Effects of Interlayer Ion in Montmorillonite on Appearance of Decaffeinated Tea Beverage

Abstract

We examined changes in the appearance of green tea decaffeinated by montmorillonite (MMT) and the effects of interlayer ion in MMT on the appearance of decaffeinated green tea. After MMT treatment, turbidity was generated in decaffeinated green tea over time and was suggested to be due to precipitation of calcium oxalate generated by a reaction between Ca ion released from the interlayer of MMT and oxalate ion in green tea. Exchanging the interlayer ion in MMT with Na, K, Mg or NH₄ ion suppressed the precipitation of calcium oxalate in decaffeinated green tea, such that turbidity after decaffeination was not observed. The ion-exchanged MMTs (K, Mg or NH₄-MMT) had similar caffeine adsorption abilities on the decaffeination of green tea. Our findings suggest that ion-exchanged MMT can remove caffeine in green tea and maintain the appearance quality.