Retention of Original Flavor Characteristics in Defluorinated Instant Qingzhuan Brick Tea Prepared Using Membrane Separation Technology

Brick tea is a type of post-fermented food that involves microorganisms. Long-term consumption of brick tea exposes consumers to high fluoride levels, which can adversely affect their health. This study explored the feasibility of selective defluorination of Qingzhuan brick tea through membrane separation technology, and pilot production was conducted to produce defluorinated instant brick tea. The concentration of tea polyphenols increased by more than 10 times after nanofiltration, demonstrating the high selectivity of nanofiltration membranes toward fluoride. Defluorination trends were studied at different initial material concentrations (0.5–4%) and operating pressures (0.1–0.5 MPa) under cyclic defluorination. Defluorinated instant brick tea products were also industrially prepared using 300- (DF-300) and 1000-Da (DF-1000) membranes, followed by vacuum freeze-drying. The DF-1000 and DF-300 products exhibited a defluorination rate of 51.46% and 67.96%, respectively. The products have excellent characteristics in terms of color, aroma, and flavor quality, as well as solubility. Gas chromatography–mass spectrometry indicated that the volatile components in the defluorinated instant brick tea were slightly different from those in the original tea, but the key aroma and flavor characteristics of the defluorinated brick tea remained unchanged. Membrane separation provides technical support for the large-scale production of low-fluoride post-fermented tea.