肌原纤维蛋白溶液中,通过测定肌原纤维蛋白的乳化能力、凝胶质构特性、保水性和凝胶白度,研究食用胶对肌原纤维蛋白功能特性的影响。结果表明:与未添加食用胶的对照组相比,四种食用胶均可显著提高肌原纤维蛋白的乳化能力、凝胶硬度和弹性以及保水性(p<0.05),且添加量越高,增加的幅度越大;但添加食用胶后,肌原纤维蛋白的凝胶白度略有下降。因此,卡拉胶、亚麻籽胶、黄原胶和魔芋胶对肌原纤维蛋白的功能特性具有显著的影响。      

Modification of myofibrillar protein functional properties prepared by various strategies: A comprehensive review

Today, both consumers and food industry producers have exhibited an ever-growing interest in improving and broadening the functional performance of proteins in food industry. Myofibrillar protein (MP) is mainly responsible for texture, yield and organoleptic characteristics of final meat products. To increase functional properties of MP, technological and nutritional improvement of MP is needed to modify its structure and functionalities. Considerable approaches, including additives, oxidation treatments, and novel food processing technologies, have been utilized to modify its functional properties to manufacture acceptable meat products with lower cost and more desirable nutritional characteristics. However, a comprehensive summary of structural and functional changes of MP in response to different modification strategies is still lacking. Hence, in this review paper, our main goal is first to provide an overview of the functional characteristics of MP. Then, this review will mainly discuss the current knowledge on the functional changes of MP caused by various modification methods and will present some examples of previous works and recent progress. Finally, future outlooks are presented to tailor the manufacture of functionality enhanced and value-added muscle-based products and enable modified MP can be applied as a novel meat ingredient in food industry.     

Changes in myofibrillar structure of silver carp (Hypophthalmichthys molitrix) as affected by endogenous proteolysis under acidic condition

Effect of endogenous proteolysis on myofibrillar conformational changes under acidic condition was investigated by spectroscopic techniques. The result of intrinsic tryptophan fluorescence showed that tryptophan residues were exposed to polar environment by acid denaturation of protein and participation of endogenous proteolysis. Extrinsic fluorescence indicated that average surface hydrophobicity (S_hANS) decreased by reduction of pH but increased by endogenous proteolysis. Second‐derivative UV‐spectroscopy implied that the decrease of S_hANS under acidic condition may be due to burying of some aromatic amino acid residues into hydrophobic cores induced by acid‐induced aggregation, such as tyrosine, while S_hANS increased by exposure of some hydrophobic amino acids due to the effect of endogenous proteases. Raman spectra verified the changes in microenvironment of tryptophan and tyrosine residues, and showed that aliphatic amino acids were mainly exposed to polar solvent by both acid denaturation and endogenous proteolysis. In addition, new disulphide bonds were less likely to form by acid‐induced aggregation and proteolytic cleavage, while random coils increased and smaller water domains were found.     

Structures and properties of chicken myofibrillar protein gel induced by microwave heating

Structures and properties of myofibrillar protein gel prepared at different power (300–800 W) were evaluated. Amino acid analysis demonstrated that changes in microwave power did not alter primary structure of gel. However, an increase in microwave power could change higher structures of gel. As microwave power increased, α-helix content decreased and β-sheet content increased. Increased microwave power probably facilitated protein to unfold and expose the internal groups, causing surface hydrophobicity and the formation of disulphide bonds were enhanced, which indicated changes in tertiary and quaternary structures of protein. At 500 W, gel had the best ultrastructure where surface morphology, springiness and water holding capacity reached the optimum. Our findings suggested that microwave at an appropriate power (500 W) could change higher structures of myofibrillar protein gel to achieve desired processing and quality protein gel characteristics.     

白酒对秋刀鱼肌原纤维蛋白结构和功能性质的影响

以秋刀鱼为原料,研究白酒添加量对秋刀鱼肌原纤维蛋白(Myofibrillar protein,MP)溶解度、乳化性、浊度、表面疏水性、凝胶特性和巯基含量的影响。结果表明:随着白酒添加量的增加,MP溶解度、乳化性、凝胶硬度、弹性、咀嚼性、内聚性及保水性呈先上升后下降的趋势,凝胶白度值无明显变化;浊度、表面疏水性、巯基含量呈先下降后上升的趋势。整体来看,白酒处理对秋刀鱼肌原纤维蛋白的功能特性影响较大,且在白酒添加量为5%~7%时对凝胶特性的改善效果较好。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳研究发现,白酒能够促进蛋白质的溶解,并使溶出的蛋白质通过聚合作用形成大分子物质。     

液氮冻结对养殖大黄鱼肌原纤维蛋白结构的影响

目的 探究液氮冻结对大黄鱼肌原纤维蛋白结构的影响。方法 通过荧光分光光度法、傅里叶红外法、圆二色光谱法、激光拉曼光谱法等分析, 探究液氮冻结对大黄鱼肉肌原纤维蛋白结构的变化。结果 冻结后大黄鱼肉肌原纤维蛋白表面疏水性上升, 巯基含量下降, 蛋白质二、三级结构在冻结下发生改变, α-螺旋的含量被下降, 转化为β-折叠和无规卷曲, 影响肽链结合的紧密性。结论 蛋白结构的变化影响大黄鱼肉中肌原纤维蛋白的二、三级结构, 进而影响鱼肉的品质特性。     

Gel properties of surimi from silver carp (Hypophthalmichthys molitrix) as affected by heat treatment and soy protein isolate

The effects of setting conditions and soy protein isolate (SPI) on textural properties of surimi produced from silver carp were investigated. Effects of setting temperature, setting time and protein concentration on the gel strength were evaluated and compared utilizing response surface methodology. Models for breaking force and breaking distance of silver carp surimi were established. The total protein content was 13.4% in all experimental samples. Setting temperature and protein concentration were the major factors affecting the gel strength. In the range of the additive SPI protein (10–40%), breaking force and distance of silver carp surimi gels decreased when the protein ratio of SPI was increased in the total protein at 30 and 40 °C for 60 min setting and heating at 85 °C for 30 min, but the breaking force obtained for 90% surimi protein plus 10% SPI protein was higher than surimi alone at 50 °C for 60 min incubation and heating at 85 °C for 30 min.