Overview
ISO/TS 5617:2025 - Tea: Classification by chemical composition specifies a laboratory and statistical method to classify six basic tea types (black, green, white, oolong, dark and yellow) using chemical composition data. The Technical Specification extracts six principal discriminant factors (X1–X6) - total catechins, caffeine, theanine, EGCG/total catechins, theanine × theanine, and theanine × caffeine - from large-scale analyses and applies principal components analysis and Fisher’s step‑by‑step discrimination formulae to identify tea type. The method is applicable to primary and refined teas (not reprocessed teas) and is currently particularly suitable for teas produced in China. Reported classification accuracy for this edition is about 85%, with targets for improvement in future revisions.
Key topics and requirements
- Scope and applicability: Classification of six basic tea types by chemical profiles; excludes reprocessed teas.
- Sampling and sample preparation: Follows ISO sampling and sample-prep principles (e.g., ISO 1839, ISO 1572).
- Quantification of markers: Determination of dry matter, catechins, caffeine and theanine using established ISO analytical methods (see ISO 14502‑2 and ISO 19563 - HPLC‑based methods are referenced).
- Statistical methods: Use of principal components analysis (PCA) to extract discriminant factors and Fisher’s step‑by‑step discrimination to establish and validate classification formulae.
- Stepwise discrimination process: A multi-step decision sequence (e.g., separating high‑fermentation from low‑fermentation teas, then finer distinctions) with optional supporting software and procedures for re‑discrimination of disputed samples.
- Validation and limits: Document describes validation procedures and notes current geographic/sample limitations; accuracy and database coverage expected to be expanded over future revisions.
Applications and users
Practical uses include:
- Quality control and tea authentication in analytical laboratories.
- Regulatory and customs testing where objective chemical classification complements sensory and processing-based standards.
- R&D and provenance studies for tea manufacturers, packers and research institutes.
- Support for standards bodies and certification schemes seeking reproducible, chemistry‑based tea classification.
Typical users:
- Accredited testing laboratories, tea processors and exporters, regulatory agencies, tea research centers, and standardization committees.
Related standards
ISO/TS 5617:2025 provides an objective, chemistry‑driven complement to processing‑ and sensory‑based tea classification methods, enabling more reproducible identification and supporting traceability, quality assurance and research in the tea sector.