原子力显徽镜在牛肉嫩度测定中的应用研究

【目的】探讨原子力显微镜在牛肉嫩度测定中的应用,为肉品嫩度提供可靠、直观的测定方法。【方法】用100、150、200mmol/L不同浓度氯化钙(CaCl2)处理牛肉,肉样真空包装后于4℃下成熟72h后测定剪切力、肌原纤维指数(MFI),并用原子力显微镜观察肌原纤维小片,比较三者结果。【结果】三种测定方法结果基本一致,但有一定差异,原子力显微镜观察肌原纤维小片直观地反映了肌原纤维小片化程度。【结论】原子力显微镜能直观地反映肉的嫩化情况,是对剪切力和MFI测定方法在形态学上的完善。     

不同年龄牦牛宰后钙激活酶活性及嫩度指标变化

本研究对不同年龄牦牛宰后成熟过程中钙激活酶活性和嫩度指标（肌纤维直径、肌原纤维小片化指数（myofibrillar fragmentation index,MFI）、肌原纤维超微结构）进行测定。结果表明：成熟过程中,不同年龄牦牛肉肌纤维直径、MFI都发生显著变化（P＜0.05）,肌原纤维在成熟过程中Z线断裂,框架结构被完全破坏;钙激活酶活性在宰后的前2 d均显著下降（P＜0.05）,且成熟过程中不同年龄公牦牛的钙激活酶活性均高于母牦牛;成熟时间与钙激活酶活性、嫩度指标均成极显著相关性（P＜0.01）;牦牛宰后经过7 d的成熟,可以降低牦牛因屠宰年龄不同而产生的差异,同时也可以改善肉的嫩度;与公牦牛相比母牦牛宰后成熟时间可以适当的延长。     

不同处理对新疆羊半腱肌嫩度的影响

目的:寻求一种成本低、安全健康、嫩化效果好的嫩化方法。方法:以剪切力、pH值、蒸煮损失、肌原纤维小片化指数(myofibrillar fraglllentation index,MFI)、胶原蛋白含量及其溶解度、羊半腱肌全骨架蛋白降解情况等为评价指标,研究腌制结合滚揉、真空滚揉及腌制结合真空滚揉对羊肉嫩度的影响。结果表明:3种处理对羊肉的剪切力、pH值、蒸煮损失、肌原纤维小片化指数均影响显著。结论:采用真空滚揉对羊肉嫩化效果最佳。     

低压电刺激对不同部位宰后牦牛肉肌原纤维蛋白水解的影响

研究电刺激对不同部位牦牛肉宰后成熟过程中微观结构及肌原纤维蛋白水解的影响。将牦牛宰后5min内进行低压电刺激(21V,50Hz,90s)并冷却排酸,于宰后0、1、3、5d取前部肱三头肌(TB)中部背最长肌(ML)和后部半膜肌(SM),分析其肌节长度、肌纤维直径、MFI指数、肌原纤维超微结构和全肌肉蛋白电泳图谱。结果表明:电刺激使不同部位牦牛肉肌节长度显著变化(p0.05),肌纤维直径平均缩小6%、5%和9%;TB、ML和SM宰后0~5d MFI值分别上升54%、55%和92%,SM嫩度显著增大(p0.01);不同部位牦牛肉肌原纤维超微结构中挛缩带占有率分别为23.9%、26.3%和31.2%,肌原纤维结构形变溶解;SDS-PAGE电泳图谱显示,TB、ML和SM部肌原纤维蛋白均在48~75ku之间降解彻底。本研究证实了电刺激缩短牦牛肉宰后成熟时间,对不同部位牦牛肉嫩度改善,特别是对肉质较差的SM效果显著。     

宰后鹅肉成熟过程中品质特性变化的研究

通过对新疆伊犁鹅宰后成熟过程中肌肉品质特性变化的研究,意在阐明成熟对鹅肌肉嫩度的影响,为改善鹅肉制品加工过程中的嫩度提供依据。分别测定宰后4℃成熟期(1、3、5、7、10、14 d)鹅胸肌和腿肌的pH值、剪切力、系水力、肌原纤维小片化(myofibrillar fragmentation index,MFI)、色差值(L~*、a~*、b~*)以及超微结构分析,并进行了MFI值、pH值、系水力和剪切力的相关性分析。结果显示:鹅肉宰后pH值先下降后上升,鹅胸肌和腿肌在第3天时达到了极限p H值,而这段时间剪切力值和系水力值都很低。MFI在第5天后显著上升。色差L~*值先下降后升高,a~*值和b~*值总体逐渐下降。5天以后肌原纤维降解明显,Z线断裂,细胞器溶解。新疆鹅在宰后第4天～第5天成熟期内嫩度显著提高,适宜于加工食用,能够改善新疆鹅肉自身口感较粗的现象,可以为鹅肉制品的加工时间长,不易软烂问题提供解决方案。     

可溶性胶原蛋白含量、MFI、CAF与牛肉嫩化的关系

宰后向牛的股二头肌注射CaCl2和木瓜蛋白酶(Papain)来嫩化牛肉,并于后熟24h左右进行了肌原纤维小片化指数(MFI)、粗钙激活因子活性(CAF)和可溶性胶原蛋白含量等指标的测定。实验结果表明,这些指标对于衡量牛肉嫩度,具有良好的效果。     

不同质量等级延边黄牛肉肌纤维的组织特性

选取36月龄延边黄牛的眼肉作为肉样,对剪切力、肌纤维组织特性及各指标的相关性进行分析,结果表明:剪切力整体呈现下降趋势,成熟时间和质量等级对剪切力影响显著(P＜0.05).随成熟时间延长,肌纤维密度和肌原纤维小片化指数(MFI)增大,肌纤维直径和肌纤维面积减小,嫩度得到提高.成熟时间和质量等级对肌纤维组织特性影响显著(P＜0.05),各质量等级延边黄牛肉嫩度大小为:特级1+＞优一级＞优二级＞普通级,说明成熟对牛肉嫩度有所提高,质量等级越高牛肉嫩度越好.     

不同电刺激处理时间对宰后马肉成熟过程中嫩度的影响

采用不同电刺激处理时间对宰后马肉进行处理,对马肉成熟过程中的蒸煮损失率、剪切力、可溶性蛋白浓度(soluble protein concentration,SPC)、肌原纤维小片化指数(myofibrillar fragmentation index,MFI)、胶原蛋白溶解性及微观结构进行研究。结果表明:不同电刺激处理时间对宰后马肉成熟过程中的蒸煮损失率没有显著影响(P0.05);在一定电刺激处理时间范围内,马肉成熟过程中剪切力下降,SPC上升,MFI上升,胶原蛋白溶解性上升。实验条件下电刺激60 s对改善马肉的嫩度具有较好的效果,进一步延长电刺激处理时间对嫩度的改善效果不明显。电刺激60 s、成熟14 d时,马肉剪切力较对照组下降了13.8%,SPC与MFI分别是对照组的1.16倍与1.28倍,电刺激破坏了马肉的肌纤维结构。适当的电刺激处理能够促进宰后马肉的成熟,使较为粗糙的马肉得到有效的嫩化。本研究为马肉电刺激嫩化机理及产品开发提供了一定的理论依据。     

肌肉嫩化方法及其机理分析

嫩度是肌肉重要的食用肉品质特征之一,影响肌肉嫩度的因素多种多样,包括肌原纤维、胶原蛋白、内源酶在内的内部因素,和温度、pH值等外部因素。阐述了物理(电刺激、高压处理、超声波)、生物化学(盐类、有机酸和生物酶)处理技术以及多种嫩化方法结合技术改善肌肉嫩度的方法,分析了不同的嫩化机理,并就肌肉嫩化机理分析研究进行了展望。     

嫩化时间对大口黑鲈半成品品质的影响

为改善淡水鱼加工和灭菌过程导致的肉质老化和嫩度下降问题,以大口黑鲈(鲈鱼)为研究对象,通过物性测定、十二烷基磺酸钠-聚丙烯酰胺凝胶电泳和扫描电镜系统考察复合嫩化剂(氯化钙1.2‰、复合磷酸盐1.2‰、木瓜蛋白酶1.8‰,均为质量分数)作用时间对鲈鱼半成品的嫩化效果。结果表明:用该嫩化剂嫩化鲈鱼半成品1.0~1.5 h,可显著降低鱼肉剪切力和硬度分别至(21.89±0.27)N和(111.98±3.46)g,提高鱼肉pH值和L*,并增加鱼肉肌原纤维小片化指数;上述指标均和对照组差异显著(P0.05)。凝胶电泳结果显示,嫩化后鱼肉肌原纤维中分子质量38 kD的蛋白和原肌球蛋白发生降解,在约37 kD和28 kD处产生了新的蛋白条带。扫描电镜结果表明,嫩化后鱼肉组织变得蓬松、肌纤维间连接物消失、肌原纤维发生断裂。该复合嫩化剂效果良好,嫩化1.0~1.5 h可显著提升鱼肉半成品品质。     

Tenderization and fragmentation of myofibrillar proteins in bovine longissimus dorsi muscle using proteolytic extract from Sarcodon aspratus

The objective of this study was to examine the Sarcodon aspratus extract including protease how to affect tenderness of the bovine longissimus dorsi muscle. In addition, we investigated myofibrillar protein fragmentation, particularly in myosin, and its influence on meat tenderness. Beef loin chunks were marinated with 0.5 g/100 g, 1 g/100 g, and 2 g/100 g powdered S. aspratus extract, 0.2 g/100 mL papain, and distilled water (control), respectively. Although tenderness of meat is increased by adding S. aspratus extract, differences in meat quality traits, such as muscle pH and meat color, were small and not considered to have practical importance between the control and enzyme-treated samples. Furthermore, the S. aspratus extract influenced the myofibril fragmentation index (MFI) as well as protein solubility. The changes in MFI and protein solubility were due to the myofibrillar protein degradation. Through Western blotting, we found that the S. aspratus extract, as well as papain, caused fragmentation of the myosin heavy chain, but the mushroom extract induced more fragmentations of myofibrillar proteins, and caused more tender meat.     

Effect of very fast chilling and aging time on ultra-structure and meat quality characteristics of Chinese Yellow cattle M. Longissimus lumborum

Objectives of the current study were to evaluate meat ultra-structure and tenderness variation at different chilling regimes and aging times. Hot boned longissimus lumborum of 18 Chinese crossbred cattle were divided into 4 portions per side. One portion underwent very fast chilling (VFC, at -21°C to achieve core temperature of 0°C, then transferred to another incubator at 2°C), whereas other treatments were held at 14, 7 and 0°C for 10h postmortem, respectively. At 10h postmortem, all muscles were vacuum aged at 2°C for 21d. Cold shortened muscles had greatest absolute amount of tenderization during aging. VFC caused lowest sarcomere length, with super-contractions, ruptured Z-lines and myofibril cleavage, but improved myofibril fragmentation index (MFI), with no significant negative effect on toughness. Overall, aging improved the meat quality of cold shortened beef. Moreover, it should be prudent in some applications to apply VFC to excised muscles from a food safety perspective, and to improve tenderness compared to cold-shortened muscles.     

Aging of Frozen Parts of Beef

Due to religious regulations, the beef imported into Israel is frozen soon after boning. In a search for a method for optimal aging of the beef after thawing and koshering, 8 different aging experiments were conducted, from 0-12 days. Cooking loss and myofibril fragmentation index were found to be more affected by the freezing preceding aging. Nonprotein nitrogen components were found to increase during optimum aging and then decrease. Sensory evaluation of tenderness, performed by multiple-paired comparisons, indicated a significant improvement in meat tenderness after 1 day of aging and further gradual improvement up to 7 days.     

Meat tenderization by calcium chloride after osmotic dehydration

In this study, meat was tenderized by dipping the meat in a calcium-containing solution after osmotic dehydration. Dehydrated meats were dipped in a 150 mM calcium chloride solution for 3 h, and after that stored for 24, 48, and 168 h at 3 ～ 4°C. Then, meat was subjected to texture measurement, sensory evaluations, biochemical analysis and histological observations. A gradual decrease in the firmness and higher tenderness sensory scores were observed in the meat treated with calcium chloride as compared with the untreated meat. Few differences were observed in water holding capacity by treatment at any stage of storage. A gradual increase in the myofibril fragmentation from the calcium chloride-treated meats was observed throughout the storage compared with the controls. Broadening of the I band and a disordered Z-line were observed in the treated meat. The deformation of the honeycomb-like structure of the endomysium was also observed in the treated samples. Therefore, the dipping in 150 mM calcium chloride solution after dehydration can be applied to improve meat tenderness without detrimental effects on other palatability and quality traits.     

ULTRASTRUCTURAL CHANGES IN BOVINE LONGISSIMUS MUSCLE CAUSED BY THE HYDRODYNE PROCESS

Transmission electron microscopy was used to examine the influence of the Hydrodyne process, a new technology for tenderizing meat in the raw state, on the ultrastructural characteristics of bovine longissimus muscle. Myofibrillar fiagmentation in the region adjacent to the Z-lines was clearly evident. Fragments of Z-lines were attached to the A-band on both sides of the fractures. These fractures resulted in increased intrumyofibrillar spaces with longitudinal gaps or splits in the myofibril lattice (lattice of filaments formed inside the myofibril). These observations offer evidence as to why there is a significant improvement in meat tenderness when meat is treated with the Hydrodyne process.     

Biochemistry of postmortem muscle — Lessons on mechanisms of meat tenderization

It is certain that meat tenderness is a highly valued consumer trait and thus definition of the multiple processes that influence meat tenderness will provide clues toward improving meat quality and value. The natural process by which meat becomes tender is complex. Tenderness development is dependent on the architecture and the integrity of the skeletal muscle cell and on events that modify those proteins and their interaction. Specifically protein degradation and protein oxidation have been identified as processes that modify proteins as well as the tenderness of meat. The intracellular environment is a major factor that controls these events. Ultimately, the interplay between these events determines the rate and extent of tenderization. Given the intricacy of the structure of the muscle cell, coupled with the complexity of the regulation of protein modification and the ever-changing intracellular environment it is not surprising that this area of research is a very dynamic field. Just as the overall integrity and function of muscle cells does not depend on a single protein, but rather on the coordinated interaction of several proteins, the structural weakening of muscle cells during postmortem aging also must not depend on the degradation of a single myofibrillar or other cytoskeletal protein. The proteins mentioned in this review are located in different regions of the muscle cell, and most have been implicated in some manner as being important in maintaining the structure and function of the muscle cell. Oxidation of myosin heavy chain, a predominant protein in the myofibril, is known to promote aggregation and toughening of meat. Degradation of proteins such as desmin, filamin, dystrophin, and talin (all located at the periphery of the Z-line) may disrupt the lateral register and integrity of the myofibril themselves as well as the attachments of the peripheral layer of myofibril to the sarcolemma. Degradation of the proteins within the myofibril that are associated with the thick and thin filaments may allow lateral movement or breaks to occur within the sarcomeres of postmortem aged samples. Titin, nebulin, and troponin-T, by their ability to directly interact with, or modulate the interaction between, major proteins of the thick and thin filaments and (or) the Z-line, play key roles in muscle cell integrity. Disruption of these proteins, especially titin and nebulin, could initiate further physicochemical and structural changes that result in myofibril fragmentation and loss of muscle cell integrity, and ultimately in tenderization of the muscle. In order to make real progress in this area, the scientific community must have a global appreciation of how both the structural proteins and the key proteases are influenced by the vast changes that occur during the conversion of muscle to meat.     

肌球蛋白的解离研究进展

肌球蛋白是肌肉中含量最高的蛋白质，占肌原纤维总蛋白质的60%。肌球蛋白能提高肉制品的保水性和嫩度、增强脂肪乳化稳定性、改善凝胶肉制品品质，对肉制品的加工具有重要意义。然而，肌球蛋白通常被束缚在肌原纤维粗肌丝中，若要充分发挥其作用，需将其从肌原纤维中解离出来。该研究综述了肌动球蛋白的解离对加工肉制品品质的影响，并在此基础上进一步讨论了肌动球蛋白的解离机制，同时对加工过程中温度、pH值、食盐与焦磷酸盐等影响肌动球蛋白解离的因子进行研究和总结，为肉制品加工提供新思路，为提高加工肉制品品质奠定基础。     

Postmortem Calcium Chloride Injection Alters Ultrastructure and Improves Tenderness of Mature Chinese Yellow Cattle Longissimus Muscle

ABSTRACT: This study was conducted to test the hypothesis that postmortem calcium injection could activate the calpain system in mature Chinese Yellow Cattle muscle, thereby promoting meat tenderization through disruption of the myofibril structure during aging. A 10% (w/w) injection of CaCl₂ (300 m M ) solution lowered the Warner-Bratzler shear values of longissimus muscle by more than 30% ( P < 0.05), even with only 24 h postmortem storage when compared with noninjected or water-injected controls. The accelerated meat tenderization by the Ca²⁺ treatment paralleled the changes in myofibril fragmentation index and fracture of the myofibril ultrastructure throughout the sarcomere but most notably around the I-bands and the Z-disks. Injection of ZnCl₂ (50 m M ) largely inhibited these proteolytic changes. The colorimetric L * and a * values were not affected by CaCl₂ nor by ZnCl₂ injection. The results suggest that postmortem CaCl₂ injection can be used to help resolve the toughness problem of mature Chinese Yellow Cattle meat and shorten the aging time required to achieve adequate tenderness.