The effect of myofibrillar/sarcoplasmic protein ratios on the properties of round scad muscle protein based film

The effect of the ratios of myofibrillar protein (MP) to sarcoplasmic protein (SP) from round scad (Decapterus maruadsi) muscle on the properties of the resulting films was investigated. Tensile strength (TS) of films decreased with increasing SP content (p < 0.05). Films prepared from MP/SP ratio of 10:0 (w/w) exhibited the highest TS (p < 0.05). Elongation at break (EAB) of films prepared with SP content greater than 30% had the decreased EAB (p < 0.05). Water vapor permeability (WVP) of films increased when SP content increased up to 20% and decreased with increasing SP content up to 30% (p < 0.05). Solubility of films decreased but protein solubility increased with increasing SP contents (p < 0.05). The a*-value and ΔE* of film increased with increasing SP content. Films with all MP/SP ratios exhibited the negligible transmission to the light in UV range. Therefore, it is suggested that the type and ratio of proteins in fish muscle, both SP and MP, influenced the properties of film from round scad muscle. Results suggested that the removal of sarcoplasmic protein from fish muscle by thorough washing was an effective means to improve the mechanical properties as well as color of the fish muscle protein-based film.     

Effects of oxidative modification on gel properties of isolated porcine myofibrillar protein by peroxyl radicals

AAPH-derived (2,2′-azobis (2-amidinopropane) dihydrochloride) peroxyl radicals were selected as representative free radicals of lipid peroxidation to investigate the effects of oxidative modifications on isolated porcine myofibrillar protein structures as well as their rheological and gelling properties. Incubation of myofibrillar protein with increasing concentrations of AAPH resulted in a gradual increase (p < 0.05) in carbonyl content and SH → S–S conversion. Results from SDS-PAGE indicated that medium (~ 1 mM) and relatively high (> 3 mM) concentrations of AAPH induced aggregation of myosin and denaturation of myosin, troponin and tropomyosin, respectively. These structural changes resulted in changes on gelation of myofibrillar protein. Low level protein oxidation (AAPH ≤ 0.5 mM) had no remarkable effect (p > 0.05) on the viscoelastic pattern of myofibrillar protein gelation. Moderate oxidative modification (AAPH ~ 1 mM) enhanced the water-holding capacity (WHC) and texture properties of gels, while further oxidation (AAPH > 3 mM) significantly reduced the gel quality.     

Kinetics of phase separation during pressure-induced gelation of a whey protein isolate

The kinetic process of pressure-induced gelation of whey protein isolate (WPI) solutions (20–28%, w/v) was studied using in situ light scattering. The gelation of WPI solutions could be induced by pressurization at 250 MPa, a pressure lower than that reported in other studies. The gelation time decreased with increasing WPI concentration and followed an exponential rule. The relationship of the logarithm of scattered light intensity (I) versus time (t) was linear after the induced time and could be described by the Cahn–Hilliard linear theory. With increasing time, the scattered intensity deviated from the exponential relationship, and the time evolution of the scattered light intensity maximum I_m and the corresponding wavenumber q_m could be described in terms of the power-law relationship as I_m  t^β and q_m  t^−α, respectively. These results indicated that phase separation occurred during the gelation of WPI solutions under high pressure.     

The physico-chemical properties and protein denaturation potential of surfactant mixtures

Protein denaturation was investigated to establish an in vitro evaluation method of surfactants in connection with their in vivo irritation potency to human skin. Eventually a new method with simplicity and high reproducibility was established by using quantitative analysis with gel-permeation chromatography (GPC). The protein denaturing potency of the commercially available surfactants was measured by using the developed method. Synergistic reduction in protein denaturation was observed in the mixed systems of anionic and amphoteric surfactants. The synergistic reduction was explained in terms of the physico-chemical properties of the mixed surfactants. A possible mechanism is the remarkable lowering of the total monomer concentration by the formation of hydrophobic complexes between the anionic and amphoteric surfactants.
Relation entre les propriétés physico-chimiques des mélanges de surfactifs et leur potentiel de dénaturation des protéines     

The effect of protein profile and preheating on denaturation of whey proteins and development of viscosity in milk protein beverages during heat treatment

The effect of preheat temperature (63 or 77 °C for 30 s; final heat 120 °C for 30 s) and casein to whey protein ratio on the physical characteristics of 3.3%, w/w, dairy protein beverages was investigated. Dispersions preheated at 77 °C had lower viscosity than dispersions preheated at 63 °C. Casein‐containing dispersions had significantly lower levels of α‐lactalbumin denaturation than whey protein‐only dispersions. A higher proportion of casein improved the thermal stability of protein dispersions. Overall, alteration of preheat temperature and casein to whey protein ratio can influence dairy beverage quality, with increasing levels of casein reducing physical changes due to heat treatment.     

Decreased gelling and emulsifying properties of myofibrillar protein from repeatedly frozen-thawed porcine longissimus muscle are due to protein denaturation and susceptibility to aggregation

The effects of freeze–thaw cycles (FT, 0, 1, 3 and 5 times) on protein functional properties of porcine longissimus muscle were investigated. FT increased gapping between muscle fibres and tore muscle fiber bundles. Myofibrillar protein (MP) isolated from FT muscle showed an increased hydrophobicity (P < 0.05), reduced thermal transition temperatures (T_max) and enthalpy of denaturation (ΔH) (P < 0.05), and enhanced susceptibility to thermal aggregation. These structural changes resulted in major losses in protein functionalities, e.g., 41–43% reductions (P < 0.05) in MP emulsifying capacity and emulsion stability after five FT cycles. The ability of MP to form a viscoelastic gel network, as analyzed by small-strain oscillatory rheological testing, also attenuated with FT cycles. The FT process lowered (P < 0.05) water-holding capacity (WHC), whiteness, and texture (hardness, springiness, chewiness and cohesiveness) of MP gels. Overall, repeated FT had a detrimental effect on the general functionality of porcine MP, and protein denaturation and aggregation were implicated in the functionality losses.     

淡水鱼蛋白质冷冻变性的研究现状及前景

主要介绍了淡水鱼蛋白质冷冻变性的国内外研究现状,探讨了防止淡水鱼蛋白质冷冻变性的常用技术,并综述了淡水鱼蛋白质抗冷冻变性的研究方法和发展前景。      

微波能强度与鸡胸肉中蛋白质变性的关系

本文以鸡胸肉为研究对象,探讨微波能强度与鸡肉中肌浆蛋白和肌原纤维蛋白变性的关系。分别采用低火力、中火力、高火力,加热鸡胸肉30、60、90、120s,采用双缩脲法和SDS-PAGE电泳分析肌浆蛋白和肌原纤维蛋白的变化情况。结果表明:肌浆蛋白提取液浓度随着加热火力和时间的增加浓度迅速降低,肌原纤维蛋白提取液浓度在低火力和中火力加热条件下先上升后下降,高火力条件下则一直降低;肌原纤维蛋白的热稳定性高于肌浆蛋白,30～40ku之间的蛋白热稳定性较高,在高火力加热到90s以后才完全变性沉淀。     

鱼肉蛋白的热变性研究进展

在鱼肉蛋白的加工过程中,加热处理是最常见的工序之一。热处理造成的蛋白热变性会对蛋白质的理化性质和功能特性产生很大的影响,且这种影响多难以复原。本文总结了近几年来国内外关于鱼肉蛋白在加热过程中蛋白组成成分、总巯基和羰基、溶解度、浊度、黏度、Ca²⁺-ATPase活性、凝胶、质构等特性指标的变化趋势的研究进展,结合蛋白质热变性的机理深入分析其变化原因,提出今后在鱼类加工方面对于鱼肉蛋白热变性的研发方向,旨在为鱼制品选择合理的热加工工艺的提供理论依据。     

热变性对蛋白质理化性质的影响

本文论述了热变性对蛋白质结构、功能性质以及酶解性质的影响，揭示了蛋白质热变性后理化性质的变化是其二级、三级或四级结构改变的结果，并讨论了其它因素对热变性的影响。     

鱼肉蛋白质冷冻变性研究进展

主要综述了鱼肉蛋白质冷冻变性研究现状,介绍已取得的相关研究成果,比较防止鱼肉蛋白质冷冻变性的方法和手段。并对进一步研究鱼类及其他水产品蛋白质冷冻变性研究进行了讨论。     

Gelation properties of chicken myofibrillar protein induced by transglutaminase crosslinking

Gelation properties of chicken myofibrillar protein isolate (MPI) and the effect of microbial transglutaminase (MTG) were studied using a dynamic oscillatory rheometer and a texture analyzer. Final heating temperature had a great impact on gel stiffness and the maximum gel stiffness was obtained at 95 °C. pH and ionic strength also influenced gel stiffness and the maximum gel stiffness was achieved at pH 6, 0.9 M NaCl; however, less stiff gels were formed in 0.6 and 1.2 M NaCl. In the MPI concentration range of ∼0.5-5%, a positive correlation was observed between gel stiffness or gel peak force and MPI concentration. When MTG was included at levels of ∼0 to 12-15 U, positive linear relations were found between gel stiffness or peak force and MTG levels. However, negative correlations for these parameters were observed at higher MTG concentrations. When MTG level was greater than 15 U, gel stiffness or peak force tended to decrease. The improvement in gel strength or gel peak force for the MPI with inclusion of MTG suggested that some ε (γ-glutamyl) lysine (G-L) crosslinking occurred among myofibrillar molecules. Thus, MTG is useful in improving gelation properties of heat-induced MPI gel and provides new opportunities to expand the utilization of low value meat in muscle foods.     

High pressure induced changes in beef muscle proteome: Correlation with quality parameters

The relationship between pressure induced changes on individual proteins and selected quality parameters in bovine longissimus thoracis et lumborum (LTL) muscle was studied. Pressures ranging from 200 to 600 MPa at 20 °C were used. High pressure processing (HPP) at pressures above 200 MPa induced strong modifications of protein solubility, meat colour and water holding capacity (WHC). The protein profiles of non-treated and pressure treated meat were observed using two dimensional electrophoresis. Proteins showing significant differences in abundance among treatments were identified by mass spectrometry. Pressure levels above 200 MPa strongly modified bovine LTL proteome with main effects being insolubilisation of sarcoplasmic proteins and solubilisation of myofibrillar proteins. Sarcoplasmic proteins were more susceptible to HPP effects than myofibrillar. Individual protein changes were significantly correlated with protein solubility, L*, b* and WHC, providing further insights into the mechanistic processes underlying HPP influence on quality and providing the basis for the future development of protein markers to assess the quality of processed meats.     

预处理对干燥罗非鱼片蛋白质变性的影响及优化

以Ca2+-ATPase活性为指标,采用响应面优化分析,研究了预处理试剂丙二醇、丙三醇和NaCl的添加量对干燥罗非鱼片蛋白质变性的影响,得到较优预处理配方为丙二醇2%+丙三醇3%+NaCl1%。采用优化后的预处理配方对罗非鱼片进行预处理,分析干燥罗非鱼片蛋白质变性和组织结构的变化情况,结果表明,经过预处理的干燥罗非鱼片Ca2+-ATPase活性和盐溶性蛋白溶解度有了明显提高,干制样品的组织结构得到明显的改善,并且干燥温度对干燥罗非鱼片的蛋白质变性有显著影响,温度越高,变性程度越严重,组织结构破坏也越严重。      

蛋白溶解性分析法研究大米焙炒过程中蛋白质热变性行为

考察了焙炒过程中大米蛋白质的热变性行为,通过大米蛋白在不同功能溶剂中的溶解度变化了解大米蛋白质在焙炒过程中次级结构的变化及热变性信息。发现热变性主要发生在焙炒的前期,热变性包括蛋白质次级结构的变化和更高能级的化学变化。与传统蒸煮方法相比,焙炒大米的蛋白质热变性程度较低。粳米和糯米中的蛋白质热变性行为基本相似,选用不同的加热介质对大米蛋白的热变性没有影响。      

Gelling properties of myofibrillar protein from abalone (Haliotis Discus Hannai Ino) muscle

Texture of muscle food is dependent on the gelation properties of myofibrillar protein. Defining the performance of myofibrillar protein during gelation is beneficial for maintaining quality and developing muscle food. The myofibrillar protein from abalone muscle (AMP) was extracted and the gel-forming ability was investigated. The lowest protein solubility of AMP in distilled water was obtained at pH 5.5, but shifted to a lower pH value by ionic strength. The breaking force and deformation of AMP gel formed at pH 7.0 were 48.00 g and 27.70 mm, respectively, but they could not be detected at pH 5.0 and pH 5.5 due to the low gel-forming ability. Scanning electron microscopy data showed that a coarse and disorder gel containing clusters of agglomerates was observed at pH 5.0 and pH 5.5, but gradual compact network structure was observed in the gel formed at increasing pH. The glass transition temperature (Tg) of AMP gel formed at pH 5.5 was higher than that of AMP, and the Tg of AMP gel was increased with increasing the pH of gel-forming solution. It was found that the unfolding of tertiary structure of AMP at pH 7.0 was easier than that at pH 5.5 through the result of infrared spectra. We therefore conclude that both the solubility and gel-forming ability of AMP are pH dependent.     

Hydrolyzed wheat gluten suppresses transglutaminase-mediated gelation but improves emulsification of pork myofibrillar protein

The influence of 15-h chymotrypsin-hydrolyzed wheat gluten (GH) on microbial transglutaminase (MTGase)-mediated interaction, gelation and emulsification of pork myofibrillar protein isolate (MPI) was investigated at two ionic strengths (0 M and 0.6 M NaCl) and pH 6.5. MTGase treatments in 0 M NaCl solution decreased the size of myosin heavy chain through deamidation, but this was inhibited by GH or in 0.6 M NaCl where myosin polymerization dominated. Stabilization of MPI (thermal transitions) by the MTGase treatment was also diminished (P < 0.05) by the presence of GH at both ionic strengths. These GH-induced MPI physicochemical changes greatly weakened the ability of MTGase to promote MPI thermal gelation (gel storage modulus, P < 0.05), especially at 0.6 M NaCl, which was shown to result from reduced protein aggregation. However, GH improved (P < 0.05) emulsifying properties of MPI, regardless of MTGase treatment.     

丙二醛氧化修饰对大豆蛋白热变性影响

以丙二醛代表脂质过氧化活性次生产物,采用圆二色谱、内源荧光光谱、粒径分析和差示扫描量热仪研究丙二醛氧化修饰对大豆蛋白热变性影响。结果发现,丙二醛氧化修饰使大豆蛋白热稳定性下降,相比大豆球蛋白,大豆β-伴球蛋白热稳定性下降更为显著。     

SDS-PAGE方法鉴定鸡骨髓蛋白质热变性的研究

研究了不同的加热温度﹑加热时间对鸡骨髓中蛋白质变性程度的影响。结果发现,随着加热温度的升高加热时间的延长,电泳条带变少变浅,聚丙烯酰胺凝胶电泳可以作为检测鸡骨髓蛋白质变性程度,可应用于带骨鸡肉热熟程度的判定。     

Gelation properties of myofibrillar/pea protein mixtures induced by transglutaminase crosslinking

Gelation properties of mixtures of myofibrillar protein isolate (MPI)/pea protein isolate (PPI) were studied using a dynamic oscillatory rheometer and a texture analyzer to evaluate PPI as a possible meat product additive. The inclusion of microbial transglutaminase (MTG) increased the gel strength of MPI/PPI mixture (3% + 1%) more than it did for MPI (3%), but less than a 3% MPI, 1% soy protein isolate combination. The direct evidence of interaction between muscle and pea proteins in the form of new sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) bands was not found; however, the improvement in gel strength or gel peak force for the MPI/PPI mixture (3% + 1%) with inclusion of MTG suggested that some ? (γ-glutamyl) lysine (G-L) crosslinking occurred between muscle and pea proteins. It likely that pea protein acted as a non-gelling component and interspersed throughout the primary MPI gel network and the addition of MTG promoted partial crosslinking of MPI. Consequently, MTG is useful in improving gelation properties of heat-induced MPI/PPI gel.