导　　师： 于淑娟

学科专业： 082202

授予学位： 硕士

作　　者： ;

机构地区： 华南理工大学

摘　　要： 本论文以乳清分离蛋白（WPI）和葡聚糖为主要原料，使用干热法制备WPI-糖接枝产物，对接枝物的理化性质、结构特征和功能特性进行了系统的研究，以期为蛋白质与多糖的接枝反应在食品工业中应用提供理论指导。 A294、褐变、游离氨基含量变化、SDS-PAGE图谱证实乳清分离蛋白与葡聚糖在干热处理条件下确实发生了以美拉德反应为机理的接枝反应；随着葡聚糖糖链的增加，其接入到蛋白质肽链的难度增加。由氨基酸分析可知，相对于原蛋白而言，接枝产物中赖氨酸和精氨酸的含量明显减少。接枝产物在405nm处的最大荧光强度均有显著提高，符合Maillard产物具有的荧光特征。外源荧光光谱、表面疏水性指数、溶解性指数的测定结果表明，以共价键形式接入的葡聚糖对乳清分离蛋白的疏水基团有一定的屏蔽作用，其表面疏水性明显降低。圆二色谱分析表明，接枝产物的α-螺旋和β-转角含量减少，β-折叠和无规则卷曲含量增加。扫描电子显微镜（SEM）研究发现，WPI分子的表面结构与其接枝物的明显不同，接枝物中并未出现典型的球状结构，而是以混乱的片状结构形式出现。 葡聚糖的共价接入，能够显著提高WPI的乳化性能和乳液的冻融稳定性，且电荷不是决定接枝产物乳液体系稳定性的主要因素。经接枝反应后，乳清分离蛋白的热变性温度有所提高；由于大分子糖链的接入，导致蛋白质分子在溶液中的空间位阻增大，能够有效抑制WPI的热聚集行为。接枝产物G150在热凝胶过程中的弹性模量G'和粘性模量G''曲线发生明显变化，这说明葡聚糖的引入改变了乳清分离蛋白的热凝胶机制。 乳清分离蛋白-葡聚糖接枝产物本身具有一定的抗氧化性，使用其作为壁材来制备微胶囊化鱼油产品，在获得良好微胶囊化效率和产率的同时，能够明显提高产品的抗氧化效果。 Whey protein isolate /(WPI/) and dextran were used to prepare WPI-dextran conjugate bythe dry-heating treatment in our present research. The physicochemical characteristics,conformation and functional properties of the conjugates were systematically investigated inorder to provide the theoretical knowledge, which could supply the guidance for theapplication of protein-polysaccharides grafted reaction in the food industry. Significant changes in A294, browning intensity, free amino groups content andSDS-PAGE profile showed that whey protein isolate-dextran conjugate was successfullyformed using dry-heating treatment via Maillard reaction. When the length of sugar chain wasincreased, the graft reaction was relatively difficult. Compared to the native WPI, the contentof lysine and arginine in the conjugate was decreased and the maximal fluorescence intensityat405nm was obviously increased, which was in accordance with the typical characteristic ofthe Maillard-type products. The measurement results of fluorescence, surface hydrophobicityindex and solubility index showed that the hydrophobicity of WPI could be suppressed due tothe covalent attachment of high molecular weight dextan chain. Far-UV CD spectra showedthat the α-helix and β-turns were decreased while β-sheet and random coil were increasedafter the WPI-dextran mixture was treated by the dry-heating. Moreover, it was observed bySEM that the surface structure of the conjugate WPI was different with the native WPI, whichwas that the typical globular structures was dispersed and the disordered sheet structureappeared. The emulsifying properties and the freeze–thaw stability of oil-in-water emulsionsstabilized by WPI were significantly enhanced by the covalent attachment of dextran; thecharge is not the main factor which determine the stability of the emulsion system after theξ-potential analysis. The thermal denaturation temperature of WPI was enhanced in somedegree by the glycosylation; the steric hindrance effect induced by the high molecular weightdextan chain could suppress the heat-induced aggregation among the neighbouring proteins inaqueous solution. During the gelation process, the modulus curve of G' and G'' in theWPI-dextran conjugate /(G150/) was significantly modified, which showed that the mechanismof gelation in WPI was intrinsically altered by the covalent attachment of dextran. The results showed that the WPI-dextran conjugate own strong DPPH radical scavenging ability, indicating that the antioxidant capacity of MRPs was increased. The conjugates wereused as wall material to encapsulate the fish oil and the data show that the core materialscould be well encapsulated with a high productive and efficiency. Meanwhile, the oxidativestability of the microcapsules products was highly enhanced.

关 键 词： 乳清分离蛋白 葡聚糖 美拉德反应

分 类 号： [TS201.2]

领　　域： [轻工技术与工程] [轻工技术与工程]