为探究浸提方式对绿茶沉淀形成的影响及其可能机制，本研究采用微波、超声波、水浴浸提云南大叶种绿茶，利用动态光散射等技术分析茶汤胶粒与沉淀颗粒的胶体特性，利用高效液相色谱等技术测定其理化组成，利用逐步回归法分析各组分沉淀浓度与茶汤浓度的线性相关性，发现：微波浸提茶汤胶粒数目仅约为沸水浴的57%，但其沉淀总量、总沉淀率均显著高于后者，微波浸提绿茶沉淀总量主要与茶汤酯型/非酯型儿茶素、酯型儿茶素/生物碱比例呈显著正相关（R2为0.972），而水浴浸提绿茶沉淀总量与茶汤生物碱浓度呈显著正相关（R2为0.969）；超声波浸提显著降低茶汤胶粒与沉淀颗粒直径，但其沉淀总量、总沉淀率均与水浴浸提相当，且沉淀总量仅与茶汤蛋白质、生物碱浓度呈较弱正相关（R2为0.632）。浸提方式不仅影响绿茶沉淀胶体特性与理化组成，并可能改变沉淀形成的量效机制。

To explore the effects of extraction method on the formation of green tea cream and the potential underlying mechanisms, Yunnan “large-leaf” green tea samples were extracted using a water bath, a microwave, and ultrasonography. The colloidal properties of the particles in original infusions and the green tea cream were analyzed using dynamic light scattering and other techniques, and corresponding physicochemical profiles were determined with high-performance liquid chromatography. The linearity between the cream concentration and infusion concentration in each fraction was analyzed by stepwise regression analysis. The results showed that the number of the infusion particles extracted by ultrasonography was only 53% that of the infusion particles extracted by the water bath. However, the ultrasound-assisted extraction gave higher total cream amount and total creaming rate compared with those by water bath extraction. The amount of total cream in green tea extracted with the microwave was linearly correlated with the ratios of gallated catechins to nongallated catechins and of gallated catechins to methylxanthine alkaloids in the original infusions (R2 = 0.972). In contrast, the amount of total cream in green tea extracted using the water bath was significantly correlated with the original concentration of methylxanthine alkaloids (R2 = 0.969) in infusions. Ultrasound-assisted extraction significantly reduced the diameters of colloidal particles in infusions and cream particles, but did not alter the total cream amounts or total creaming rates relative to those of water bath extraction. Additionally, the amount of total cream in the ultrasound-assisted extract exhibited a weak linear correlation (R2 = 0.632) with the concentrations of protein and methylxanthine alkaloids in the infusion. In conclusion, extraction methods can not only affect the colloidal properties and physicochemical profiles of green tea cream, but also alter the concentration-dependent mechanisms of cream formation.

农业部现代茶叶产业技术体系专项资金（CARS-23）；高等学校博士学科点专项科研基金联合资助项目（20124404110015）