Effects of Extraction Method on the Physicochemical Profiles and Colloidal Properties of Green Tea Cream
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Abstract:
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.
