低温等离子体对南美白对虾肌肉蛋白质性质和结构的影响

目的 研究低温等离子体（cold atmospheric plasma, CAP）对南美白对虾肌肉蛋白质性质和结构的影响。方法 采取不同等离子体条件（电压：20、40、60 kV;时间：1、2、3 min）对南美白对虾肌肉蛋白进行处理,通过分析肌浆蛋白、肌原纤维蛋白、表面疏水性、总巯基含量、Ca2+-ATPase活性、十二烷基硫酸钠-聚丙烯酰胺电泳(sodium dodecyl sulfate polyacrylamide gel electrophoresis, SDS-PAGE)指标,探讨了CAP对南美白对虾肌肉蛋白的影响。结果 与对照组相比,随着处理时间和电压的增加,虾体的肌浆蛋白、肌原纤维蛋白含量、总巯基含量、Ca2+-ATPase活性均显著下降（P<0.05）,而表面疏水性显著升高（P<0.05）。处理条件为60 kV、3 min时,样品各指标变化最明显。SDS-PAGE电泳显示肌原纤维蛋白的肌球蛋白重链条带增强,副肌球蛋白条带逐渐消失,在分子量为25 kDa附近出现新的蛋白条带。结论 CAP处理能导致南美白对虾肌肉氧化,蛋白质变性。     

鱼肉蛋白的热变性研究进展

为探究盐浓度对欧洲鳗肌原纤维蛋白热诱导凝胶形成性能的影响,测定了蛋白的浊度、表面疏水性和活性巯基的变化,考察了0.1、0.3、0.5 mol/L的NaCl浓度下的肌原纤维蛋白热诱导凝胶的性质。结果表明,欧洲鳗肌原纤维蛋白的浊度、表面疏水性和活性巯基分别在30、35和40 ℃开始增加。随着NaCl浓度的增加,肌原纤维蛋白的热吸收峰温度降低,而储能模量和损耗模量增加。0.5 mol/L NaCl溶解的欧洲鳗肌原纤维蛋白热诱导凝胶破断强度为98.81 g,高于低浓度NaCl溶解的蛋白热诱导凝胶。电泳结果表明,增加NaCl浓度会促进肌球蛋白重链和肌动蛋白的相互作用。根据傅里叶变换红外光谱和扫描电镜结果,发现0.5 mol/L NaCl溶解的肌原纤维蛋白热诱导凝胶具有最高的酰胺II/酰胺I强度比和最致密的网络结构。研究结果表明欧洲鳗肌原纤维蛋白在35 ℃时开始变性,提高NaCl浓度可以增强热诱导蛋白凝胶的强度和网络结构致密度,将为利用盐浓度和温度调控鳗鱼加热调理产品提供理论指导。     

Biochemical characterisation of Alaska pollock,Pacific whiting,and threadfin bream surimi as affected by comminution conditions

Salt-soluble protein, surface reactive sulfhydryl content, and surface hydrophobicity of Alaska pollock, Pacific whiting, and threadfin bream surimi were characterised, as affected by various comminution conditions. Chopping time/temperatures were explored in consideration of their habitat temperatures. Salt-soluble protein (SSP) significantly decreased when chopping time was extended. Corresponding to our follow-up study, no relationship between SSP and gel texture was found. Surface hydrophobicity was inversely proportional to SSP concentration, indicating the unfolding of protein upon comminution. Alaska pollock surimi demonstrated aggregation during chopping at 10 and 20 °C, based on the surface hydrophobicity. Surface reactive sulfhydryl (SRSH) contents of the three fish species behaved differently. The SH groups were oxidized to disulphide bonds when higher chopping temperature was applied. As a result, increased SRSH content was not observed in Alaska pollock (10 and 20 °C chopping) and threadfin bream paste (25 and 30 °C chopping).     

热处理温度及时间对镜鲤鱼肌原纤维蛋白热聚集行为的影响

通过测定蛋白溶解度、浊度、表面疏水性、巯基含量、破碎力等指标并结合傅里叶变换红外光谱分析,探究热处理温度(30～90℃)和保温时间(0～60min)对镜鲤鱼肌原纤维蛋白热聚集行为的影响.结果表明,镜鲤鱼肌原纤维蛋白热诱导聚集具有高度的温度依赖性.30℃处理条件下,蛋白变性程度较小,活性巯基含量增加,总巯基含量不变,二硫...     

儿茶素对肌原纤维蛋白氧化、结构及凝胶特性的影响

采用羟自由基氧化体系（10 μmol/L FeCl3、100 μmol/L VC和1 mmol/L H2O2）研究不同添加量儿茶素（10、50、100、150 μmol/g）对肌原纤维蛋白氧化、结构及凝胶特性的影响,同时以未氧化和氧化后未添加儿茶素（0 μmol/g）肌原纤维蛋白作为对照组,对肌原纤维蛋白羰基含量、总巯基含量、表面疏水性、溶解度、粒径分布、凝胶强度、凝胶保水性及肌原纤维蛋白流变特性进行测定,并观察凝胶微观结构。结果表明：添加儿茶素能减少羰基化合物的产生,但添加量过高会促进肌原纤维蛋白氧化;与未氧化和未添加儿茶素组相比,添加儿茶素降低了肌原纤维蛋白表面疏水性;随着儿茶素添加量增加,肌原纤维蛋白巯基含量逐渐降低,溶解度显著降低,粒径逐渐增大,凝胶强度和保水性逐渐下降,凝胶微观结构更加疏松多孔,蛋白胶束聚集,中、高添加量（50、100、150 μmol/g）儿茶素使得肌原纤维蛋白失去典型的流变曲线。中、高添加量儿茶素与肌原纤维蛋白发生共价交联,并导致肌原纤维蛋白发生疏水性聚集,最终削弱了肌原纤维蛋白的凝胶特性。     

Improvement of pea protein gelation at reduced temperature by atmospheric cold plasma and the gelling mechanism study

Pea protein as an alternative of soy protein has attracted growing interest in food industries. However, high temperature (> 95 °C) is required to enable heat-induced gelation and the formed gels are relatively weak. This research aimed to study the efficacy of atmospheric cold plasma (ACP) as a novel non-thermal technique to improve the gelling properties of pea protein. While native pea protein concentrate (PPC) (12 wt%) could not form gel under 90 °C, ACP-treated PPC showed good gelling properties when heated at 70–90 °C. The gels exhibited homogeneous three-dimensional network structure with interconnected macropores, and those prepared at 80 and 90 °C possessed good mechanical strength and viscoelasticity, as well as high water holding capacity. The gelling mechanism was studied by monitoring pea protein structural changes during ACP treatment and gel formation process via a transmission electron microscope, a Fourier transform infrared spectrometer, and a rheometer. These results revealed that ACP treatment contributed to the formation of protein fibrillar aggregates, and significantly reduced the PPC denaturation temperature, leading to protein unfolding at reduced temperature of 80–90 °C. ACP treatment also increased the protein surface hydrophobicity and exposed free sulfhydryl groups, which could facilitate the formation of hydrophobic interactions and disulfide bonds, leading to gels with improved mechanical properties. Moreover, hydrogen bonding could play an important role to stabilize the gel network during the gelling process. Owing to the short exposure time and energy efficiency, ACP is a promising technology to enable wide applications to pea protein as a gelling ingredient of plant protein-based food products, such as meat analogues and egg alternatives.     

低温等离子体处理加速罗非鱼肌原纤维蛋白的氧化及结构改变

以新鲜罗非鱼为研究对象,采用不同时间（0、1、2、3、4、5 min）和电压（40、50、60、70、80 kV)进行处理,分析处理后鱼肉的羰基含量、巯基含量、疏水性、Zeta电位、SDS-PAGE凝胶电泳、紫外光谱、荧光光谱和拉曼光谱,探究低温等离子体处理对罗非鱼肌原纤维蛋白氧化及结构的影响。结果表明:随着低温等离子体处理时间延长及电压升高,鱼肉中羰基含量和疏水性逐渐增加,总巯基和活性巯基含量减少;当处理时间延长至5 min时,总巯基和活性巯基分别减少至66.91 和52.76 μmol/g;处理电压升高至80 kV时,羰基含量从1.23 nmol/mg上升至2.16 nmol/mg;处理低温等离子体处理使肌原纤维蛋白Zeta电位绝对值降低;SDS-PAGE表明,低温等离子体处理使肌原纤维蛋白的肌球蛋白重链条带加重;随着低温等离子体处理时间的延长及电压的升高,紫外吸收光谱蓝移并且吸收强度增强,荧光吸收强度减弱;鱼肉经高电压、长时间等离子体处理后,α-螺旋增加,β-转角和β-折叠减少,无规卷曲无明显变化。综上,低温等离子体处理能够加速肌原纤维蛋白氧化,导致蛋白质的二级结构和构象发生改变。     

Effects of direct current magnetic field treatment time on the properties of pork myofibrillar protein

This study investigated the effects of direct current magnetic field (DC-MF) treatment time (1, 3, 5, 8 h) on properties of porcine myofibrillar protein (MP). Gel water-holding capacity increased from 83.40% to 87.20% when DC-MF-treatment time changed from 1-h to 8-h. The 3-h treatment time of DC-MF was found to promote MP unfolding, rearrangement and aggregation, leading to the loss of total sulfhydryl, the increase of reactive sulfhydryl, surface hydrophobicity, turbidity as well as the formation of MP clusters and the greater degree of crosslinking as compared with 0-h treatment, thus a firmer and more ordered MP gel network for trapping more water. However, excessive DC-MF treatment (8-h) weakened DC-MF effect on MP aggregation as well as gel network and texture. This study has shed light on the effects of DC-MF treatment time on MP properties and provides useful information for the application of DC-MF in the food industry.     

羟自由基氧化对牛肌原纤维蛋白结构与乳化性能的影响

采用Fenton氧化体系构建羟自由基模拟氧化体系,探究不同氧化强度下牛肌原纤维蛋白结构与乳化性能的变化及其内在联系.结果表明:随H2O2浓度(0、0.5、1、5、10、20?mmol/L)的增加,肌原纤维蛋白的氧化程度加剧,羰基含量、二聚酪氨酸和表面疏水性逐渐增加,总巯基和游离巯基含量逐渐下降;α-螺旋相对含量呈下降趋...     

Physicochemical Changes in Alaska Pollock Surimi and Surimi Gel as Affected by Electron Beam

ABSTRACT: Alaska pollock surimi and surimi gels (cooked) were subjected to various doses of electron beam (e-beam). Shear stress of surimi gels increased as the dose increased up to 6 to 8 kGy and then decreased. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed gradual degradation of myosin heavy chain as the dose increased. The degradation was slower for frozen samples. The integrity of actin was slightly affected by high doses (25 kGy). The amount of sulfhydryl groups and the level of surface hydrophobicity of Alaska pollock surimi decreased as the dose increased, suggesting formation of disulfide bonds and hydrophobic interactions. The sulfhydryl groups and hydrophobicity of surimi gels increased as the dose increased up to 6 kGy and then decreased.     

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%.     

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.     

Dynamic rheology and thermal transitions of surimi seafood enhanced with ω-3-rich oils

Surimi-based seafood products are widely accepted and enjoyed worldwide. The U.S. consumption increased in 1980s; however, it leveled thereafter. Food products nutrified with ω-3 polyunsaturated fatty acids (PUFAs) are in increasing demand due to demonstrated health benefits. Currently, surimi seafood is not nutrified with ω-3 PUFAs. In the present study, surimi seafood was nutritionally-enhanced with ω-3 PUFAs-rich oils (flaxseed, algae, menhaden, krill, and blend). Protein endothermal transitions, heat-induced gelation (elastic modulus, G′), and fundamental texture properties (shear stress) of Alaska pollock surimi nutrified with ω-3 PUFAs-rich oils (flaxseed, algae, menhaden, krill, and blend) were determined and compared to Alaska pollock surimi without oil (control). Differential scanning calorimetry showed that oil addition enhanced thermal transition of actin and did not compromise the transition of myosin. The addition of oil improved heat-induced protein gelation as demonstrated with dynamic rheology. Elastic modulus increased when oil was added. There were no differences (P > 0.05) in shear stress between surimi gels with and without oil, indicating that nutrification with ω-3 PUFAs-rich oils within the ranges tested did not alter gel strength. This study demonstrates that the nutritional value and gelation of surimi seafood can be enhanced without altering texture properties by addition of ω-3 PUFAs-rich oils.     

食盐腌制对鸡肉品质、肌原纤维蛋白结构和功能特性的影响

为探究食盐浓度对冷藏腌制过程中鸡肉品质和肌原纤维蛋白的影响,将鸡肉置于不同浓度（0%、1.6%、3.2%、4.8%、6.4%、8.0%）的食盐腌制液中,进行不同时间（0.2、1、2、3、4 d）的冷藏腌制后,测定鸡肉的水分含量、持水性以及肌原纤维蛋白的溶解度、表面疏水性、羰基、巯基、二聚酪氨酸含量等。结果表明：经过不同浓度食盐液的腌制,鸡肉的持水性和肌原纤维蛋白表面疏水性发生变化,随着腌制时间的延长羰基含量和二聚酪氨酸含量增大,肌原纤维蛋白的溶解度、热稳定性、巯基含量降低,部分α-螺旋转化为β-折叠。随着食盐液浓度增大羰基和二聚酪氨酸含量先增加后减小,巯基含量不断增大,并且食盐液浓度范围为3.2%～4.8%时肌原纤维蛋白各特性指标变化较大。综上,食盐腌制能促使鸡肉肌原纤维蛋白结构和功能发生改变,此研究结果可为控制腌制过程中鸡肉品质变化和其肌原纤维蛋白氧化提供理论依据。     

芦丁诱导猪肉肌原纤维蛋白结构变化对蛋白凝胶特性的改善作用

向猪肉肌原纤维蛋白氧化体系(40 mg/mL蛋白、10 μmol/L FeCl3、100 μmol/L VC和1mmol/L H2O2)中添加不同量的芦丁(0、10、50、100、150 μmol/g,以蛋白计),测定蛋白质的巯基含量、表面疏水性、电泳、溶解度、凝胶强度和保水性、流变特性,研究芦丁对肌原纤维蛋白结构和凝...     

Effects of hydroxyl radical induced oxidation on water holding capacity and protein structure of jumbo squid (Dosidicus gigas) mantle

Protein oxidation is considered as an important issue in food preservation process. In the present study, the potential influence of protein oxidation on water holding capacity and protein structure of jumbo squid (Dosidicus gigas) mantle was investigated. After the hydroxyl radical oxidation, it was found that the carbonyl, surface hydrophobicity and dityrosine content of myofibrillar protein significantly increased (P < 0.05), while the content of total sulphydryl decreased significantly (P < 0.01). Meanwhile, the fluorescence intensity of squid was weakened, and the maximum absorption peak of fluorescence red shift as the H₂O₂ concentration increased. The sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed that not only the protein cross-linking but also degradation could have occurred. The content of α-helix decreased, the content of β-sheet, β-turn and the unordered structures increased after oxidation. In addition, oxidation resulted in a decrease in water holding capacity. Taken together, oxidation resulted in the damage of the myofibrillar structure, the increase in muscle loss rate and the decrease in water holding capacity.     

Modification of functional,rheological and structural characteristics of myofibrillar proteins by high-intensity ultrasonic and papain treatment

The effects of sonication duration (15 and 30 min) and papain enzyme treatments on the conformational, physicochemical and functional traits of myofibrillar proteins (MPs) were addressed in this study. As the ultrasound duration was increased, the water holding capacity (WHC), solubility, foaming and emulsifying properties were improved as a result of the changes in the particles size distribution and zeta potential. Our results indicated that the turbulence force caused increments in the surface hydrophobicity and significant changes in the secondary structure. Also, the rheological properties were influenced by both cavitation force and papain treatment. According to the observations, the samples treated with sonication (for 15 and 30 min) and enzyme were more elastic with higher viscosity, as compared to the control. Compared with the control, enzymolyzed samples indicated better functionality. Moreover, papain treatment led to the increase of the hydrophobicity groups on the surface of proteins and the decrease of the amount of α-helix and β-sheet structures. It was noteworthy that the most changes in the structure and techno-functionality of myofibrillar proteins were observed for the sample affected by the simultaneous application of papain treatment and 15 min sonication. The highest values in the surface hydrophobicity, specific surface area, net charge, storage modulus, solubility and WHC belonged to this sample. However, enzyme-modified samples exposed to the longer sonication time (30 min) demonstrated reductions in solubility, WHC and surface hydrophobicity, as well as increases in the particle size distribution and protein turbidity.     

Improved gelation functionalities of myofibrillar protein from pale,soft and exudative chicken breast meat by nonenzymatic glycation with glucosamine

The potential of nonenzymatic glycation of myofibrillar proteins (MPs) to improve the gelation functionalities of pale, soft and exudative (PSE‐like) chicken breast meat was investigated. MP suspensions (4 mg mL^?1) obtained from both normal and PSE‐like chicken breast meat were mixed with glucosamine at a ratio of 1:6 (protein : glucosamine) in phosphate‐buffered saline (0.6 m KCl, 20 mm K₂HPO₄/KH₂PO₄, 0.02% NaN₃ and pH 7.5) and incubated at 37 °C for 12 h. Untreated normal and PSE‐like MP suspensions maintained at 4 °C were used as positive and negative controls, respectively. The glycation treatment increased the surface hydrophobicity but decreased the reactive sulfhydryl contents compared to those of the control (P < 0.05), indicating that the tertiary conformation of the protein changed. Correspondingly, these glycated samples also exhibited significant improvements in gel strength and the water‐holding capacity (P < 0.05). Conclusively, nonenzymatic glycation is a potential technique to improve the properties and offer a means for effective use of PSE‐like meat.     

超高压辅助脱壳对虾夷扇贝肌原纤维蛋白生化特性及结构的影响

本实验采用150～350 MPa保压3 min处理虾夷扇贝,以手工脱壳和蒸煮脱壳为对照,首先通过测定脱壳时间以及得肉率考察压力对脱壳效果的影响,再通过测定肌原纤维蛋白的质量浓度、总巯基含量、羰基含量、表面疏水性、Ca2＋-ATPase活力及分析其二级结构单元的变化规律,研究超高压处理对虾夷扇贝贝肉肌原纤维蛋白生化特性及结构的影响。结果表明：在250 MPa条件下保压3 min能提高扇贝的脱壳效果;超高压处理导致虾夷扇贝肌原纤维蛋白发生一定程度的变化,总体表现为表面疏水性和羰基含量增加,总巯基含量、Ca2＋-ATPase活力降低;肌原纤维蛋白α-螺旋和β-转角相对含量降低,β-折叠和无规卷曲相对含量升高;超高压对扇贝贝肉肌原纤维蛋白的影响相对较小,有利于维持其蛋白生化特性,保持扇贝贝肉食用品质和加工性能。研究结果可为贝类在超高压处理过程中肌原纤维蛋白品质的控制提供一定的参考。     

转谷氨酰胺酶对鲤鱼肌原纤维蛋白乳化活性和凝胶特性的影响

目的:研究添加转谷氨酰胺酶(Transglutaminase,TG)对鲤鱼肌原纤维蛋白乳化活性和凝胶特性的影响,为改善鱼糜制品的品质特性提供理论依据。方法:肌原纤维蛋白溶液浓度为40 mg/mL,TG添加量为蛋白溶液的0%、0.1%、0.2%、0.3%、0.4%(W/V),测定蛋白溶液的乳化活性及凝胶特性指标。结果:随着TG添加量的增加肌原纤维蛋白溶液乳化活性降低(p<0.05);TG添加增大了蛋白浊度(p<0.05);蛋白流变结果表明,随着TG添加量的增加显著增大储能模量(G')(p<0.05),降低起始凝胶温度,并提高蛋白变性温度;与对照相比,添加0.1%的TG会降低凝胶持水性,但是进一步增加TG对凝胶持水性影响不显著(p>0.05);添加TG显著降低了凝胶白度(p<0.05);凝胶质构测定结果显示,随着TG添加量的增加,会改进蛋白质的凝胶特性,显著增加凝胶弹性和硬度(p<0.05)。结论:肌原纤维蛋白中添加TG到能够降低蛋白的乳化特性,但会改进肌原纤维蛋白的凝胶特性。