Cross-flow microfiltration of traditional kombucha beverage using ceramic tubular membrane

The traditional kombucha beverage is produced through the metabolic activity of the microorganisms present in the kombucha culture on sweetened black tea at room temperature. The aim of this study was to investigate the influence of crossflow microfiltration on the quality of the produced beverage. The produced beverage was microfiltered to assess the effect of cross-flow microfiltration on its quality. The quality characteristics examined included pH, total acidity, total soluble solids, turbidity, organic acids, in vitro antioxidant potential, and vitamin C as an antioxidant compound. The operational parameters of the process were transmembrane pressure (0.2, 0.6, and 1 bar) and feed flow rate (30, 90, and 150 Lh^{-1} ). The maximum permeate flux was achieved at the highest feed flow rates and transmembrane pressures. Microfiltration maintained (pH, total acidity, total soluble solids, lactic, formic, and oxalic acid), improved (turbidity and acetic acid), but also declined (malonic acid, vitamin C, and antioxidant potential), the quality of the traditional beverage. After the microfiltration, turbidity was reduced by 7-9 times, and the content of acetic acid amounted to around 1.20 g/L. The lowering of acetic acid content indicated the inhibition of acid buildup. Values of the coefficient of retention for all of the examined quality parameters, except turbidity, suggested that the overall influence of microfiltration was moderate.