牛半腱肌肉结缔组织胶原蛋白热力特性热诱导变化DSC分析

探讨牛半腱肌肉结缔组织胶原蛋白热力特性的热诱导变化。牛半腱肌肉分别采用水浴和微波加热到内部终点温度分别为40、50、60、70、80℃ 和 90℃,研究结缔组织滤渣和热力特性在热处理过程中的变化。结果表明：结缔组织滤渣含量随着热处理温度的升高而增加,当加热温度分别为60、70℃ 和 80℃时,结缔组织滤渣含量在两种热处理方式间存在显著差异(P＜0.05)。在两种热处理方式中,40℃至60℃的内部终点温度是影响结缔组织胶原蛋白热收缩温度的关键加热温度。热诱导的结缔组织胶原蛋白热力特性的变化是水浴和微波加热牛肉胶原蛋白热收缩温度存在差异的主要原因。     

三种弱有机酸结合NaCl腌制对牛肉肌束膜和肌内膜胶原蛋白热力学特性影响

探讨三种弱有机酸(乳酸、醋酸和柠檬酸)结合NaCl腌制处理对牛肉肌束膜和肌内膜胶原蛋白热力学特性影响。牛半腱肌肉于4℃条件下分别经1.5%弱有机酸并与2%NaCl结合浸泡腌制24h,用差示扫描量热法研究肌束膜和肌内膜胶原蛋白热力特性(起始、最高和最终热收缩温度)在腌制处理过程中的变化。结果表明:3种弱有机酸的单独腌制处理后牛肉肌束膜胶原蛋白含量要比与NaCl的结合腌制处理低。不同腌制处理组之间,牛肉肌内膜胶原蛋白含量都有不同程度的差异。牛肉经腌制处理增强了肌内膜胶原蛋白的稳定性和部分处理组牛肉肌束膜胶原蛋白的热稳定性。     

饲养方式和屠宰季节对乌珠穆沁羊肉肌内结缔组织特性的影响

饲养方式和屠宰季节对肌肉结缔组织特性影响较大,以不同饲养方式和屠宰季节的乌珠穆沁羊半腱肌和背最长肌结缔组织、肌内膜和肌束膜为研究对象,利用分光光度法测定其胶原蛋白含量及热溶解性,分别利用高效液相色谱仪和差示扫描量热仪测定吡啶诺林的含量和热变性温度。结果表明：饲养方式对乌珠穆沁羊背最长肌结缔组织、肌内膜和肌束膜的胶原蛋白含量影响显著（P＜0.05）;屠宰季节对自然放养乌珠穆沁羊背最长肌结缔组织、肌内膜的胶原蛋白含量影响显著（P＜0.05）;半腱肌结缔组织和肌内膜的胶原蛋白含量均受饲养方式和屠宰季节的显著影响（P＜0.05）;饲养条件和屠宰季节对乌珠穆沁羊背最长肌结缔组织、肌内膜中可溶解胶原蛋白和半腱肌和背最长肌结缔组织中吡啶诺林含量均影响显著（P＜0.05）;吡啶诺林含量越高的样品可溶解性胶原蛋白含量越低;半腱肌结缔组织、肌内膜和肌束膜的热变性温度低于背最长肌,相同屠宰季节时,自然放养乌珠穆沁羊肉的热变性温度高于圈养。     

不同热处理方式和温度对牛半腱肌肉品质的影响

探讨不同热处理方式和温度对牛半腱肌肉品质的影响。牛半腱肌肉分别采用水浴和微波加热到内部终点温度分别为40、50、60、70、80℃ 和 90℃,研究牛肉品质特性在热处理过程中的变化。结果表明：在水浴加热中,牛肉剪切力随着热处理温度的升高而增加,而在微波加热过程中呈无规则变化。当加热温度为50℃ 和 90℃时,剪切力值在两种热处理方式间存在显著差异(P＜0.05)。随着加热温度的升高,牛肉微观组织结构发生显著的变化,主要表现为结缔组织和胶原蛋白出现变性和收缩现象,肌纤维收缩导致纤维直径减小。不同热处理方式和温度对牛肉品质有显著的影响。     

不同中心温度对牛肉胶原蛋白特性及嫩度的影响

本研究通过水浴加热牛肉使其达到不同的中心温度来探究胶原蛋白特性对嫩度及质构特性的影响,为煮制牛肉嫩度特性提供理论基础。将牛半腱肌肉在100℃水浴下加热至中心温度60℃、70℃、80℃、90℃、和100℃,通过测定其剪切力、蒸煮损失、水分含量、质构特性、胶原蛋白含量及热溶解性、共价交联以及扫描电镜等指标来探究嫩度的变化机制,最后通过相关性分析得出影响嫩度的关键因素。结果表明,随着中心温度的升高,牛半腱肌剪切力、胶原蛋白的含量及其热溶解性、羟赖氨酸吡啶啉、硬度、弹性、黏着性与咀嚼性增加;赖氨酸吡啶啉、凝聚性、胶黏性和回弹性下降。胶原蛋白含量以及可溶性胶原蛋白的溶解变性很大程度上影响了牛肉的嫩度,肉的弹性和咀嚼性与胶原蛋白含量以及共价交联有关,牛肉硬度下降与肌束膜肌内膜的完整性遭到破坏有关。     

不同加热条件对羊肉嫩度的影响研究

以羊半腱肌为原料,通过比较干热与湿热2种加热处理方式、4种加热过程(水浴、蒸煮、微波、烘烤)、不同加热终点温度(50℃~90℃)为研究目标,以蒸煮损失、p H、胶原蛋白溶解性、剪切力、质构特性分析为评价指标,阐述不同加热条件下羊肉肌内胶原蛋白特性的变化及其对肉样嫩度的影响机制。研究结果表明,(70~80)℃是影响羊肉质构特性的关键加热温度,在此温度范围内,肉样胶原蛋白的含量随温度升高而不断递增(P0.05),干热条件下的微波与烘烤加热处理后肌肉胶原蛋白含量显著高于湿热条件下的水浴与蒸煮加热处理(P0.05);湿热加热过程中,羊半腱肌蒸煮损失与剪切力都随着加热终点温度的升高呈现增加的趋势,但干热处理后的肉样剪切力在这一温度范围内呈逐渐减小的趋势。该研究探究和阐明了不同加热条件对羊半腱肌嫩度的影响,从而为羊肉生产和加工提供理论指导。     

乌珠穆沁羊生长过程中肌内结缔组织特性研究

以1～18 月龄乌珠穆沁羊为研究对象,分别利用羟脯氨酸法和DSC 法研究其生长过程中肌内结缔组织中胶原蛋白含量、胶原蛋白热溶解性及其热变性的变化。结果表明：结缔组织、肌内膜和肌束膜中胶原蛋白含量和热溶解性随着月龄的增加而显著下降(P ＜ 0.05),而且肌内膜中胶原蛋白含量和热溶解性明显高于肌束膜。结缔组织和肌内膜胶原蛋白的热变性温度随着月龄的增加而逐渐升高,肌束膜胶原蛋白的热变性温度随着月龄的增加而呈现下降趋势。     

不同地区羊肉肌内结缔组织特性的分析

采用了冬夏季蒙古羊-自然,乌珠穆沁羊-自然和乌珠穆沁羊-圈养羊的半腱肌和肱三头肌为研究对象,利用分光光度法测定样品结缔组织中的胶原蛋白的含量及其热溶解性。结果表明:3个品种羊不同季节屠宰后其半腱肌和肱三头肌中结缔组织的胶原蛋白含量最高,肌内膜胶原蛋白含量明显高于肌束膜中胶原蛋白含量。其中,半腱肌中的结缔组织的胶原蛋白含量分别均呈现显著下降趋势(p0.05),但是同一种羊冬、夏两季间半腱肌中的结缔组织的胶原蛋白含量变化不显著,同一季节屠宰的3个品种羊半腱肌的结缔组织、肌内膜、肌束膜中胶原蛋白含量均呈现显著差异(p0.05)。肱三头肌的结缔组织、肌内膜中胶原蛋白含量均呈现显著差异(p0.05),夏季乌珠穆沁羊-自然与圈养的肱三头肌中胶原蛋白含量变化不显著。3个品种羊不同季节的羊半腱肌和肱三头肌结缔组织内胶原蛋白热溶解性存在显著差异(p0.05),夏季半腱肌结缔组织内胶原蛋白热溶解性高于冬季半腱肌,冬季肱三头肌结缔组织内胶原蛋白热溶解性明显高于夏季。蒙古羊-自然的结缔组织内胶原蛋白热溶解性明显高于乌珠穆沁羊。     

水浴加热对牛半腱肌冷藏形成彩虹色斑的影响

研究水浴加热对牛半腱肌冷藏条件下形成彩虹色斑的影响。以新鲜牛半腱肌为实验材料,对其进行水浴(97℃)加热处理,使中心温度分别为70、80、90℃,在4℃条件下冷藏0～5 d,研究彩虹色斑强度、非血红素铁含量、蛋白质与脂质氧化、色泽等相关指标的变化,探讨水浴加热对牛半腱肌冷藏形成彩虹色斑的影响。结果表明,随水浴加热温度的升高和冷藏时间的延长,牛半腱肌彩虹色斑强度不断增强,其中亮度值(L*)和黄度值(b*)总体略有升高,而红度值(a*)略有降低,均出现显著差异(P<0.05);冷藏期间,牛半腱肌的非血红素铁含量、硫代巴比妥酸反应物(thiobarbituric acid reactive substance,TBARs)值、羰基含量显著升高(P<0.05),游离巯基含量显著降低(P<0.05);通过相关性分析得知,牛半腱肌彩虹色斑强度与非血红素铁含量、羰基含量、TBARs值呈显著正相关(P<0.05),与游离巯基含量呈显著负相关(P<0.05),与a*呈极显著负相关(P<0.01),可能是由于较高的非血红素铁含量促进TBARs值在冷藏0～1 d时迅速上升,同时促进蛋白质氧化进程,蛋白质与脂肪氧化过程同时发生,相互促进,从而共同影响彩虹色斑的形成。     

3种弱有机酸结合NaCl腌制对牛肉结缔组织滤渣胶原蛋白特性的影响

探讨3种弱有机酸(乳酸、醋酸和柠檬酸)结合NaCl腌制处理对牛肉结缔组织滤渣胶原蛋白特性影响。牛半腱肌肉于4℃条件下分别经1.5%弱有机酸并与2%NaCl结合浸泡腌制24h,研究结缔组织滤渣胶原蛋白提取率和SDS-PAGE变化以及用差示扫描量热法研究其热力特性(起始、最高和最终热收缩温度)在腌制处理过程中的变化。结果表明:3种弱有机酸的单独腌制处理后牛肉结缔组织滤渣胶原蛋白含量要比与NaCl的结合腌制处理低。不同腌制处理对牛肉结缔组织滤渣胶原蛋白不同分子量蛋白浓度的影响不显著。牛肉经腌制处理增强了结缔组织滤渣胶原蛋白的热稳定性。     

Changes in intramuscular connective tissue and collagen solubility of bovine m.semitendinosus during retorting

Vacuum-packed slices of bovine m.semitendinosus (ST) muscle were retorted to internal temperatures of 50, 60, 70, 80, 90, 100 and 121°C. Changes in the microstructure of the endomysium and perimysium were evaluated using a scanning electron microscope (SEM). Changes in solubility of intramuscular collagen were also estimated. In samples heated to 50°C changes in intramuscular connective tissue were not seen. At 60°C granulation of the perimysium and sarcolemma was seen, and on longitudinal sections, as well as granulation, fibrous structures of perimysium were observed. At 70°C increased granulation was observed. In the range 80-121°C progressive compression of the meat structure was seen in the transverse sections. The percentage of soluble collagen in the meat changed little up to an internal temperature of 60°C, but at 70°C it almost doubled, and in the range 80-121°C drastically decreased.     

Structural changes in endomysium and perimysium during post-mortem aging of chicken Semitendinosus muscle-Contribution of structural weakening of intramuscular connective tissue to meat tenderization

Post-mortem changes in endomysium and perimysium were investigated during aging of chicken semitendinosus muscle at 4°C. Although the shear-force value of raw meat decreased rapidly within 5 h post mortem and gradually thereafter, the solubility of collagen and the ratio of each chain of soluble collagen remained unchanged during 24 h post mortem. Light microscopic studies showed that structures of endomysium and perimysium disintegrated into several thin sheets within 12 h post mortem, and that many gaps opened in the cross-section of endomysium and perimysium. While endomysium and perimysium were not stained by periodic acid Schiff reagent in fresh muscle, they were markedly stained in muscle 12 h post mortem. These results provide direct evidence for the structural weakening of endomysium and perimysium during post-mortem aging of chicken. Therefore, we conclude that the structural weakening of the intramuscular connective tissue is closely related to tenderization of chicken.     

Effect of heating rate on shortening, ultrastructure, and fracture behavior of prerigor beef muscle

Rapidly heated prerigor beef is tender because of incompletely described myofibrillar disruption and tissue fracture. This study was designed to evaluate the effects of heating rate on heat-induced myofibrillar shortening, ultrastructural changes, and fracture behavior in prerigor triceps brachii muscle. Rapid heating (2°C/2 min) to 53°C caused (P < 0·05) more severe myofibrillar shortening in a shorter time and at higher muscle pH and temperature, less muscle weight loss, and shorter sarcomeres than slow heating (2°C/12 min) to 47 or 53°C. Rapid heating caused more extensive degradation of A and I bands, greater loss of the tridimensional pattern of myofibrils, more fragmentation and melting of myofibrils, widened intermyofibrillar spaces, and maximum separation of fiber bundles as compared to slow heating. Slow heating caused extensive shortening but not extensive degradation and disruption of myofibrils. Muscles slowly heated to 53°C sustained greater loss of structural integrity than those slowly heated to 47°C, but fracture behavior was similar. Separation and fracture occurred near the perimysial/endomysial junction in all heated samples, but the perimysium remained affixed to the endomysium at one side of the interface in many rapidly heated samples. Longitudinal fractures showed a granular endomysium and large numbers of supercontraction nodes alternating with areas of sarcolemmal membrane fragmentation and fiber tearing in rapidly heated samples. Alterations of myofibrillar ultrastructure and fiber structure, and separation of bundles, may account for enhanced tenderness of rapidly heated prerigor muscle.     

HEAT-INDUCED CHANGES IN EXTRACTABILITY OF BEEF MUSCLE COLLAGEN

Alterations in the extractability of collagen due to heating of beef muscle were determined and compared with shear and penetrometer values. Strips were heated in a water bath programmed to reproduce the internal temperature curve of a roast in a 163°C oven. Samples were removed at internal temperatures of 58, 67, 75 and 82° C. Data were collected on weight of raw and heated meat, amount of juice expressed during heating, moisture, fat and nitrogen content of the meat and juice, total and extractable collagen, and shear force and depth of penetrometer penetration. Solubilized collagen in the heated meat was determined by extraction with water at 40°C. The amount of soluble collagen increased with increasing internal temperature. Comparison of the solubilized collagen data with shear and penetrometer readings suggested that the changes in the contractile fibers influenced texture more than did the changes in the collagen of these muscles under these heating conditions.     

Textural Characteristics of Beef: Effects of the Heating System

Textural characteristics of beef semitendinosus roasts heated in 93 and 149°C ovens to 60 and 70°C were compared with those of small samples of semitendinosus heated as cylindrical cores in glass tubes in a water bath. The small samples were heated to the same endpoint temperatures as the roasts were at rates comparable to heating at the two oven temperatures. Cooking losses varied with heating method and in some cases with endpoint temperature and rate of heating. Heating method did not affect the textural parameters of penetration hardness, cohesiveness, and chewiness and shear cohesiveness and firmness. Hydroxyproline solubilization was greater in water bath samples than in intact samples heated at the slower rate. The extent of heat-related changes and their effects on final meat quality partially is determined by the heating system.     

Structural weakening of intramuscular connective tissue during post mortem ageing of chicken Semitendinosus muscle

The structural changes in intramuscular connective tissues endomysium and perimysium during post mortem ageing in chicken semitendinosus muscle were investigated using an improved technique of scanning electron microscopy. In post mortem chicken aged for 12 h at 4°C, the endomysium resolved into individual collagen fibrils and the perimysial sheets separated into collagen fibres. These results provide direct evidence for the structural weakening of endomysium and perimysium during post mortem ageing. The structural changes in the intramuscular connective tissue were minimal until 6 h post mortem, but clearly observable after 12 h post mortem. It was concluded that this disintegration of the intramuscular connective tissue is the chief mechanism in tenderisation during extended post mortem ageing of chicken.     

Relationship between degradation of proteoglycans and weakening of the intramuscular connective tissue during post-mortem ageing of beef

Changes in proteoglycans (PGs) during post-mortem ageing of bovine m. semitendinosus were studied. Electron microscopic observations made it clear that there were two types of PGs in bovine m. semitendinosus immediately post-mortem: PGs were arranged regularly in the basement membrane and PGs associated with collagen fibrils in the perimysium. After 28 days ageing at 4 °C, no PG was observed in the basement membrane, and the greater part of PGs in the perimysium had disappeared. The total amount of PGs decreased with time post-mortem. SDS-polyacrylamide gel electrophoresis indicated that PGs with a high molecular weight disappeared within 7 days post mortem. These results suggest that PGs are degraded during post-mortem ageing of beef. The degradation of PGs seems likely to be the main factor in the weakening of intramuscular connective tissues, i.e., separation of collagen fibrils and fibres from the endomysium and the perimysium, which results in the partial tenderization of beef during post-mortem ageing.