BACKGROUND: Removing excessive naturally occurring fluoride from tea and/or infusions is difficult because the process has low efficiency and causes secondary pollution. In this study, a novel electrodialysis (ED) technology was developed. We examined the effect of crucial parameters (electrolyte concentration, operation voltage, ED duration, and initial concentration of the tea infusion) on the defluoridation performance by using a highly efficient ion exchange membrane with five?compartment cells.

RESULTS: The most effective ED system results were obtained at an electrolyte concentration of 10 g•kg^-1 and operation voltage of 20 V. Moreover, the fluoride removal capacity (10.70%–66.93%) was highly dependent on the ED duration (1–15 min) and initial concentration of the tea infusion (0.5 g•kg^–110 g•kg^–1). The longer the ED duration and lower the initial concentration, the higher was the defluoridation performance. During ED, limited loss of the main inclusions (total polyphenols, catechins, caffeine, and selected ions) was observed. Furthermore, the D201 anion resin-filled ED stack (0.5 g – 5 g) and improvement of concentrate compartment electrolyte (>5 times of dilute compartment electrolyte) in the ED system enhanced the defluoridation rate significantly.

CONCLUSION: ED is a potentially effective method that can be used for defluoridation in the deep-processing of tea products.

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*Original abstract online at https://onlinelibrary.wiley.com/doi/abs/10.1002/jsfa.10011