镁离子对绿茶纳米聚集体稳定性的影响及作用机制OA

This study aimed to elucidate the mechanisms by which Mg2+affects the stability of nano-aggregates in green tea infusions and the formation of tea cream.Dynamic light scattering(DLS),laser Doppler velocimetry(LDV)and transmission electron microscopy(TEM)were used to analyze the effect of Mg2+on the colloidal chemical properties and morphological characteristics of the nano-aggregates.The nano-aggregates were separated by ultrafiltration with different pore sizes,and the retention rates of major chemical components were determined by high performance liquid chromatography(HPLC)and ultraviolet-visible(UV-Vis)spectroscopy.Furthermore,a simple simulation system for green tea nano-aggregates was constructed using bovine serum albumin(BSA)and four catechin monomers.Fluorescence spectroscopy and circular dichroism(CD)spectroscopy were adopted to investigate the effect of Mg2+on the secondary structure of BSA and its interaction with catechins.Our results demonstrated that Mg2+neutralized the negative surface charges of nano-aggregates,reducing their electrostatic stability(indicated by a 78%decrease in the absolute zeta potential value).This promoted the further aggregation of tea polyphenols(particularly gallated catechins),caffeine,proteins,and soluble carbohydrates,leading to a near-doubling of the diameter of nano-aggregates and a decrease in their dispersibility.In the simulation system,Mg2+exerted a temperature-dependent dual effect on BSA-gallated catechin interactions.At 298 K,Mg2+induced a slight unfolding of BSA structure,creating a conformation that facilitated catechin binding.Conversely,at 310 K,Mg2+enhanced the structural rigidity of BSA,thereby hindering its interaction with gallated catechins.This study systematically analyzed the effect of Mg2+on the stability of green tea nano-aggregates from the perspectives of chemical composition,colloidal chemical properties,and catechin-protein interactions,providing theoretical support and a scientific basis for the prevention of tea cream in tea beverages.