【作者】 李超；

【导师】 高峰； 徐为民；

【作者基本信息】 南京农业大学 ， 动物营养与饲料科学， 2012， 博士

【摘要】 肉的食用品质在很大程度上决定了消费者的购买趋向,继而影响生产者的生产趋向,嫩度被广泛认为是重要的食用品质。嫩度主要由肌原纤维和结缔组织两部分决定,前者构成了肉的肌动球蛋白硬度(Actomyosin toughness),后者构成了肉的基础硬度(background toughness)。肉在食用前通常要经过加热处理,在加热处理过程中,肉中蛋白质变性,引起肉结构的变化,最终对嫩度产生影响。本研究以鸭肉为原料,应用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、质构仪(TPA)以及SDS-PAGE研究了水浴加热过程中鸭肉嫩度的变化规律、肌原纤维和结缔组织的变化情况及其对嫩度的影响、肌动球蛋白的解离情况及其对嫩度的影响,并从肌动球蛋白解离入手探索嫩度的调控与改善,从而为鸭肉生产和加工提供理论指导。本研究分为四个部分,具体研究内容和结果如下：1、中心温度对鸭肉嫩度的影响及机制研究了鸭肉在100℃恒温水浴加热过程中,其嫩度随鸭肉中心温度升高而变化的动态过程,以及肌原纤维和结缔组织的变化及其对嫩度的影响。结果显示：随着鸭肉中心温度的升高,剪切力总体呈现出不断增加的趋势,同时伴随着蒸煮损失的不断增加,并且剪切力的增加分阶段：第一个阶段在50℃以下(P<0.01),第二阶段为60-95℃(P<0.01),并且50-60℃剪切力存在一个减小的过程。随着温度的增加,肌原纤维蛋白溶解度不断下降(P<0.01)。其中在70-80℃阶段下降最明显(P<0.01)。同时肌原纤维发生收缩,肌纤维直径不断减小(P<0.01),其中在40-50℃和70-80℃两个阶段肌纤维直径的收缩最剧烈(P<0.01)。肌节长度随温度的增加而减小(P<0.01)。在40-50℃和80-95℃,肌节长度极显著减小(P<0.01)。但在50-60℃,有一个增加的过程。随着温度升高,70℃以前胶原蛋白溶解度变化不明显(P>0.05),70-80℃,胶原蛋白溶解度显著增加(P<0.01),在80℃胶原蛋白溶解度达到最大值,但随着温度的升高,80-95℃,胶原蛋白溶解度迅速下降(P<0.01)同时肌束膜和肌内膜结构也不断受到破坏,出现颗粒化现象。相关分析表明剪切力与蒸煮损失、肌原纤维蛋白溶解度以及肌节长度均极显著相关(P<0.01),但与胶原蛋白溶解度、肌纤维直径的相关性不显著(P>0.05)。本实验结果表明,不同中心温度显著影响鸭肉嫩度,鸭肉嫩度呈现出阶段性变化的特点,肌原纤维的收缩对嫩度下降的两个阶段均有影响,结缔组织的变化对嫩度下降第一个阶段可能有影响,但在70℃以上,结缔组织结构的破坏、胶原蛋白的溶解起到改善嫩度的作用。2、保温时间对鸭肉嫩度的影响及机制研究了鸭肉在加热到不同温度(60、80、100℃)后,延长加热时间到10、30、60min对嫩度的影响,以及肌原纤维和结缔组织的变化及其对嫩度的影响。结果显示：随着保温时间的延长,在60℃,剪切力有下降的趋势,但差异不显著(P>0.05)；在80℃,剪切力变化不明显(P>0.05)；在100℃,剪切力极显著降低(P<0.01)。随着保温时间的延长,在60和80℃,蒸煮损失极显著增加(P<0.01),但80℃下蒸煮损失整体高于60℃；在100℃,蒸煮损失已经接近最大值,继续增加保温时间对蒸煮损失影响不明显(P>0.05)。增加温度和延长保温时间均可导致肌原纤维蛋白溶解度下降,肌原纤维收缩,使得鸭肉肌原纤维结构变得更加致密。在60℃,随着保温时间的延长,肌原纤维蛋白溶解度极显著下降(P<0.01),肌纤维直径有增加的趋势(P<0.05),肌节长度总体上也有增加的趋势(P<0.05)；在80和100℃,肌原纤维蛋白溶解度接近最低值,随着保温时间的延长,肌原纤维蛋白溶解度变化不明显(P>0.05),鸭肉肌纤维直径逐渐减小(P<0.01)。在80℃,随着保温时间的延长,肌节长度逐渐减小(P<0.01)；在100℃,随着保温时间的继续延长,肌节长度变化不明显(P>0.05),且肌节长度整体上小于80℃。相关分析表明,在不同保温时间下,剪切力与蒸煮损失、肌浆蛋白溶解度、肌纤维直径显著相关(P<0.05)。蒸煮损失与与肌纤维直径显著相关(P<0.05),与肌原纤维蛋白溶解度、肌浆蛋白溶解额度、胶原蛋白溶解度、肌节长度极显著相关(P<0.01)。本实验结果表明,延长保温时间嫩度有改善的趋势,肌原纤维蛋白溶解度有降低的趋势,而肌原纤维结构收缩,热溶性胶原蛋白有增加的趋势,肌内膜和肌束膜结构完整性受到破坏,逐渐颗粒化。肌原纤维和结缔组织联合作用的净效应决定了最终的嫩度。3、加热处理对鸭肉肌动球蛋白解离的影响研究了不同温度下,鸭肉肌动球蛋白的解离情况,并初步探索影响肌动球蛋白解离的因素。结果显示,在40℃,与对照组相比,上清液中肌动蛋白条带无明显变化；在50℃,加热10min后,肌动蛋白条带浓度明显增加,继续加热到60min,肌动蛋白条带浓度仍然明显高于对照组。在60℃,与50℃电泳结果类似,且加热时间从30-60min,肌动蛋白条带浓度有减弱的趋势；在70℃、80℃、100℃,没有肌动蛋白条带出现。从总体上看,肌动蛋白条带只在50-60℃加热处理的鸭肉中明显出现,而在50℃以下则基本没有变化,在70℃以上,也检测不到肌动蛋白条带的存在。在50-60℃加热条件下,肌动蛋白条带浓度显著高于对照组(P<0.05),但随着加热时间延长,肌动蛋白条带浓度有减弱的趋势。在4℃,鸭肉肌动球蛋白经8mM或16mM的AMP或IMP处理后,与对照相比肌动蛋白条带浓度均显著增加(P<0.05)；在60℃,与对照相比,经过16mM的AMP或IMP处理后,肌动蛋白条带浓度显著增加(P<0.05)。经8mMM或16mM的ATP处理后,无论在4℃或60℃,肌动蛋白条带浓度显著低于对照(P<0.05)。本实验结果表明,加热过程中,鸭肉肌动球蛋白在50-60℃显著解离,并且解离可能存在逆转,在更高温度下,肌动球蛋白可能不经解离即变性转为不溶状态,AMP和IMP对肌动球蛋白解离有促进作用。4、梯度加热对鸭肉嫩度的影响及与肌动球蛋白解离的关系研究了鸭肉在不同梯度加热条件下嫩度的变化,以及肌原纤维和结缔组织的变化及其对嫩度的影响。结果显示,与常规加热方法相比,在终点温度70℃,三段式加热处理显著降低了鸭肉剪切力(P<0.05),在终点温度80和90℃,三段式加热仍有降低剪切力的趋势,但差异不显著(P>0.05)；而两段式加热在终点温度70℃,有降低剪切力的趋势,但在终点温度80、90、95℃,两段式加热均显著增大了鸭肉剪切力(P<0.01)。与常规加热方法相比,三段式加热的鸭肉在各个终点温度下的亮度值、红度值、黄度值均差异不显著(P>0.05)；两段式加热的鸭肉在各个终点温度下的亮度值均有极显著降低(P<0.01),红度值均有极显著升高(P<0.01),黄度值变化不明显(P>0.05)。在终点温度70℃,与常规加热相比,三段式加热的肌节长度均极显著增大(P<0.01),肌纤维直径有减小的趋势,但差异不显著(P>0.05),而两段式加热下肌节长度有增大的趋势,但差异不显著(P>0.05),肌纤维直径则显著减小(P<0.05)；经过三段式加热的鸭肉肌束膜和肌内膜结构破坏程度更严重,颗粒化程度也增加；与常规加热方法相比,两段式加热方法在各个终点温度下胶原蛋白溶解十分接近,差异不显著(P>0.05),三段式加热方法在各个终点温度下胶原蛋白溶解度则有降低的趋势,但差异也不显著(P>0.05)。本实验结果表明,在终点温度70℃,与常规加热方式相比,梯度加热有降低鸭肉剪切力、改善嫩度的趋势,肌原纤维收缩受到保温时间抑制于此相关。尤其是三段式加热,对鸭肉嫩度有明显的改善作用同时对肉色和蒸煮损失无明显影响,相比常规加热而言,是一种较为理想的加热方式。综上所述：本研究中,不同中心温度和保温时间对鸭肉嫩度均有影响,对肌原纤维和结缔组织的蛋白溶解性、超微结构也有显著影响,肌原纤维和结缔组织两者变化的联合作用决定了鸭肉最终的嫩度情况,肌动球蛋白的解离与嫩度有一定的关联性,梯度加热通过促使肌动球蛋白解离和结缔组织结构破坏、胶原蛋白溶解起到改善鸭肉嫩度的作用。更多还原

【Abstract】 The eating quality of meat has a large effect to determine the trends of consumer consumption and the trends of producer’s production. The tenderness is affected mostly by the two main components namely myofibril and connective tissue, the former formed the actomyosin toughness, while the latter formed the background toughness. Meat normally undergoes heat treated before eating, during heat process, the meat protein denatured, causing structural changes of meat, and finally impact on tenderness. In this research, duck meat was used as material to study changes of duck meat tenderness during water bath cooking and changed in myofibril and connective tissue and their contributing to tenderness by SEM, TEM, TPA, SDS-PAGE, etc., the dissociation of acotomyosin and its relationship with tenderness is also investigated, in order to Provide theoretical guidance for duck production and processing. A total of four parts are including in this study, the details as follow:1change of duck meat tenderness with different final internal temperature and its mechanismsIn this study, the dynamic process of the duck meat cooking up to100℃, and changes in myofibril and connective tissue are investigated. The results showed that:with increasing internal temperature, the shear force value gradually increased, accompanied by increasing cooking loss. The change of shear force is found to increase in two stages. The first stage is below50℃(P<0.01), the second stage is60-95℃(P<0.01), and between50-60℃the shear force get a reduction process. With increasing temperature, the myofibrillar protein solubility decreased (P<0.01). the decrease was found most significant in70-80℃(P<0.01). in the meanwhile, the structure of myofibrillar contraction, shortening of muscle fiber diameter occurred (P<0.01), the most severe contraction in the muscle fiber diameter is40-50℃and70-80℃(P<0.01). sarcomere length signifiantly decreased (P<0.01),however with a temporary increase between50-60℃. Collagen solubility significantly increase after cooked to70℃(P<0.01)and reached the highest point at80℃, but decrease with higher temperature(P<0.01). Perimysium and endomysium structure continues to receive damage, the phenomenon of granulation occurred. Correlation analysis showed that the shear force significant correlated with cooking loss, myofibrillar protein solubility and sarcomere length are very (P<0.01), but not significant with solubility of collagen, muscle fiber diameter (P>0.05). The results suggested that internal temperature has a large impact on tenderness; change of tenderness is showed in increase in two stages. Changes in myofibril contribute to both stage of toughness; changes of connective tissue main contribute to the first stage of toughness, at temperature higher70℃, in contributes to improve tenderness.2changes of duck meat tenderness during different retention and its mechanismsThis study investigated the changes of tenderness, myofibril and connective tissue when duck meat was holding for different time (0,10,30,60min) at different temperatures. The results showed that:with increasing holding time, at60℃,the shear force has a downward trend(P>0.05); at80℃, there is no apparent changes in shear force value(P>0.05); at100℃, the shear force significantly decreased(P<0.01). with increasing holding time, at60and80℃, cooking loss significantly increased (P<0.01)at100℃, the cooking loss reached the highest point, and no apparent changes with holding time(P>0.05). With increasing temperate and holding time, the myofibrillar protein solubility decreased, cause shrinkage of myofibrils and thereby the structure. At60℃, the myofibrillar solubility significantly decreased(P<0.01), the fiber diameter increase in trend (P<0.05), sarcomere length also increased in trends(P<0.05); At80and100℃, the myofibrillar protein solubility reached its lowest point and showed non apparent change with holding time(P>0.05), the fiber diameter gradually decrease (P<0.01). At80℃, sarcomere length decreased with increasing time(P<0.01); At100℃, no apparent changes occur(P>0.05). The shear force is significantly correlated with cooking loss, sarcoplasmic protein solubility, sang fiber diameter (P<0.05). Cooking loss significant correlated with fiber diameter (P<0.05), and highly correlated with myofibrllar protein solubility, collagen solubility and sarcomere length (P<0.01). The results suggested that:with increasing holding time, the tenderness improved, myofibrillar protein solubility decreased in trends, collagen solubility increased in trends, structure of parimysium and endoumysium destroyed and granulated. Both myofibril and connective tissue affect the final meat tenderness.3the effects of heat treatment on dissociation of actomyosin of duck meatThis study determined the dissociation of actomyosin during cooking process, and explores the factor that affects dissociation. The results showed that at40℃, compared with the control group, the actin protein band had no significant change; at50℃for10min, the actin bond density significantly increased and still significantly higher than the control. At60℃, the results were similar with that at50℃, from30-60min, actin bond concentration decreased in trends; At70℃,80℃,100℃, no actin bond was found. In general, actin bond occurred mainly between50-60℃, it was no apparent changed in actin bond density below50℃, and no actin bond occurred higher than70℃. Quantity analysis of actin bond between50-60℃showed that, the actin bond density significantly higher compare to the control, with increasing time the actin bond density decreased in trends. At4℃, In actomyosin treated with8mM or16mMAMP or IMP, the actin bond density increased significantly compare to the control; At60℃, actin bond density in actomyosin treated with16mM AMP or IMP significant increased compare to the control. In actomyosin treated with8mM or16mM ATP, actin bond density significant lower compare to the control(P<0.05) at4℃and60℃. The results suggest that, dissociation of actomyosin mainly occurred between50-60℃, and the dissociation maybe reversed, at higher temperature, actomyosin seemed denaturized without dissociation. AMP and IMP could be contributing to dissociation of actomyosin.4The effect of staged cooking duck meat tenderness and its relations to dissociation of actomyosinThis study investigated the change of myofibril and connective tissue structure and its relationship with tenderness. The results showed that, at endpoint70℃, the three-stage cooking significantly lower shear force(P<0.05), at endpoint80and90℃, the shear force still decrease in trends(P>0.05); the two-staged cooking also decrease shear force in trends at endpoint70℃, but significant increase shear force at endpoint80、90、95℃(P<0.01). Compare to the convention cooking, the three-staged cooking have no apparent different in the light value, red value, and yellow value (P>0.05) at each endpoint temperature. The two-staged cooking significant lower the light value at each endpoint temperature (P<0.01), significant increase the red value (P<0.01), and no apparently changes in yellow value (P>0.05). at endpoint70℃, compare to convention cooking, the sarcomere length by the three-staged or two-staged cooking significant increased(P<0.01), the fiber diameter decreased in trends(P>0.05), and connective tissue by the three-staged cooking destroyed more severe; at each endpoint temperature, compare with convention cooking, the collagen solubility by two-staged cooking has no apparent deference(P>0.05), the three-staged cooking decreased collagen solubility intends, however, no statistical signifier was found (P>0.05). The results suggest that, at endpoint70℃, compare to convention cooking, the staged cooking could be improve tenderness of duck meat, this is found in relationship with the restrict of myofibril shrinkage. The three-staged cooking was a better cooking regime compare to convention cooking, as it improved tenderness without negatively affect meat color and cooking loss.Taken all the results in account, both the internal temperature and Holding time significant affect duck meat tenderness, and the myofibrillar and connective tissue structure, the net effect of the two components caused the final tenderness of duck meat. The staged cooking caused dissociation of actomyosin and destroys of connective tissue, increase collagen solubility; all these could improve duck meat tenderness.更多还原