绿茶提取液沉淀形成机理的研究

The Mechanism of Sediment Formation in Green Tea Beverage

以绿茶为试验材料,从茶汤体系的物化性质和化学成分两方面探讨了茶汤沉淀形成的机理。通过对沉淀形成过程中沉淀颗粒形态变化、电解质和氢键裂解剂的作用、红外光谱变化等内容的研究,来判断茶汤形成沉淀前后的性质改变,初步判定经低温贮存后的茶汤体系介于胶体分散系和粗分散系;茶汤颗粒间的氢键、静电作用是影响茶汤沉淀形成的因素,共价键不是沉淀形成的主要因素。通过计算茶汤中各主要成分进入上清相和沉淀相的分配系数,来判断该成分进入上清相和沉淀相的趋势,结果表明:茶多酚是构成茶汤沉淀物的主体物质,其次是果胶、咖啡碱,而在沉淀相中分配系数较大的成分依次是叶绿素、没食子酸、果胶、蛋白质、花青素、咖啡碱、可可碱。

The mechanism of sediment formation in green tea beverage were studied based on the chemical elements and infusion system in green tea extraction. The viscosity character, micrograph of tea cream particles and IR spectrum of tea infusion were compared between original tea infusion and stored tea infusion. Effects of NaCl on turbid of tea infusion and guanidine hydroehloride on the viseosity of tea infusion were also investigated. The results showed that the hydrogen bond and ion bond in tea infusion system caused sediment formation, while covalent bond was not a major factor. The phase of green tea infusion stored at low temper- ature was between the colloid and dispersed phase, which was confirmed according to the shape of tea cream particles. An effective distribution coefficient KA was introduced in this study to estimate the diffusing tend- ency of components in tea infusion to supernatant or sediment part. The results showed that polyphenol was the main component contributed to the sediment formation, and then the protein and caffeine. However, KA of main components in green tea infusion showed that the primary components affected the sediment formation from strongest to weakest was chlorophy, gallic acid, pectin, protein, anthocyanin anthocyanin and caffeine. Key words green tea extract,sediment formation, mechanism, distribution coefficient, interaction