宰后成熟对牛胴体不同部位显微结构影响

将不同部位肉样真空包装后于4℃条件下成熟72h ,采用石蜡切片苏木精-伊红(HE)染色法、原子力显微镜扫描肌原纤维、环境扫描电镜扫描肌纤维膜、免疫组织化学法及测定剪切力,研究牛胴体不同部位剪切力、宰后成熟过程中肌纤维和肌原纤维裂解程度、肌纤维膜变化及μ-calpain肌纤维定位。结果表明：剪切力：半腱肌＞腹直肌＞背最长肌;牛肉后熟过程中,背最长肌肌纤维、肌原纤维裂解程度最大,腹直肌次之,半腱肌变化较小;肌纤维膜变化不大;μ-calpain主要存在于肌纤维膜和肌浆中,红肌纤维(慢肌)μ-calpain含量高,白肌纤维(快肌)μ-calpain含量低。μ-calpain在牛肉后熟过程中对牛肉嫩化具有重要作用,红肌纤维μ-calpain含量高,白肌纤维μ-calpain含量低,因此,胴体不同部位红肌纤维和白肌纤维的比例是导致其后熟嫩度和显微结构差异较大的一个重要因素。     

牛肉排酸成熟过程中的品质变化

为探究排酸成熟过程中肉类品质的变化,以牛肉为研究对象,测定排酸1～7 d肉样的硬度、保水性、pH值、肌原纤维小片化指数（myofibril fragmentation index,MFI）、菌落总数、大肠菌群数以及排酸1、3、5d时肌原纤维的超微结构。结果表明：牛肉排酸3 d时出现最大僵直期,硬度达到最高,保水性达到最低,pH值降到最低值5.56;随着解僵及成熟的进行,牛肉嫩度、保水性回升,排酸7 d时pH值回升到5.84,达到排酸成熟肉标准（5.8～6.2）;排酸1 d时,肌原纤维的Z线、粗细丝清晰可见,随着肌原纤维小片化程度的不断加深,排酸5d时,Z线变得模糊,几乎消失,成为晕染状,几何构型发生明显变化。上述结果表明,牛肉在0～4 ℃条件下排酸成熟需要7d,前3 d是排酸的关键时期。     

宰后成熟期间结构蛋白对秦川牛肉嫩度的影响

为探究宰后成熟期间结构蛋白对秦川牛背最长肌嫩度的影响,测定不同贮藏期（0、2、4、6、8 d）内秦川牛背最长肌剪切力、肌原纤维小片化指数（myofibrillar fragmentation index,MFI）和蛋白含量等,并利用4D-非标记定量（4D-label free quantification,4D-LFQ）蛋白质组学技术分析蛋白质组学变化。结果表明：在贮藏期0～8 d内,剪切力总体呈先升后降的趋势（P＜0.01）,上升的幅度小于下降的幅度;秦川牛背最长肌MFI呈极显著上升趋势（P＜0.01）,总体增长了250.81%;总可溶性蛋白含量呈显著下降趋势（P＜0.05）,总体下降了34.60%;通过宰后肌肉组织代谢变化,肌肉组织结构蛋白发生降解,可能会影响到嫩度的形成,肌原纤维蛋白含量呈显著下降趋势（P＜0.05）,前期下降速度较快,后期下降速度减缓,总体下降了50.56%。在贮藏期0～4 d内,通过骨骼肌组织发育过程调控钙离子结合和细胞骨架蛋白结合途径,4 种蛋白（α-肌动蛋白-1、牛肌球蛋白重链9、牛肌球蛋白轻链2、肌球蛋白调节轻链12B）丰富度发生变化;在贮藏期0～8 d内,通过肌肉器官发育和横纹肌组织发育过程调控钙离子结合途径,8 种蛋白（肌球蛋白调节轻链2、肌球蛋白重链6、α-肌动蛋白-1、心肌肌动蛋白α1、牛肌球蛋白轻链2、肌钙蛋白I 1型、肌钙蛋白I 2型、肌球蛋白重链15）丰富度发生变化,通过肌球蛋白结合、钙离子结合、细胞骨架蛋白结合的肌原纤维组装、骨骼肌组织发育、肌肉器官发育、横纹肌组织发育过程等途径调控细胞的生理状态,结构蛋白降解造成肌原纤维小片化升高,进而促使嫩度提升。     

成熟时间和斩拌时间对低盐牛肉丸品质的影响

以牛后腿肉为原料制作牛肉丸,采用均匀设计探讨宰后成熟时间、斩拌时间和食盐添加量对肉丸质构 特性、出品率和感官品质的影响。结果表明：3 个因素对牛肉丸的质构特性、出品率和感官评分均有显著影响 （P＜0.05）。牛肉丸的弹性随宰后成熟时间的延长先降低后升高;牛肉丸的回复力随着宰后成熟时间的延长或食 盐添加量的增加逐渐变大,随着斩拌时间的增加先上升后下降;牛肉丸的硬度随着宰后成熟时间的延长先下降后上 升,随着斩拌时间的增加逐渐下降,随着食盐添加量的增加逐渐增大。牛肉丸的出品率和感官评分均随宰后成熟时 间的延长而下降,低盐条件下下降尤为明显。因此,对于低盐牛肉丸的生产,宰后越早加工,牛肉丸的品质越好。     

Reducing Postmortem Aging Time of Beef with Electrical Stimulation

Two studies (Study 1 = 23 forage-fed steers; Study 2 = 20 grain-fed steers and heifers) were conducted to determine relationships of electrical stimulation (ES) and/or postmortem aging (PA) to tenderness of beef. For Study 1, steaks from ES sides had lower (P < 0.05) Warner-Bratzler shear (WBS) values than steaks from not-ES sides for each PA period. In addition, the percentage reduction in WBS values was greater for the steaks from the ES-Day 2 group (–29.5%) than for steaks from even the longest PA period (14 days) from the not-ES group (–25.8%). For Study 2, during the fist three PA periods (1, 2 and 5 days), ES resulted in more desirable (P < 0.05) flavor ratings (Day l), higher (P < 0.05) tenderness ratings and lower (P < 0.05) WBS values (Day 1, 2, 5) and more desirable (P < 0.05) overall palatability ratings (Day 1, 2). During the last three PA periods (8, 11 and 14 days), ES resulted in higher (P < 0.05) tenderness ratings (Day 8), lower (P < 0.05) juiciness ratings (Day 11, 14) and lower (P < 0.05) WBS values (Day 8). Based on these results, ES had the greatest impact on beef palatability if the period of aging was 8 days or less; with additional aging time, ES effects on palatability were negated. When each treatment (ES, not-ES) was divided into two groups based on median tenderness ratings for the not-ES group, ES had the greatest impact on those carcasses in the “tough” group while ES had little impact on those carcasses in the “tender” group. ES will accelerate the postmortem aging of beef but the aging time reduction and extent of ultimate tenderization appears to be affected by the inherent tenderness of the beef.     

Enzyme Activity Levels in Beef: Effect of Postmortem Aging and End-point Cooking Temperature

While it is known that meat flavor varies as a function of end-point cooking temperature, storage time, and activity of endogenous hydrolytic enzymes, little is known about the interrelationship of these three factors with flavor. Several endogenous enzymes and proteins with potential involvement in meat flavor were investigated. The data indicate two main observations: (1) enzymes are redistributed to new intracellular compartments during postmortem aging. (2) enzyme activity is temperature dependent over the range examined (20-80°C) with some enzymes such as cathepsins B & L retaining a high level of activity (>20% of that at 20°C) at temperatures above 70°C. Thus, the combined effect of postmortem aging and cooking, via enzyme redistribution and enzyme activity, respectively, influence the production of flavor compounds and precursors.     

Effect of Temperature on Collagen Extractability and Kramer Shear Force of Restructured Beef

Collagen extractability and Kramer shear force were measured for raw and heated restructured beef products made with trimmed (epimysium removed) and untrimmed clods (triceps brachii, infraspinatus, and supraspinatus). Collagen extractability was significantly (p < 0.001) higher for untrimmed samples heated at 50°C than for trimmed samples. Kramer shear forces were significantly higher (p < 0.01) for untrimmed than trimmed when raw or heated at 35°C, 45°C, WC, and 55°C. Collagen extractabilities showed no distinct changes with temperature for trimmed samples. Collagen extractability of untrimmed samples increased then decreased as heating temperature increased. Kramer shear forces decreased between 55°C and 60°C for both trimmed and untrimmed samples.     

NO对宰后牛肉成熟过程中AMPK活性、糖酵解及持水力的影响

为研究宰后牛肉中NO对一磷酸腺苷活化蛋白激酶(AMP-activated proteinkinase,AMPK)活性、糖酵解及肉品持水力的级联调控作用.以NO释放剂二乙烯三胺(diethylenetriamine,DETA)、一氧化氮合成酶抑制剂亚硝基左旋精氨酸甲酯(L-nitro-arginine methyl es...     

宰后颈臂束缚技术对牛肉品质的影响

颈臂束缚技术是一种在跟腱吊挂基础上,于牛胴体前臂远端与颈前端之间施加一径向外力使之收紧,从而 加快肉牛胴体成熟的技术。为研究该技术对牛肉品质的影响,选取6 头年龄和活体质量相近的新疆褐牛,屠宰后左 半侧胴体采用颈臂束缚技术成熟（实验组）,右半侧胴体采用传统跟腱吊挂方式成熟（对照组）,分别于宰后0、 1、2、3、7、14、21 d测定牛臂三头肌、背最长肌和股二头肌三部位的pH值、失水率、蒸煮损失率、剪切力和肌纤 维超微结构等指标。结果表明：与对照组相比,实验组肉样失水率增加、剪切力降低、肌原纤维小片化指数增大, 且差异显著,肌原纤维结构破坏更为严重。颈臂束缚成熟技术可以缩短牛肉的宰后成熟时间,降低工厂生产成本, 提高生产效率。     

Accelerated Postmortem Aging of Beef Utilizing Electronbeam Irradiation and Modified Atmosphere Packaging

The combined effects of electron-beam irradiation and modified atmosphere packaging (MAP) with 25% CO₂ and 75% N₂ were examined. Steaks from prerigor beef longissimus (lumborum and thoracis) were prepared, placed in MAP, irradiated with 2 kGy, and stored at 15°C or 30°C. Postrigor longissimus steaks from the other half of each carcass were vacuum-packaged and stored at 2°C. Analysis for tenderness, lipid oxidation, color, and microbial growth were conducted over 2 wk. Aging irradiated prerigor beef at 30°C for 2 days with MAP resulted in similar Warner-Bratzler shear values as conventional wet aging at 2°C for 7 or 14 days, and steaks did not show discoloration, lipid oxidation, or microbial spoilage.     

宰后成熟过程中冷却牛肉、猪肉色泽和嫩度的变化

本实验比较研究了冷却牛肉和猪肉在宰后120h内色泽和剪切力的变化.分别从牛屠宰厂和猪屠宰厂选取牛、猪各4头,按规范工艺屠宰后取背最长肌,分切成8个肉块,经简易包装后在0～4℃下18、48、96、120h,之后测定肉色、剪切力值及其他相关指标.结果表明,牛肉和猪肉的pH值、肉色(L*、a*、b*)、水分含量、剪切力值等指标存在显著差异(p<0.05).随着成熟时间延长,亮度增加、红度下降、剪切力下降;宰后120h内,猪肉嫩度的变化比牛肉更明显.     

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.     

新疆褐牛不同部位牛肉在成熟过程中的品质变化

为研究新疆褐牛不同肌纤维类型组成的不同部位牛肉在成熟中品质变化,选取其具有代表性的冈上肌(SU)、冈下肌(IF)、臂三头肌(TB)、腰大肌(PM)、背最长肌(LD)、半腱肌(ST)、半膜肌(SM)和股二头肌(BF)八个部位肉,测定并分析成熟过程中(1、6和12 h以及1、3、7和14 d)的品质指标(色差、质构特性指标、剪切力、压力失水率、蒸煮损失、pH)变化。结果表明,该品种牛半腱肌具有最高的L^*值,腰大肌具有最高的a^*值。八个部位肉的硬度和弹性均随着成熟时间先增加后降低,且腰大肌的硬度低于其他部位。八个部位肉的剪切力随着成熟时间先增加后降低,腰大肌剪切力低于其他部位肉。股二头肌的剪切力变化率最大,半腱肌的剪切力变化率低于其他部位肉。腰大肌系水力较差,半膜肌的系水力较好。八个部位肉宰后成熟过程中蒸煮损失总体均呈增加的趋势。八个部位肉的pH的变化均是先降低后增加。本文为新疆褐牛精细成熟提供一定数据支持。     

不同注射处理对牛肉剪切力和肌原纤维小片化指数的影响

本文研究了不同注射处理对牛肉在成熟过程中剪切力,肌原纤维小片化指数(MFI)的影响。3头改良黄牛(鲁西黄牛×犁木赞)在屠宰厂按照标准的屠宰工艺屠宰并预冷20h后取样,将样品给予7个不同的处理,每个处理分别按样品重10%注射蒸馏水(作为对照)、200mmol/L CaCl2、200mmol/L EGTA、200mmool/L ZnCl2、0.2mg/ml亮肽素、0.2mg/ml亮肽素 1%Triton X-100、1%Triton X-100,处理后将样品分别成熟3、8、16d后测一些指标变化。结果发现注射外源性钙激活酶抑制剂(亮肽素,ZnCl2)显著降低了牛肉的成熟速度,使牛肉剪切力增加,MFI降低;而注射CaCl2则相反,且注射CaCl2后牛肉成熟4d时的剪切力和对照组成熟16d时的差异不显著(p>0.05)。     

Effect of High Pressure during heat Treatment on the Wamer-Bratzler Shear Force Values of Selected Beef Muscles

The effect on the Warner-Bratzler shear values of post-rigor beef muscles of heat treatments ranging from 40 to 80°C with or without concurrent pressure treatment at 150 MPa have been investigated. For muscles in a stretched condition, a decrease in shear values attributed to changes in the connective tissue was found to occur at a higher temperature in the pressure treated samples than in those not pressure treated. For muscles in a contracted condition, a steep increase in shear values with increase in cooking temperature (attributed to myofibrillar toughening) was prevented by pressure treatment. Instead, a decrease in shear values attributed to changes in connective tissue as found in stretched muscle, was then evident.     

Dynamical Changes of Beef Intramuscular Connective Tissue and Muscle Fiber during Heating and their Effects on Beef Shear Force

Changes of meat shear force and its characteristics during cooking have been extensively studied, but great variability existed due to the cooking method among different studies. This study was designed to focus on the dynamic changes of beef intramuscular connective tissue (IMCT) and muscle fiber during water-bath heating and their effects on beef shear force. At 4 d postmortem, beef semitendinosus muscles were divided into 11 steaks and then cooked respectively to an internal temperature of 40, 50, 55, 60, 65, 70, 75, 80, 85, and 90°C (the remainder was not cooked as control). Collagen content and its solubility, transition temperature of perimysia and endomysia, fiber diameter, and Warner–Bratzler shear force values (WBSF) were determined. The results showed that fiber diameter decreased gradually during cooking, concomitant with the increases in filtering residue and WBSF. The maximum transition temperature (T _max) of endomysial components was lower than that of perimysial components (50.2 vs. 65.2°C). Muscle fiber and IMCT (especially perimysia) shrank during cooking, resulting in the increase of WBSF when the internal temperature was lower than 75°C, but further cooking led to the disintegration of perimysial structure, lowing up the increase of WBSF between 75 and 90°C. For beef semitendinosus muscle, the internal temperature of 65°C is a critical cooking point where meat gets tougher.     

Relationship Between Weakening of Z-disks and Liberation of Phospholipids During Postmortem Aging of Pork and Beef

ABSTRACT: The liberation of phospholipids from Z‐disks was investigated to elucidate the cause of the structural weakening of Z‐disks, which contributes to the tenderization of meat during postmortem aging. The amounts of lipids in Z‐disks were 2.2 g per 100 g of myofibrillar proteins in porcine and 2.7 g in bovine semitendinosus muscles. Phospholipids were the major component of the lipids. The postmortem liberation of phospholipids correlated well with Z‐disk weakening, though a‐actinin, the major protein of Z‐disks, remained unchanged even after prolonged aging of pork and beef. We therefore concluded that Z‐disks are weakened by liberation of phospholipids during postmortem aging of pork and beef.     

AMPK活性对宰后牛肉糖酵解、肌肉内环境及品质的影响

为探究牛肉宰后成熟过程中单磷酸腺苷活化蛋白激酶（adenosine monophosphate-activated protein kinase,AMPK）对糖酵解、肌肉内环境及品质的影响,以0.50 mol/L 5-氨基咪唑-4-甲酰胺核苷（5-amino-4-imidazolecarboxamide,AICAR）处理的西杂牛背最长肌为对象,于4 ℃进行成熟,测定宰后成熟期间肌肉AMPKα基因（PRKAA1、PRKAA2）转录量、P-AMPK表达量、AMPK活性、糖酵解水平及品质指标的变化情况。结果表明：宰后24～120?h,处理组AMPKα基因转录量、P-AMPK表达量及AMPK活力均显著高于对照组（P＜0.05）;72～168?h,处理组pH值和肌糖原含量显著低于对照组（P＜0.05）,乳酸含量显著高于对照组（P＜0.05）;12～168?h,处理组L*、b*值及ATP、ADP、AMP和IMP含量均显著高于对照组（P＜0.05）,a*值显著低于对照组（P＜0.05）;24～120?h,处理组蒸煮损失率和肌原纤维小片化指数显著高于对照组（P＜0.05）,剪切力显著低于对照组（P＜0.05）。AICAR通过激活AMPK并加快宰后糖酵解影响肌肉内环境、肉色、剪切力及肌纤维微观结构变化,加快宰后肌肉成熟进程,说明AMPK活性对宰后肌肉糖酵解及品质变化具有重要影响,且可通过调控宰后肌肉AMPK活性来调节肌肉品质。