Overview
ISO 18447:2021 - Tea - Determination of theaflavins in black tea - Method using high performance liquid chromatography defines a validated HPLC/UHPLC procedure for quantifying the four major theaflavins in tea. The standard applies to leaf and instant black and oolong teas (not validated for ready-to-drink/RTD beverages) and specifies extraction, chromatographic conditions, calibration approaches and reporting requirements for reproducible theaflavin analysis.
Keywords: ISO 18447:2021, theaflavins, black tea, HPLC, UHPLC, tea analysis, tea quality, chromatographic method
Key topics and technical requirements
- Analytes covered: the four major theaflavins - TF, TF‑3‑gallate, TF‑3′‑gallate and TF‑3,3′‑digallate.
- Method type: Reversed‑phase HPLC or UHPLC with isocratic elution and UV detection (primary wavelength 274 nm; 375 nm optional).
- Sample scope: Finely ground leaf tea and instant tea (leaf extraction and instant tea dissolution procedures described). Not validated for RTD beverages.
- Extraction and stabilization: Leaf extraction with 70% methanol at 70 °C; instant tea dissolved in hot water with acetonitrile stabilizer. Antioxidants/chelators (ascorbic acid, EDTA) used to stabilize extracts.
- Calibration: External theaflavin standards of known purity and moisture content are preferred. Alternatively, a caffeine external standard may be used together with consensus relative response factors (RRFs) established through ISO interlaboratory testing.
- Reagents and mobile phases: HPLC-grade methanol, acetonitrile, acetic acid, water (ISO 3696 grade) and stabilizer solutions specified. Mobile phases include acidified aqueous and acetonitrile phases (2% acetic acid).
- Quality and precision: The standard includes interlaboratory test results, repeatability and reproducibility guidance, and requirements for test reporting.
Practical applications
- Quality control and specification testing for black and oolong tea producers and packers.
- Product development and process optimization to monitor fermentation and oxidation (theaflavin formation).
- Research laboratories studying tea chemistry, health-related components or processing effects.
- Regulatory and certification bodies requiring traceable, standardized quantitation of theaflavins for labeling, trade or conformity assessment.
Who should use this standard
- Analytical laboratories performing tea composition testing
- Tea manufacturers and ingredient suppliers for QC and shelf‑life studies
- Food scientists and academic researchers focusing on polyphenol analyses
Related standards
- ISO 1572 - Preparation of ground sample of known dry matter content (tea)
- ISO 3696 - Water for analytical laboratory use - Specification and test methods
- ISO 7513 - Instant tea - Determination of moisture content
This ISO method provides a standardized, reproducible HPLC/UHPLC workflow for accurate theaflavin quantitation - a key metric in assessing black/oolong tea quality and processing outcomes.