Effects of Tea-Polysaccharide Conjugates and Metal Ions on Precipitate Formation by Epigallocatechin Gallate and Caffeine, the Key Components of Green Tea Infusion.
The mechanism of tea-infusion precipitation is not clear. Epigallocatechin gallate (EGCG) and caffeine (CAF) are the core components of green tea infusion precipitate. The critical precipitation concentration ( CCPC) of EGCG-CAF mixed aqueous solutions was assayed through a turbidity assay performed at 25 °C and verified by a differential-scanning calorimeter (DSC) for reliability. Different concentrations of the green tea polysaccharide conjugate fraction (gTPC-D), with a molecular weight of 2.32 × 105 Da, and of metal ions (K+, Mg2+, Ca2+, and Al3+) were respectively introduced into the mixed solution to study their effects on CCPC. On the basis of the changed CCPC, the clarification-precipitation phase diagrams of the mixed aqueous solutions were constructed. By calculating the integral area of the clarification phase, it was determined that the four metal ions and gTPC-D could accelerate precipitate formation with a dose-response relationship; among the metal ions, the effect of Al3+ is the strongest, followed by that of Ca2+.
['Chen|Xiaoqiang|X|http://orcid.org/0000-0002-3379-9870', 'Du|Yu|Y|', 'Wu|Long|L|', 'Xie|Jianchun|J|http://orcid.org/0000-0002-7403-9288', 'Chen|Xueling|X|', 'Hu|Binbin|B|', 'Wu|Zhengqi|Z|', 'Yao|Qifeng|Q|', 'Li|Qian|Q|']
D002110:Caffeine D002392:Catechin D011232:Chemical Precipitation D007477:Ions D008670:Metals D011134:Polysaccharides D013662:Tea
tea-polysaccharide conjugates metal ions precipitation caffeine green tea infusion epigallocatechin gallate (EGCG)