Chen X, Du Y, Wu L, Xie J, Chen X, Hu B, Wu Z, Yao Q, Li Q. Effects of Tea-Polysaccharide Conjugates and Metal Ions on Precipitate Formation by Epigallocatechin Gallate and Caffeine, the Key Components of Green Tea Infusion.
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019;
67:3744-3751. [PMID:
30788964 DOI:
10.1021/acs.jafc.8b06681]
[Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
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+.
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