甘油三酯分子极性诱导猪肉蛋白质定向吸附特性转变机制研究

Reducing the animal fat content in emulsion-type meat products would decrease water-holding capacity and generate poor palatability, and how to improve product qualities and reduce the defects due to the decrease of animal fat content has been one of the research priorities of the current meat science. Summarizing the previous investigation, we found that occurring of different conformational changes of meat protein was induced by different types of fat. Based on this finding, we propose a hypothesis that the morphological changes of triglycerides could induce the adsorption transition of meat protein at the oil-water interface. This project protocols to select the meat batters as carrier, change the fatty acid composition and the esterification degree to get different morphological fats. With the help of high-performance liquid chromatography, mass spectrometry and Raman spectroscopy, effects of fatty acid composition, structure and crystal form on meat protein secondary structure, hydrophobic group and active sulfhydryl would be evaluated, then further to build relationships between triglycerides morphological changes and meat protein conformational transformation in the emulsification process. By the way of changing triglycerides structure to control the composition of fatty acid at the interface lipid phase, tracing the regularity of interfacial lipid fatty acid polarity induced the changes of protein membrane adsorption kinetics, interfacial expansion and stability, and then analyzing the adsorption transition mechanism of meat protein adsorption characteristics induced by triglycerides morphological changes, and ultimately clarify the reason for the changes of meat gel matrix, interfacial protein membrane and oil phase induced by the animal fat content reduction. The results would be useful to provide the theoretical foundation for the research and development of high-quality low-fat meat products.

降低乳化型肉制品中动物脂肪含量可降低制品的持水性和口感，如何改善由此而造成的产品质量缺陷是当前肉品科学研究领域的重点之一。我们的前期研究发现不同类型的脂肪会诱导肌肉蛋白发生不同的构象变化，据此我们提出“甘油三酯分子极性诱导肌肉蛋白质定向吸附特性转变”的假说。本项目拟以肉糜体系为载体，通过改变脂肪酸组成得到不同极性的脂肪，借助高效液相色谱、质谱、拉曼光谱等分析脂肪酸组成、结构及晶型对肌肉蛋白质二级结构、疏水基团、活性巯基的影响，建立乳化过程中甘油三酯分子极性与肌肉蛋白质构象变化之间的关系；利用甘油三酯分子极性的变化调控界面脂相，通过跟踪界面脂相脂肪酸特性诱导界面蛋白膜吸附动力学、界面扩张及稳定性发生改变的规律，解析甘油三酯分子极性诱导肌肉蛋白质发生吸附特性转变机制，并最终阐明因降低肉糜中动物脂肪含量诱导其凝胶基质、界面蛋白膜及脂相发生改变的原因。旨在为研究开发优质低脂肉制品提供理论依据。

本项目以不同组成甘油三酯的肉糜体系为研究对象，应用高效液相色谱、质谱、拉曼光谱、界面流变等技术，研究了脂肪酸极性、饱和程度、链的长短等对猪肉蛋白质乳化特性的影响。结果显示（1）随着脂肪酸饱和度的降低，乳液的乳化稳定性逐渐降低；而脂肪酸的组成、饱和程度和极性影响参与乳化的蛋白质构象变化，二硫键和疏水相互作用是蛋白质乳化过程中涉及的主要化学作用力；甘油三酯的分子构成及结构决定了脂肪与猪肉盐溶性蛋白质互作的方式，进而影响肉糜（乳浊液）的乳化凝胶特性，造成了肉糜质构及保油保水性出现差异。（2）脂肪酸的饱和程度影响界面蛋白膜的二级结构，不饱和脂肪酸含量越高，界面膜蛋白分子的表面疏水性和活性巯基含量越少，界面膜上蛋白质分子的α-螺旋含量也越少，β-折叠含量越多，因此界面蛋白膜的蛋白质分子展开程度越高；脂肪酸极性对蛋白质的乳化活性影响较大，但极性脂肪酸含量多，单位界面膜吸附的蛋白量少，界面蛋白膜上蛋白质分子的展开程度越大；甘油三酯分子中脂肪酸极性和链的长短对肌原纤维蛋白的乳化活性和乳化稳定性影响大于脂肪酸的饱和程度。此外，相变温度可为肉糜乳化凝胶的水分分布和迁移以及蛋白质的构象变化提供关键信息，而甘油三酯分子（或脂肪酸）的组成和结构直接影响乳化肉糜的相变温度。综上，甘油三酯分子极性、饱和程度、链的长短均可通过诱导界面蛋白分子的展开程度来调控界面蛋白膜的吸附特性，进而影响肉糜的质构和保油保水性。