Effect of salt addition on the thermal behavior of proteins of bovine meat from Argentina

Research was undertaken to investigate how the addition of sodium chloride (NaCl) and/or sodium tripolyphosphate (TPP) to sous vide cooked meat pieces produces an increase in water holding capacity (WHC). Semitendinosus muscles were injected to obtain tissue final concentrations of 0.70% NaCl, 0.25% TPP, 0.70% NaCl+0.25% TPP, and 1.20% NaCl+0.25% TPP. SDS-PAGE analysis showed increased protein solubilization in those treatments which included NaCl. Thermal analysis of whole muscles and isolated myofibrils showed the destabilizing effect of NaCl and a global stabilizing effect of TPP. Both salts together induced a destabilizing global effect, where TPP assisted NaCl in breaking the meat structure. It is suggested that the WHC increments are related to conformational changes in myofibrillar proteins and to the weakening of myofibrillar structure by the removal of myofibrillar proteins.     

The relationship between water-holding capacity and cooked meat tenderness in some beef muscles as influenced by acidic conditions below the ultimate pH

Previous studies have indicated the beneficial influence of higher than normal ultimate pH (pH(u)) on the tenderness of cooked meat. Such benefits have been indirectly linked to the influence of increased pH on the water-holding capacity (WHC) of meat above the iso-electric point (IEP) of the myofibrillar proteins. In the present study, relationships between WHC and the tenderness of some beef muscles were investigated under pH conditions within and below the IEP of the myofibrillar proteins, such that the maximum range of meat swelling was achieved. It was found that increased WHC, as measured by swelling ratio in both raw and cooked meat, markedly influenced cooked meat tenderness, irrespective of the connective tissue content of the muscles. The results fitted a series of exponential decay equations relating swelling ratio to cooked meat toughness. Additionally, strong linear decreases in toughness were apparent over the pH range 4·6 to 4·1 for the three muscle types studied.     

微冻贮藏对牛肉保水性的影响

本实验以冷藏（2 ℃）和冷冻（－18 ℃）作为对照组,从肌原纤维蛋白结构和水分迁移等方面分析了微冻（－4 ℃）贮藏条件下牛肉保水性变化的机制。结果表明：微冻贮藏牛肉的汁液损失率和蒸煮损失率显著高于冷藏和冷冻处理组（P＜0.05）,保水性最差。微冻贮藏过程中,牛肉中的水分弛豫时间逐渐变长,结合水相对含量无明显变化,不易流动水相对含量显著下降,自由水相对含量显著上升（P＜0.05）。随着贮藏时间的延长,3 种贮藏方式下牛肉的总巯基含量和活性巯基含量均显著下降,蛋白质表面疏水性显著上升（P＜0.05）,且贮藏温度越低,变化速率越慢。微冻贮藏过程中,牛肉肌原纤维蛋白降解程度较低,贮藏后期蛋白质变性程度较高,提升了肌原纤维蛋白网络中不易流动水的自由度,使得部分不易流动水转化为自由水,导致了微冻牛肉较差的保水性。     

Effect of sodium chloride concentration on pH, water-holding capacity and extractable protein of prerigor and postrigor ground beef

Fifteen beef cattle of similar age and management history were randomly allotted by slaughter days into three groups. Paired sternomandibularis were removed immediately following bleeding and trimmed of visible fat and connective tissue. They were randomly labelled as prerigor and postrigor and assigned to a 0, 0·5, 1·0, 2·0 or 4·0% NcCl treatment. Water-holding capacity (WHC), pH, the ratio of absorbance at 250 nm over the absorbance at 260 nm (R-values), and 1·0m NaCl extractable protein (EP) were monitored over treatment times. The 0 h samples were defined as when the NaCl was incorporated with the muscle. R-values verified that 0 h samples were in the prerigor or postrigor state. Ultimate pH remained higher (P < 0·05) in prerigor homogenates with increasing NaCl concentration. EP and WHC were higher (P < 0·05) in prerigor than in postrigor homogenates with 2 and 4% NaCl at all time periods. Prerigor homogenates containing 0·5 and 1·0% NaCl had higher (P < 0·05) WHC at 12, 24, 24, 48 and 96h than similarly treated postrigor homogenates and as high or higher WHC than any postrigor treatment. Results of this study indicate an advantage to using low NaCl concentrations in prerigor salted beef.     

Bone and Plasma Protein Extracts in Sausages

Proteins from bones were extracted (4°C) at pH 10 and emulsifying capacity (EC) of bone protein extracts (BPE) were compared with beef muscle (BMP) and blood plasma (PP) proteins. PBE showed the lowest EC (ml oil/g total protein) values but they were similar to BMP when the EC was calculated on a soluble protein basis. EC values from BPE were enhanced by mixing those proteins with BMP. Sodium-pyrophosphate improved EC values primarily at low protein concentrations. Water-holding capacity (WHC) of the BPE, BMP and PP were obtained and a close correlation (r = 0.99) was found between WHC and the fat/protein ratio of the samples. Up to 10% BPE plus 5% PP and both plus 0.4% of sodium pyrophosphate were included in the manufacture of cooked sausages. These products were ranked as acceptable by a sensory panel.     

养殖暹罗鳄肉肌原纤维蛋白的理化性质

筛选养殖暹罗鳄肌原纤维蛋白含量最高部位,提取并分析离子强度、pH值和温度对肌原纤维蛋白溶液的溶解性、乳化性和热诱导凝胶特性的影响。结果表明：暹罗鳄尾部肌原纤维蛋白所占比例最高（（7.95±0.12） g/100 g,以湿质量计）,暹罗鳄尾肉中肌原纤维蛋白主要为肌球蛋白重链、副肌球蛋白、肌动蛋白和原肌球蛋白。在低离子强度条件下,肌原纤维蛋白的溶解度和乳化性较低,但有良好的凝胶特性,随着离子强度的升高,肌原纤维蛋白的溶解度和乳化性升高,凝胶特性则呈现下降趋势。随着pH值升高,肌原纤维蛋白溶解度呈现先迅速下降后升高的趋势,乳化性和凝胶特性则呈现持续缓慢下降的趋势,其中溶解度和保水性在pH 5.5达到最低点。随着热变温度升高,其凝胶特性显著增加,保水性先下降后略有升高,在低温（40 ℃）下有较好的保水性,在80 ℃保水性升高至又一峰值随后下降。结论：肌原纤维蛋白在NaCl浓度0.2 mol/L进行调配,并在80 ℃条件下加热处理,暹罗鳄肉类产品将具有较好的质构特性及保水性。     

Timed Emulsification Studies with Chicken Breast Muscle: Soluble and Insoluble Myofibrillar Proteins

Emulsion formation with chicken breast muscle was investigated using timed emulsification. High-salt soluble proteins (pH 7.0, 0.6M NaCl) extracted from previously washed muscle (pH 7.0, 0.05M NaCl) were removed from the aqueous phase as mixing time increased. Low- and high-salt exhaustively washed muscle, resuspended in either 0.15 or 0.6M NaCl, pH 7.0, still exhibited good emulsion properties. The pellet protein decreased (> 90%) as mixing time increased from 0 to 5 min. Addition of sodium pyrophosphate to 0.6M NaCl suspensions of 0.05M NaCl washed muscle resulted in an increase in solubility of myofibrillar proteins and a general improvement in emulsification properties. High-salt insoluble proteins may play an important role in emulsion formation.     

Protein Extraction From Chicken Myofibrils Irrigated with Various Polyphosphate and NaCl Solutions

Physical changes in chicken gastrocnemius myofibrils incubated in 0.1 to 1.0 M NaCl solutions with or without 10 mM ortho-(P), pyro-(PP), tripoly-(TPP) or hexameta- (HMP) phosphate at pH 6.0 were examined by phase-contrast microscopy, electrophoresis, and solubility. PP and TPP performed similarly in promoting protein extraction, P had no apparent effect, and HMP exhibited an intermediate effect. PP, TPP, and HMP treatments markedly improved protein solubility in 0.3 and 0.4 M NaCl through the release of myosin, but the phosphate effect diminished in ≥ 0.6 M NaCl. Overall, phosphates influenced the ultrastructure of myofibrils and extraction of their constituents in the order: PP ∼ TPP > HMP > P ∼ nonphosphate control.     

谷氨酸螯合钙替代部分食盐对兔肉肌原纤维蛋白热凝胶和乳化特性的影响

为降低凝胶类低温肉制品中的钠离子含量,研究谷氨酸螯合钙替代部分食盐对兔肉肌原纤维蛋白加工特性的影响。从兔腰大肌中提取肌原纤维蛋白,添加质量分数为1.25%的谷氨酸螯合钙,再分别添加0.4%、0.8%、1.2%、1.6%、2.0%的食盐（食盐组成为70%NaCl和30%KCl）,研究肌原纤维蛋白流变特性、保水性、乳化活性和乳化稳定性以及乳化体系复合热凝胶的保油保水性变化,并以3%食盐组作为对照。结果表明：食盐添加量增多,肌原纤维蛋白热凝胶储能模量（G’）增大,1.2%食盐组G’值高于对照组（P＜0.05）;但是凝胶保水性先增强后减弱,1.2%食盐组保水效果最好。食盐添加量增多,乳化活性增大;而乳化稳定性以0.8%和1.2%食盐组最高,与对照组差异不显著（P＞0.05）。1.2%和1.6%食盐组的保油保水性显著高于对照组（P＜0.05）。结论：添加谷氨酸螯合钙可以使兔肉肌原纤维蛋白形成具有良好黏弹性和保油保水性的低钠热凝胶,凝胶类低温肉制品的NaCl添加量可以减至0.84%。     

不同冻结温度下牛肉的肌原纤维蛋白变性与肌肉持水性

为明确冷冻温度对牛肉肌原纤维蛋白变性和肌肉持水性（water-holding capacity,WHC）的影响、探讨肌 原纤维蛋白变性与WHC的相关性。以牛背最长肌作实验材料,探究－9、－18、－23、－38 ℃下冻结后肌原纤维 蛋白理化特性和牛肉WHC。通过测定巯基含量、蛋白质溶解度、Ca2＋-三磷酸腺苷酶（adenosine triphosphatase, ATPase）活力及蛋白质热稳定性考察牛肉冻结后肌原纤维蛋白变性情况,利用解冻汁液流失与加压失水率指标衡 量牛肉WHC,采用低场核磁共振（low field-nuclear magnetic resonance,LF-NMR）波谱和磁共振成像（magnetic resonance imaging,MRI）技术对比分析了肌肉水分分布情况,并于4 ℃解冻后测定了色差与剪切力。结果表明： －23 ℃与－38 ℃下冻结试样较－9 ℃与－18 ℃肌原纤维蛋白变性程度小：－23 ℃与－38 ℃下冻结试样蛋白质溶解 度、Ca2＋-ATPase活力、巯基含量和总变性焓相比－9 ℃与－18 ℃实验组较高（P＜0.05）。－23 ℃与－38 ℃下冻 结牛肉解冻后L*值、b*值、剪切力、解冻汁液流失和加压失水率显著低于－9 ℃与－18 ℃（P＜0.05）。LF-NMR 及MRI结果相互佐证了肉样在－23 ℃与－38 ℃冻结下肌肉WHC高于－9 ℃与－18 ℃的实验结果。肌原纤维蛋白理 化特性（蛋白质溶解度、Ca2＋-ATPase活力、巯基含量、总变性焓）与WHC（解冻汁液流失率、加压失水率）均呈 极显著相关（P＜0.01）,L*、b*值及剪切力亦与WHC存在极显著相关（P＜0.01）。相关性分析结果验证了牛肉冻结 过程中肌原纤维蛋白变性对肌肉持水性存在显著影响,进而导致牛肉解冻后出现肉色劣变、嫩度下降及汁液流失。     

发酵对牛肉嫩度影响及机理分析

研究发酵对牛肉嫩度改善及机理。半腱肌切成5cm×5cm×3cm肉块,添加3.0% NaCl、2.0%葡萄糖和0.020%乳酸菌粉(lg(14CFU/g)),搅拌均匀,10℃隔氧发酵。0、2、4、6d分别对肉样进行理化分析。结果表明：随着发酵时间延长,肉样pH值和剪切力显著降低(P＜0.05),原子力纤维镜观察肌原纤维碎片显著增多;SDS-PAGE结果显示肌原纤维24kD蛋白降解。发酵可降解牛肉肌原纤维蛋白,改善牛肉嫩度。     

Effects of chicken myofibrillar protein concentration on protein oxidation and water holding capacity of its heat-induced gels

The effects of chicken myofibrillar protein (MP) concentrations (20, 40 and 60 mg/mL) on MP oxidation and the subsequent effects on water holding capacity (WHC) of heat-induced gels were investigated. MP oxidation stressed by a hydroxyl radical-generating system (10 µM FeCl₃, 0.1 mM ascorbic acid, and 1 mM H₂O₂) was evaluated by carbonyl content. Water distribution, microstructure visualization, free sulfhydryl (FSH) groups and molecular forces of the gels were determined to illustrate the effects on WHC. Compared to the non-stressed group, the stressed proteins were highly oxidized where the carbonyl content (p?<?0.01) increased with decreasing MP concentrations (increased by 24.67% at 20 mg/mL). As the MP concentrations were decreased, the percentage of immobile water (decreased by 8.01% at 20 mg/mL, while increased by 5.98% at 60 mg/mL), ionic bonds, hydrogen bonds, and FSH groups (p?<?0.05) of the oxidized gels were decreased, the gel network of the oxidized groups was impaired which was with more cracks and protein aggregates, the hydrophobic interactions (increased by 24% at 20 mg/mL) and the percentage of free water (p?<?0.05) (increased by 7.80% at 20 mg/mL, but decreased by 6.13% at 60 mg/mL) of the oxidized gels were enhanced, and the resultant WHC was reduced (decreased by 17.75 and 8.07% at 20 and 40 mg/mL, respectively, but increased by 8.54% at 60 mg/mL). The results indicated that the MP concentration could be a potential influencing factor that affected the protein oxidation and subsequently affected the WHC of gels.     

Postmortem Degradation of Titin and Nebulin of Beef Steaks Varying in Tenderness

Purified myofibrils were isolated from “tender” and “less-tender” bovine longissimus muscle at death and at 1, 3, 7, and 14 days of postmortem storage (4^oC). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used to detect changes in the myofibrillar/cytoskeletal proteins, titin and nebulin. Titin and nebulin bands were observed to be less intense on gels from “tender” than from “less-tender” steaks. These results suggest that titin and nebulin were more rapidly degraded in “tender” than in “less-tender” steaks, and that the extent of beef loin steak tenderness may be dependent upon the postmortem degradation of titin and nebulin.     

FACTORS AFFECTING THE SODIUM CHLORIDE EXTRACTABILITY OF MUSCLE PROTEINS FROM CHICKEN BREAST, TROUT WHITE AND LOBSTER TAIL MUSCLES

The amount of protein extracted from chicken breast muscle at low salt (0–50 mM NaCl) increased as the salt concentration of the extracting solutions increased. The addition of 10 mM sodium phosphate buffer pH 7 (P_i) caused a marked increase in protein extractability at all salt concentrations. A particular polypeptide chain of about 150,000 daltons appeared to be particularly sensitive to the extraction conditions. At high salt (0.6M NaCl, 50 mM sodium phosphate buffer pH 7.0) a second extraction still contained significant amounts of protein. The amount of protein extracted was maximized at a 1/20 dilution. On the other hand, the protein extract-ability of trout white muscle, showed a smaller P_i effect and very little dependence on low salt concentration. The protein extractability of lobster flexor muscle showed little change with either increased salt or P_i. For all three muscles extraction over time with either high or low salt remained essentially constant after the first day with the most protein being extracted from lobster muscle and the least from chicken muscle.     

Extraction of Proteins from Pacific Whiting Mince at Various Washing Conditions

Effects of salt concentrations and washing cycles on the extraction of proteins were evaluated. Sarcoplasmic proteins were readily soluble in water (0% NaCl) and removed in the initial washing steps. Myofibrillar proteins became relatively soluble and were lost during extensive washing. Control of water/meat ratio, washing time, and washing cycles was critical in reducing the loss of myofibrillar proteins. Washing with 0.25%, 0.5%, and 1.0% NaCl solutions reduced the loss of myofibrillar proteins. However, these solutions were not very effective in removing sarcoplasmic proteins even with increased washing cycles. High salt (2.0% NaCl) washing resulted in low removal of sarcoplasmic proteins and severe loss of myofibrillar proteins.     

Interactive Effects of Factors Affecting Gelation of Whey Proteins

The individual effects of heating time (15–120 min), pH (3–9) and NaCl (0–2M), sucrose (0–30% w/v) and protein (10–30% w/v) concentrations on the strength, turbidity and water holding capacity were investigated on a commercial whey protein concentrate (WPC, 75% protein) when heated at temperatures ranging from 65 to 90°C. Interactive effects were investigated using a four-variable, five-level central composite rotatable design (CCRD) analyzed by response surface methodology (RSM). Gel strength (GS) and water holding capacity (WHC) increased with protein concentration, heating temperature and time. Increasing sucrose concentration decreased GS but increased WHC. Increasing NaCl concentration increased GS and WHC below pH 5 but resulted in weaker gels at high pH (>7).     

提取条件对鲨鱼肉盐溶蛋白热诱导凝胶特性的影响

以鲨鱼肉为材料,研究NaCl 浓度、pH 值、静置提取时间及加热时间对鱼肉盐溶蛋白热诱导凝胶保水性和质构特性的影响。结果表明：鲨鱼肉盐溶蛋白凝胶的保水性、硬度、弹性和黏聚性与NaCl 溶液浓度呈正相关;在NaCl 溶液浓度0.8mol/L、pH6.5～7.0、静置提取时间24h、40℃加热40～60min 时形成的凝胶保水性及其质构指标较理想;40℃加热盐溶蛋白,有利于形成凝胶结构,但随着加热时间的延长,盐溶蛋白凝胶硬度增加,保水性降低。     

Variations in water-holding capacity due to changes in the fibre diameter, sarcomere length and connective tissue morphology of some beef muscles under acidic conditions below the ultimate pH

The water-holding capacities (WHC) of six different beef muscles were measured over the pH range 5·7 to 4·0. Corresponding changes in the morphology of muscle fibres and connective tissue were observed by light microscopy. WHC increased over the pH range 5·1 to 4·0 in all muscles, with the M. longissimus dorsi (LD) having significantly higher (p < 0·05) swelling ratios than the other muscles at pH 4·3 and pH 4·0. In all muscles, swelling increased across and along the muscle fibre axis between pH5·1 and pH4·4. However, towards pH4·0, increased muscle fibre swelling occurred in predominantly 'white' fibre-type muscles, in particular the LD, whereas muscle fibre shrinkage occurred in predominantly 'red' fibre-type muscles. Increased swelling of perimysial collagen and endomysial reticulin was observed in all muscles between pH4·5 and pH4·0, while the appearance of elastin was unaffected by pH. Consequently, interactions between muscle fibre swelling and connective tissue swelling determined the extent of total muscle swelling in different muscles between pH 4·5 and pH 4·0.     

Effect of reduced sodium chloride concentration and tetrasodium pyrophosphate on pH, water-holding capacity and extractable protein of prerigor and postrigor ground beef

The effect of tetrasodium pyrophosphate (TSPP) (0, 0·25, 0·5% w/w) alone or in combination with salt (NaCl) (0, 0·5, 1·0% w/w) on water-holding capacity (WHC), pH, the ratio of absorbance at 250 nm over the absorbance at 260 nm (R-values) and 150m CaCl extractable protein (EP) was studied in prerigor and postrigor sternomandibularis homogenates over time. The 0 h samples were defined as when the NaCl was incorporated with the muscle. R-values verified that 0 h samples were in a prerigor or postrigor state. In prerigor homogenates, increasing phosphate concentration increased the time required to reach ultimate pH. Ultimate pH values of prerigor homogenates containing phosphate were lower (P < 0·05) than homogenates without phosphate and similarly treated postrigor homogenates. After six hours, no differences (P > 0·10) were noted in EP or WHC at different phosphate concentrations when averaged over NaCl concentrations in prerigor homogenates. With increasing phosphate concentration of postrigor homogenates, there was an increase (P < 0·05) in pH and EP at the initial sampling time. However, 0 and 0·25% phosphate WHC values could not be differentiated (P > 0·10). Results of this study indicate no advantages, after six hours post mortem, to using TSPP alone or in combination with NaCl in prerigor meat homogenates at concentrations added in this study.     

A Sensory Panel and Chemical Analysis of Certain Beef Chuck Muscles

Sensory panel and Warner-Bratzler Shear (WBS) values of nine muscles (biceps brachii, complexus, deep pectoral, infraspinatus, longissimus, rhomboideus, serratus ventralis, supraspinatus and triceps brachii) from the beef chuck. The deep pectoral, infraspinatus and rhomboideus were used to determine myofibril fragmentation index (MFI), and the infraspinatus and rhomboideus were used to study myofibrillar protein degradation. The infraspinatus was scored the most tender and palatable, and the rhomboideus was scored least tender and palatable. Greater protein degradation differences were observed in myofibrils isolated from the infraspinatus muscle than in those from the rhomboideus for the proteins titin, nebulin and troponin-T.