Whole-jabuticaba kombucha: a kinetic profile of acidity, anthocyanins, and antioxidant capacity

The growing interest in functional fermented beverages has driven research into alternative substrates for kombucha production, particularly Brazilian native fruits that remain technologically underexplored. Jabuticaba (Plinia cauliflora) stands out for its high concentration of anthocyanins and phenolic compounds, particularly in the peel, making it an attractive substrate for beverages with antioxidant potential. However, few studies have monitored the behavior of these compounds throughout fermentation when the whole fruit is incorporated into the process.

Given this gap, the present study monitored the physicochemical changes, bioactive compounds (anthocyanins and total phenolics), and antioxidant capacity (DPPH, ABTS, and FRAP) of a kombucha produced with whole jabuticaba fruit over 96 h of fermentation.

The starter tea was prepared with 5% (w/v) sucrose and 0.5% freeze-dried and ground whole jabuticaba fruit in 1 L of potable water. The mixture was boiled for 10 min, cooled to 30 °C, and inoculated with 20% (v/v) previously fermented liquid. Incubation was carried out at 30 °C for 96 h, with triplicate sampling at five time points (starter tea, 24, 48, 72, and 96 h). pH, total soluble solids (°Brix), volatile acidity (mEq/L), total phenolic content (Folin–Ciocalteu method), monomeric anthocyanin content (pH differential method), and antioxidant capacity (DPPH, ABTS, and FRAP) were determined. Data were subjected to one-way ANOVA followed by Tukey’s test (p < 0.05).

A significant reduction was observed in pH (3.60 to 2.74) and total soluble solids (7.40 to 6.60 °Brix), accompanied by a marked increase in volatile acidity (4.18 to 130.37 mEq/L). Total phenolic content fluctuated between 31.4 and 34.3 mg GAE/100 mL, with no linear trend. Anthocyanin content increased from 32.1 mg/L at the initial time point to values ranging from 35.6 to 37.1 mg/L at intermediate fermentation times. DPPH inhibition increased significantly (83.0% to 86.7%), as did FRAP values (1,600 to 6,706 µM TE/L), whereas ABTS values did not differ significantly among fermentation times.

The physicochemical behavior observed was typical of kombucha fermentation, reflecting sucrose hydrolysis and organic acid production by the SCOBY. The final volatile acidity approached the upper limit established by Brazilian legislation, indicating the need for fermentation-time control at larger production scales. The increase in anthocyanin content and antioxidant capacity (DPPH and FRAP) suggests greater release and/or biotransformation of these compounds, whereas the divergent response observed in the ABTS assay reinforces that different antioxidant assays capture distinct mechanisms.

Kombucha fermentation with whole jabuticaba fruit was shown to be viable, resulting in a beverage with physicochemical parameters compatible with Brazilian legislation, together with increased bioactive compound content and antioxidant capacity.

"This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001."