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
(C
CPC) 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 C
CPC. On the basis of the changed C
CPC, 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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