Determination of Organic Acids in Kombucha Using a High-Pressure Ion Chromatography System

Importance of the Topic

Kombucha is a fermented tea-based beverage valued for its health-promoting organic acids, which influence both functional properties and sensory attributes. Reliable quantification of these acids is essential for consistent quality control, safety assurance, and flavor optimization in commercial products.

Objectives and Study Overview

This study aimed to develop a robust high-pressure ion chromatography (HPIC) method with suppressed conductivity detection to accurately profile key organic acids in kombucha. It covers method optimization using an on-line KOH gradient, analytical validation, and application to multiple commercial samples.

Methodology

• Sample preparation: centrifugation at 6500–7500 g, 0.2 µm filtration, followed by 1:20 dilution in deionized water
• Eluent generation: on-line KOH gradient from 1 to 60 mM with up to 15 % methanol modifier to enhance separation
• Chromatographic conditions: Dionex IonPac AG11-HC guard (2×50 mm) and AS11-HC analytical (2×250 mm) columns, 45 °C, 0.45 mL/min flow, 2.5 µL injection
• Detection: Dionex AERS 500 anion suppressor operated in external water mode with suppressed conductivity readout

Instrumentation

• Dionex ICS-5000+ HPIC system comprising pump, eluent generator, and detector modules
• AS-AP autosampler equipped with a 250 µL sample syringe
• EGC 500 KOH eluent generator cartridge, CR-ATC 500 continuously regenerated trap column, and AERS 500 suppressor
• Chromeleon 7.2 chromatography data system software

Main Results and Discussion

The optimized method resolved twenty inorganic and organic anions and quantified eight major organic acids—acetic, gluconic, lactic, pyruvic, succinic, malic, oxalic, and citric—in three kombucha brands. Glucuronic acid was not detected. Calibration curves exhibited coefficients of determination ≥ 0.9996, with limits of detection between 0.006 and 0.057 mg/L and limits of quantitation from 0.02 to 0.19 mg/L. Precision tests yielded retention time RSDs below 0.1 % and peak area RSDs under 7 %. Recovery experiments for acetate, succinate, and citrate ranged from 81 % to 115 %, confirming method accuracy. Variations in acid profiles among samples reflected differences in fermentation processes.

Benefits and Practical Applications

• High sensitivity and resolution for complex beverage matrices
• Minimal interference from sugars and phenolic compounds
• Streamlined solvent management via on-line eluent generation
• Simplified sample preparation without derivatization steps
• Suitable for routine QA/QC in kombucha and related products

Future Trends and Potential Uses

• Coupling HPIC with mass spectrometry for enhanced compound identification
• Development of eco-friendly solvents and novel ion-exchange phases
• Increased automation and on-line sample processing for higher throughput
• Extension of the approach to other fermented foods and beverages

Conclusion

The presented HPIC method using the Dionex IonPac AS11-HC-4 µm column and ICS-5000+ system delivers a precise, accurate, and sensitive platform for organic acid analysis in kombucha, supporting quality control and research in functional beverage development.

References

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4. Thermo Fisher Scientific. Product Manual for Eluent Generator Cartridges, P/N 065018. Sunnyvale, CA, 2012.
5. Thermo Fisher Scientific. Product Manual for Continuously Regenerated Trap Columns (CR-TC), Doc. No 031910. Sunnyvale, CA, 2010.
6. Thermo Fisher Scientific. Product Manual for Dionex ERS 500 Suppressor, Doc No 031956. Sunnyvale, CA, 2013.