茶多酚对大米淀粉糊化特性影响的机制研究

Tea polyphenols (TPLs) was found to significantly change the characteristics of starch and was attempted to become a new method to regulate starch characteristics with safety, high efficiency, or health care function. However, the mechanisms of the effects of TPLs on the characteristics of starch are unclear. Therefore, main compounds of TPLs and rice starch were studied as research objects in this project. The effects of different concentrations of these main components on the gelatinization characteristics (including viscosity, rheological, and thermal characteristics) of rice starch were systematically studied to reveal the regularity of the influence and determine effective components of TPLs. Then, the corresponding relations between properties of effective components of TPLs and the influences on gelatinization characteristics of rice starch were studied and established. In addition, the intermolecular interactions of TPLs effective components-starch-water in the gelatinization system were discussed. Based on these researches, the mechanism of the effects of TPLs on the gelatinization characteristics of rice starch was clarified. This mechanism could lay the foundation to effectively control the gelatinization characteristics of starch. Moreover, these studies were attempted to rich the interaction mechanisms of exogenous micromolecules and starch macromoleculars, and provide theory bases for the reasonable and scientific application of TPLs on starchy food processing.

茶多酚能显著影响淀粉特性，有望成为调控淀粉特性的安全、高效或及保健功能于一体的新型物质，但其对淀粉特性影响的机制尚不清楚。因此，本项目以茶多酚中主要组分和大米淀粉为研究对象，系统研究这些主要组分在不同浓度下对淀粉糊化特性（包括粘度、流变和热特性）影响，揭示影响的规律性，明确具有影响作用的茶多酚有效组分；建立茶多酚有效组分性质与能影响淀粉糊化特性的关系；探讨糊化体系中茶多酚有效组分-淀粉-水分三者分子间相互作用。研究将阐明茶多酚对大米淀粉糊化特性影响的机制，为日后利用茶多酚调控淀粉糊化特性提供理论依据。此外，该研究还可以丰富外源小分子与淀粉大分子相互作用机理，有利于茶多酚在淀粉类食品加工中合理、科学地应用。

由于对茶多酚保健功能的推崇，添加茶多酚的淀粉类米面制品早已上市销售。而茶多酚能够显著影响淀粉特性，但对其机制研究并不透彻。因此，本项目以茶多酚中三种主要儿茶素化合物和大米淀粉为研究对象，系统研究茶多酚中主要组分对大米淀粉粘度、热特性、流变和质构特性的影响，揭示其影响规律性，明确具有影响作用的茶多酚有效组分。通过本项目的研究为茶多酚及其儿茶素化合物在淀粉类食品加工中合理、科学应用奠定扎实的理论基础，也为解决提高淀粉类制品品质和延长货架期等技术难题开辟新的解决途径。.本项目研究发现，三种儿茶素化合物表儿茶素（EC）、表没食子儿茶素（EGC）和表没食子儿茶素没食子酸酯（EGCG）对大米淀粉糊化特性具有显著影响。首先，通过RVA研究发现，三种儿茶素化合物均能显著提高大米淀粉的崩解值，降低大米淀粉的回生值。说明儿茶素能降低大米淀粉的热糊稳定性和抑制淀粉回生。其次，DSC分析发现，三种儿茶素化合物能显著降低大米淀粉糊化温度，但对大米淀粉糊化焓值没有显著影响，这与之前的茶多酚提取物能显著降低大米淀粉糊化焓值的研究结果不一致。在4℃下贮藏10d后，三种儿茶素对大米淀粉回生焓值无显著影响；但贮藏20d后，与空白相比（∆Hr为5.25±0.15J/g），三种儿茶素能明显降低大米淀粉的回生焓值，及降低相应的回生率。贮藏30d后，添加三种儿茶素的样品与空白样品的回生焓值并无显著差异。以上结果说明，三种儿茶素化合物对大米回生初期没有抑制作用，随着时间的延长能够抑制其回生，但是随着回生的进行，对其回生的抑制作用逐渐减弱。再者，动态升温流变分析发现，所有样品在整个加热阶段，贮能模量G'始终大于粘性模量G"，表明大米淀粉即使在儿茶素存在下其凝胶弹性也是大于粘性的，即大米淀粉糊倾向于类似固体的凝胶。同时，在不同加热速率下，儿茶素均降低大米淀粉的G'和G"，说明在儿茶素存在情况下大米淀粉越容易受外界作用力影响发生变形、流动，这与儿茶素能降低大米淀粉崩解值结果相一致。最后，三种儿茶素均能降低大米淀粉凝胶在贮藏过程中的硬度，再次证明了儿茶素可以抑制大米淀粉回生。.在三种儿茶素中，EGCG对大米淀粉的糊化特性影响最为显著，推测可能与其羟基反应活性最强有关。