改性甘蔗膳食纤维对猪肉肌原纤维蛋白凝胶特性的影响

The Mechanism of Myofibrillar Protein Gel Functionality Influenced by Modified Sugarcane Dietary Fiber

【目的】探究肌原纤维蛋白凝胶网络结构—膳食纤维-肌原纤维蛋白的填充结构—复合凝胶断裂应力应变三者之间的相互关系,阐释改性甘蔗膳食纤维对肌原纤维蛋白凝胶特性的作用机制,为甘蔗膳食纤维作为脂肪替代物在低脂营养香肠中的应用提供理论依据。【方法】本试验利用碱性过氧化氢法对甘蔗膳食纤维进行改善,以添加不同比例和粒径的膳食纤维——肌原纤维蛋白为模拟体系,其中未添加甘蔗膳食纤维的试验组为对照组;添加1.0%、2.0%和3.0%的50目甘蔗膳食纤维的试验组分别命名T150、T250和T350;添加1.0%、2.0%和3.0%的100目甘蔗膳食纤维的试验组分别命名T100、T200和T300。利用流变仪测定模拟体系的动态流变特性,利用质构仪测定复合蛋白的凝胶离心损失和断裂形变时应力应变,利用扫描电镜和图像分别分析肌原纤维蛋白凝胶网络微观结构及微观结构的分维维度和缺项值,通过石蜡切片观察膳食纤维在肌原纤维蛋白凝胶基质中的空间分布。【结果】复合蛋白凝胶的离心损失随着膳食纤维添加比例和粒径增大而显著降低。复合蛋白凝胶的储能模量(G')随着膳食纤维添加比例和粒径增大而显著提高。复合蛋白凝胶断裂形变时的应力应变结果显示,膳食纤维提高了复合凝胶断裂形变时的应力,而降低了应变。石蜡切片显示膳食纤维和肌原纤维蛋白属于热力不相溶体系,两者之间没有发生离子或共价交联,膳食纤维只是以简单的物理填充形式镶嵌在肌原纤维蛋白凝胶基质中,并形成大量大小和形状各异的空洞。扫描电镜显示未变性对照组的肌原纤维蛋白凝胶网络结构中布满了相互交错的水沟壑,这些沟壑的存在严重阻碍蛋白疏水基团之间的交联,进而导致肌原纤维蛋白凝胶网络结构比较疏松;膳食纤维能够减少蛋白三维网络结构中相互交错的水沟壑,肌原纤维蛋白凝胶网络结构更加致密均一。图像处理软件分析结果显示,添加3.0%50目甘蔗膳食纤维的肌原纤维蛋白凝胶网络结构的分维维度(1.8670)最高(P<0.05),而缺项值(0.19)最低(P<0.05)。【结论】甘蔗膳食纤维-肌原纤维蛋白复合凝胶体系是以热诱导凝胶蛋白网络结构为骨架结构,以甘蔗膳食纤维作为填充相、蛋白基质为连续相形成的填充复合物。从骨架结构角度,甘蔗膳食纤维的物化特性显示其粒径大小与持水力成正比,添加3%50目甘蔗膳食纤维能够完全消除蛋白基质中的水壑并促进蛋白交联从而形成致密的凝胶网络结构,具有最高断裂形变时的应力。从填充结构角度看,50目甘蔗膳食纤维的体积巨大,在蛋白基质中会形成体积较大的空穴,其非弹性属性导致复合蛋白凝胶断裂形变时的应变显著降低。因此,添加100目甘蔗膳食纤维作为脂肪替代物能够显著提高复合蛋白凝胶的断裂应力,同时极大限度的保持复合蛋白凝胶的弹性。

【Objective】The relationships between the myofibrillar protein gel networks,the spatial distribution of dietary fiber and protein,and the textural property of composite gel were investigated in present study.The aim of this study was to expound the mechanism of myofibrillar protein gel influenced by modified sugarcane dietary fiber(SDF),so as to provide a theoretical basis for the application of sugarcane dietary fiber as fat replacement in low-fat sausage.【Method】The present study modified the physicochemical properties of sugarcane dietary fiber by hydrogen peroxide treatment.The myofibrillar protein with various concentrations and particle sizes of sugarcane dietary fiber were set as the model system.The treatment without SDF was the control;the treatment with 1%,2%and 3%50-mesh SDF addition respectively named T150,T250 and T350;the treatment with 1%,2%and 3%100-mesh SDF addition respectively named T100,T200 and T300.The dynamic rheological properties were analyzed by the rheometer;the true fracture stress and strain of composite gels were analyzed by the textural instrument;the spatial distribution of sugarcane dietary fiber in the MP gels were observed by the paraffin section,the microstructure and corresponding image analysis of myofibrillar protein gel networks were analyzed by the SEM and the image analysis software.【Result】With the increase of concentrations and particle sizes of sugarcane dietary fiber,the centrifugal loss of composite gel significantly reduced,while the storage module(G’)significantly increased.The result showed that the SDF addition significantly increased the fracture stress,while the SDF addition significantly reduced the fracture strain.Paraffin section showed that the sugarcane dietary fiber did not directly interact with protein.The dietary fiber just simply trapped in the protein networks and formed numerous various shapes and volumes cavities.The SEM showed that the myofibrillar protein networks under the control were filled with the connected moisture channels,and the existing of the moisture channel seriously hindered the interaction of the hydrophobic groupings,leading to the loose networks.The dietary fiber addition reduced the cross-linked moisture channels,and promoted the formation of compact and well-aggregated MP gel networks.The image analysis results showed that the treatment T350 had the highest fractal dimension value of 1.8670 and the lowest lacunary value of 0.19.【Conclusion】The composite gel was comprise of the frame structure formed by the heat-induced gel protein networks and the filled structure formed by the SDF as the filling phase and protein matrix as the continuous phase.The physicochemical properties of SDF proved that the water holding capability was correlated with the particle size.Hence,the treatment with 3%50-mesh sugarcane dietary fiber could promote the aggregation of myofibrillar protein through moisture stability,and had the highest stress.But the 50-mesh SDF was inelastic structure and formed various shapes and volumes cavities in gel networks,which significantly reduced the strain of composite gel.In conclusion,the 100-mesh SDF(smaller particle size)as fat replacement could significantly increase the stress of composite gel,and ultimately maintain the elasticity of the composite gel.