Nutritional Properties and Metabolic Studies of Acylated Beef Heart Myofibrillar Proteins

Beef heart myofibrils were acylated with several concentrations of acetic (AA) and succinic (SA) anhydride, and digestibility and utilization of the myofibrillar proteins were determined. Results for in vitro hydrolysis of the untreated and acylated proteins varied, depending on the enzyme(s) used in the analysis. Rat protein efficiency ratios and net protein ratios for untreated (PER = 2.83, NPR = 116) and acetylked (PER = 2.55, NPR = 110) proteins were greater than for casein (PER = 2.50, NPR = 100), whereas values for succinylated proteins (PER = 2.36, NPR = 87) were less than for casein. Most of the radioactivity recovered after 24 hr from rats fed ¹⁴C-acylated myofibrillar proteins was in expired CO₂; 62.8% for ¹⁴C-acetylated and 45.8% for ¹⁴C-succinylated proteins. Rats acclimated to an acylated protein diet for 28 days showed improved metabolism of ¹⁴C-acetylated protein and decreased metabolism of ¹⁴C-succinylated proteins; 75.7% and 38.1% recovery as expired CO₂, respectively.     

Functional Properties of Myofibrillar Proteins from Cold-Shortened and Thaw-Rigor Bovine Muscles

Prerigor bovine sternomandibularis muscles were stored at 15, 0 and ?29°C to examine cold-shortening and thaw-rigor effects on myofibrillar protein extractability and gelation properties of myofibrils and salt-soluble protein (SSP). Frozen muscle that underwent severe contraction at thawing showed greater protein extractability (35%) than muscles stored at 0 and 15°C (27% extractability). Of the three tempered muscles, thaw-rigor muscle produced the strongest myofibril gel and cold-shortened muscle formed the most elastic SSP gel as determined by dynamic shear and penetration measurements. However, thermally induced changes in gel viscoelastic moduli for all protein samples followed similar patterns. Results indicated that physicochemical changes accompanying muscle contraction affected protein network formation during gelation.     

Functional Properties of Enzymatically Modified Beef Heart Protein

The effect of enzymatic modification on beef heart protein functionality was examined in model system and frankfurter experiments. Modification of heart myofibrils with ficin was effective in improving protein solubility and emulsification capacity compared to controls. Incorporation of enzyme-modified heart into a meat model system composed of 30% beef heart and 70% beef skeletal meat resulted in improved cooked yields which were equal to controls made with 100% skeletal meat, in both no-salt and 3% salt formulations. Normal (2%) and low (0.5%) salt frankfurters made with 30% enzyme-modified beef heart had significantly greater smokehouse yields and consumer cooked yields than frankfurters made with 30% unmodified heart.     

高温处理对牛肉蛋白质化学作用力及肌原纤维蛋白结构的影响

以牛背最长肌为研究对象,对其进行高温处理（110、115、121 ℃分别加热3、6、9、12、15 min）,通过分析蛋白质化学键、傅里叶变换红外光谱、紫外光谱、内源荧光光谱以及蛋白质片段大小等结构信息变化,探讨高温处理对牛肉蛋白质化学作用力及肌原纤维蛋白结构的影响。结果表明,随着处理温度的升高和加热时间的延长,牛肉蛋白中离子键和氢键含量显著下降（P＜0.05）,疏水相互作用和二硫键含量显著升高（P＜0.05）。肌原纤维蛋白二级结构发生重排,N—H和C—N伸缩振动以及N—H弯曲振动较为明显。高温处理促使芳香族氨基酸残基暴露于分子表面,并改变了肌原纤维蛋白质疏水区域的局部结构和蛋白质的三级结构。此外,在高温处理下肌原纤维蛋白发生了明显的降解聚集,并形成了大量小分子质量的蛋白片段。可见,高温处理能够显著改变牛肉蛋白质的化学作用力及肌原纤维蛋白的结构,本研究为高温处理下牛肉蛋白质变化机制的研究提供参考。     

Chemical Composition and Functional Properties of Acylated Low Phytate Rapeseed Protein Isolate

Protein isolates were prepared by isoelectric precipitation or dialysis of the first and second aqueous extracts of rapeseed flour which was unmodified or acylated by succinic or acetic anhydride. Acylation of the flour lowered the protein and phytic acid contents without significantly altering the amino acid composition of the isoelectrically precipitated protein isolates from the two extracts. The acylated protein isolates from the isoelectrically precipitated extracts had high nitrogen solubility, emulsifying and fat absorption properties. Isoelectrically precipitated and dialyzed acylated proteins did not differ in nitrogen solubility, but dialyzed unmodified protein isolates had nitrogen solubility which was considerably greater than that of isoelectrically precipitated proteins.     

Chemical and Functional Properties of Oxidatively Modified Beef Heart Surimi Stored at 2 °C

Beef heart surimi was prepared using 4 washing conditions: (1) sodium phosphate buffer alone, (2) buffer 1 NaCl, (3) buffer 1 propyl gallate, and (4) buffer 1 sodium tripolyphosphate. Surimi samples were stored at 2 8C and analyzed periodically for protein oxidation, emulsifying properties, and dynamic gelling characteristics. Degree of oxidation differed among washing treatments. Addition of propyl gallate and sodium tripolyphosphate inhibited lipid oxidation but did not prevent protein oxidation. Gel elasticity increased and emulsifying activity decreased for all surimi samples during storage, coinciding with myosin aggregation. Modification of beef heart surimi functionality can be achieved through different washing processes.     

复合肌原纤维蛋白的凝胶特性

温度是影响蛋白质凝胶特性的主要因素。实验通过研究复合肌原纤维蛋白凝胶(猪肉肌原纤维蛋白、鲢鱼肉肌原纤维蛋白质量比分别为2∶0、1∶1、0∶2)在70、80、90、100℃加热时色泽、凝胶强度、质构特性、水分分布的变化,对复合肌原纤维蛋白凝胶和单一肌原纤维蛋白凝胶之间凝胶特性的差异和相关性进行研究,优化蛋白凝胶加热温度。结果表明:1∶1复合的肌原纤维蛋白凝胶能结合单一蛋白凝胶的特点,改善肌原纤维蛋白的凝胶特性;低场核磁共振表明,温度可通过影响水分分布来影响蛋白质的凝胶特性;蛋白凝胶特性随温度升高而增强,但温度过高会出现劣化,90℃是较为理想的加热温度。     

Edible Packaging Films Based on Fish Myofibrillar Proteins: Formulation and Functional Properties

Biopackaging materials based on fish myofibrillar proteins have been developed. The effects of protein concentration, pH, temperature and storage time before casting on the apparent viscosity of the film forming solution (FFS) were evaluated using experimental design methodology. The first objective was to determine a feasible experimental range for film-forming. The pH and protein concentration had strong interactive effects on FFS viscosity. During FFS storage before casting, partial degradation of high molecular weight protein components led to decreased viscosity, allowing thin layer casting. In the experimental range for film-forming, none of the conditions affected film functional properties. Standard conditions were determined at: pH 3.0, 2.0g protein/100g FFS, 25°C and 6 hr storage. The functional properties of the standard biopackaging were slightly better than those that determined for known protein-based films, with tensile strength close to those of low density polyethylene films.     

Functional Properties of Acylated Oat Protein

Protein extracted from defatted oat (Avena sativa L., variety Sentinel) was acylated with acetic or succinic anhydride at levels of 0.05 and 0.20 g/g protein. Acetic anhydride was more reactive than succinic anhydride in modifying lysine groups. Total essential amino acid content was slightly lowered by acetylation but unaffected by succinylation. Gel filtration chromatography showed some dissociation of oat polypeptides by succinylation. Solubility, emulsifying properties and fat finding capacity were all markedly improved by acylation, and the effect was more pronounced with succinylation. Emulsifying capacity of meat was enhanced by blending with acylated oat protein. Water hydration capacity and foam stability were adversely affected by acylation. Results suggest that acylated oat protein may be a valuable functional ingredient in meat and other emulsion food products.     

Functional Properties of Acylated Pea Protein Isolates

Pea protein isolates were acylated with succinic and acetic anhydride at 1.0, 3.0, and 5.0 mmol anhydride/g protein. The chemically modified isolates showed increased emulsifying capacity, emulsion stability, foam capacity and stability, and water adsorption compared to untreated pea protein isolate. In general, the greater the extent of acylation, the greater the improvement in emulsification properties compared to the untreated protein isolate; however, improvement at greater than 3.0 mmol anhydride/g protein was slight. Acetylation at 3 mmol/g increased foam capacity to the greatest extent. Water adsorption was enhanced to the greatest extent in protein isolates acetylated at 5 mmol/g. Acylation lowered the isoelectric point of protein isolates compared to untreated isolate. In vitro enzyme hydrolysis of the protein isolates, as determined by a multienzyme system of trypsin, chymotrypsin and peptidase, was not impaired by acylation.     

Storage and Bacterial Contamination Effects on Myofibrillar Proteins and Shear Force of Beef

Thirty-two steaks from the longissimus muscle, fifth rib to third lumbar vertebra, were obtained from youthful carcass beef. Half were sterilized by ultraviolet light and all vacuum packaged and stored for 1, 14, 28 or 57 days at 2°C. After storage, steaks were examined for microbial populations, myofibril fragmentation index (MFI), cooking characteristics and shear force (SF). Aerobic and anaerobic counts decreased during storage. Psychrotrophic counts were low throughout. Sterilization had no effect on SF or MFI. Cooking loss tended (P < 0.09) to increase with time of storage. SF values decreased and MFI values increased through day 14, but remained relatively constant after that. Results of SDS-PAGE, SF and MFI indicate major changes in proteolysis of myofibrils and tenderness were completed by day 14.     

大足黑山羊宰后成熟过程中肌原纤维蛋白功能性质的变化

以大足黑山羊后腿肉为原料,研究羊肉宰后成熟过程中肌原纤维蛋白（myofibrillar protein,MP）功能性质的变化。结果表明：随着宰后成熟时间的延长,羊肉MP的溶解度、乳化活性指数和乳化稳定性均呈先下降后上升的趋势,且在宰后24 h达到最小值;表面疏水性、凝胶硬度和弹性及凝胶蒸煮损失均呈先增加后下降的变化趋势,且在宰后24 h达到最大值。综合各项指标的变化规律,从羊肉加工性能的角度考虑,大足黑山羊羊肉的最佳成熟时间为72 h。     

3种鱿鱼冻藏过程中肌原纤维蛋白功能特性变化

为探讨阿根廷鱿鱼、北太平洋鱿鱼(以下简称北太鱿鱼)和秘鲁鱿鱼冻藏过程中肌原纤维蛋白功能特性的变化情况.将3种鱿鱼于-18℃C冰箱中冻藏,分别于0、15、30、45、60、75、90、105 d和120 d进行取样,分析测定鱿鱼肌肉中肌原纤维蛋白质量浓度、溶解性、浊度、乳化能力、Ca2+-ATPase活力、起泡性及泡沫稳...     

籽瓜种子蛋白对肌原纤维蛋白功能的影响

本研究以籽瓜种子为原料,利用碱溶酸沉方法提取籽瓜种子蛋白,在40、60、80℃条件下获得不同籽瓜种子蛋白,分别进行分子质量、溶解度测定,并与肌原纤维蛋白形成凝胶,对凝胶作用力、弹性、回弹性、粘结性、水相分度、白度进行试验。结果表明,40~80℃范围内随着提取温度的升高,籽瓜种子蛋白溶解度先升高后降低差异显著(P0.05),并获得4个吸收峰,峰1为699~103ku的大分子蛋白聚集体,峰2、峰3分别为340、212 ku的球蛋白,及10~54 ku部分清蛋白、球蛋白的亚基,随着碱溶温度继续升高,峰2、峰3逐渐消失。籽瓜种子蛋白与肌原纤维蛋白形成凝胶的三维网状结构稳定性通过疏水键、氢键、以及二硫键维持,其中疏水键、氢键为主要作用力。碱溶温度为60℃时,WPS与MP形成凝胶弹性较好、保水性较好,差异显著(P0.05)。随着温度的增加,凝胶白度逐渐加,WPS结构发生改变、变性,差异显著(P0.05)。由此可知,温度对籽瓜种子蛋白结构、功能影响较大,不同碱溶温度提取的籽瓜种子蛋白对肌原纤维蛋白功能影响差异显著,碱溶温度为60℃时,获得籽瓜种子蛋白与肌原纤维蛋白形成的凝胶有利于改善对肉制品品质,可作为非肉蛋白稳定剂添加到猪肉制品中。     

肌原纤维蛋白热诱导凝胶特性研究进展

肌原纤维蛋白质是肌肉中一类重要的结构蛋白质群,它对于肉食制品的品质和特性具有非常重要的影响.肌原纤维蛋白的凝胶特性是形成肉制品独特的质构、保水性、乳化性以及感官特性的决定性因素.本文介绍了肌原纤维蛋白凝胶机制、功能特性及其影响因素,为进一步了解肉制品加工特性提供一定理论指导.     

芬顿氧化体系处理对白斑狗鱼肌原纤维蛋白结构和功能特性的影响

研究芬顿氧化体系诱导的不同氧化水平(0、1、5、10、20?mmol/L?H2O2)对白斑狗鱼肌原纤维蛋白结构和功能特性的影响.随着氧化水平的升高,肌原纤维蛋白的羰基和浊度增加、溶解度显著降低(P<0.05).十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析结果显示氧化后的肌原纤维蛋白中产生更多交联和蛋白质聚合.傅里叶变换红外光...     

不同漂洗处理后冻藏对鲤鱼蛋白功能特性的影响

蛋白质氧化是引起食品加工及贮藏过程中品质发生劣变的一个主要原因。本文以鲤鱼肉为研究对象,主要研究鱼糜加工过程中经不同漂洗处理后冻藏对鲤鱼肌原纤维蛋白功能特性的影响。把鱼肉经不同方式漂洗[未漂洗;传统漂洗;添加抗坏血酸钠漂洗;添加没食子酸丙酯(PG)漂洗]后置于-25℃,经不同时间(0、30、60、90、120 d)冷冻贮藏后,利用质构仪、电子显微镜、流变仪等设备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,结果表明冻藏过程中发生的蛋白质氧化会引起鲤鱼肌原纤维蛋白各项功能特性降低,在漂洗过程中加入PG处理的鱼肉功能特性改变最小,说明添加PG漂洗可以有效地抑制蛋白质氧化的发生,从而减少鲤鱼肌原纤维蛋白功能特性的改变。     

Gelation of Crude Myofibrillar Protein Isolated From Beef Heart Under Antioxidative Conditions

Oxidation inhibition during washing, as it affects gelling properties and binding strength of beef heart myofibrillar protein, was investigated. Crude myofibrils isolated by repeated washing in the presence of propyl gallate, ascorbate and tripolyphosphate had a lower TBA value and formed stronger gels (puncture and compression strengths) in the pH range 5.8–7.0 and in 0.6M NaCl than the control myofibrils. Inhibition of oxidation increased tensile stress of myofibrillar gels and enhanced bind strength in restructured meat. Functionality of myofibrillar protein could be protected by antioxidants used in the washing process.     

低磁场冷冻对鲢鱼肌原纤维蛋白的作用

采用2mT低磁场（low magnetic field,LMF）冷冻、0mT磁场（no magnetic field,NMF）冷冻和常规冷冻（conventional freezing,CF）技术对3 组鲢鱼肌原纤维蛋白进行为期28 d的冷冻实验。通过表面疏水性、巯基含量、溶解度、浊度、热稳定性、傅里叶变换红外光谱、内源性荧光光谱和紫外吸收光谱各项指标考察蛋白的结构和功能性质变化。结果表明：施加低磁场冷冻可以抑制蛋白聚集和内部疏水基团的暴露,且能抑制α-螺旋的展开,减弱α-螺旋向β-折叠转变的能力,并维持良好的二、三级结构稳定性;CF组的蛋白总巯基含量、溶解度和浊度与NMF组相比无显著差异,由于冷冻温度较低,对蛋白聚集和内部疏水基团的暴露有一定的抑制作用,同时也使得蛋白结构变得松散不稳定;与CF组相比,LMF组同样显示出对蛋白的结构和功能有较好的保护和改善作用。总体来说,低磁场冷冻可以抑制肌原纤维蛋白变性并维持良好的结构和功能,且与常规冷冻（－30 ℃）相比,低磁场冷冻（－20 ℃、2 mT）可以节约10 ℃的冷冻温差,预测其具有一定的节能潜力。     

Effect of Oxidation on the Emulsifying Properties of Myofibrillar Proteins

The aim of this work was to investigate the effect of chemical oxidation on the emulsifying properties of myofibrillar proteins. Myofibrillar proteins were oxidized by a hydroxyl radical generating system (Fenton reaction). Structural changes of oxidized or non-oxidized myofibrillar proteins were determined using surface hydrophobicity (H₀) and Fourier transform infrared (FTIR) spectroscopy. The results suggested that H₀ increased (p?<?0.05) after treatment with oxidizing agent. Result from FTIR suggested that protein aggregation occurred and there was an increase in β-sheet structure accompanied by a decrease in turns, alpha helix, and random structures with the increase of oxidizing agent. Changes in zeta potential of the test emulsions suggested that protein oxidation could alter the electric charge of myofibrillar proteins. The analysis of the emulsions showed that protein oxidation had a negative effect on the emulsifying properties of myofibrillar proteins due to changes in electric charge, surface active properties, and protein molecular flexibility.