ISO/TS 5617:2025
(Main)Tea — Classification by chemical composition
Tea — Classification by chemical composition
This document specifies a method to classify six tea types (black tea, green tea, white tea, oolong (blue) tea, dark tea and yellow tea) based on statistical analysis of chemical compositions. The key X1 to X6 determinants (total catechins, caffeine, theanine, epigallocatechin gallate (EGCG)/total catechins, theanine × theanine, theanine × caffeine) for tea chemical classification were extracted from these critical compositions by statistical methods, from a large-scale chemical analysis of samples of six tea types, which can be used as principal components to classify the particular tea by Fisher’s step-by-step discrimination formulae.[6][7] This document is applicable to the classification of both primary and refined teas, and is particularly suitable for teas produced in China. It does not apply to reprocessed teas.
Thé — Classification par composition chimique
General Information
Standards Content (Sample)
Technical
Specification
ISO/TS 5617
First edition
Tea — Classification by chemical
2025-09
composition
Thé — Classification par composition chimique
Reference number
ISO/TS 5617:2025(en)
© ISO 2025
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ii
ISO/TS 5617:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principal components statistical and principle of Fisher’s discrimination method . 2
5 Reagents . 3
6 Apparatus . 3
7 Sampling . 3
8 Preparation of testing samples . 3
9 Quantification of the characteristic compositions in the unknown-type tea . 3
9.1 Determination of dry matter content . .3
9.2 Determination of catechins and caffeine content .4
9.3 Determination of theanine content .4
10 Step-by-step discrimination using Fisher’s discrimination method. 4
10.1 General .4
10.2 Establishing discrimination formulae .4
10.2.1 Principal components analysis .4
10.2.2 Establishing the discrimination formulae .4
10.2.3 Validating the discrimination formulae .4
10.3 Identifying unknown tea types .5
10.3.1 General discrimination steps .5
10.3.2 First step: Discrimination of high aeration or piling fermentation teas (black
tea, dark tea) from none or lower aeration teas (white tea, oolong tea, green tea,
yellow tea) .5
10.3.3 Second step: Discrimination of black tea from dark tea .6
10.3.4 Third step: Discrimination of white tea from oolong tea, green tea and yellow tea .6
10.3.5 Fourth step: Discrimination of oolong tea from green tea and yellow tea .6
10.3.6 Fifth step: Discrimination of green tea from yellow tea .6
10.3.7 Sixth step: Discrimination of black tea from white tea .7
11 Simplifying the discrimination process using designed software (optional) . 7
12 Re-discriminating a disputed tea type . 7
Annex A (informative) Sources, quantities and content of characteristic chemical compositions
of the six tea types . 8
Annex B (informative) Tea classification .11
Bibliography . 14
iii
ISO/TS 5617:2025(en)
Foreword
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of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
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This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 8, Tea.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv
ISO/TS 5617:2025(en)
Introduction
Tea is a popular and healthy beverage, derived from the processed young shoots of the tea plant Camellia
sinensis. Generally, tea can be classified into two categories: basic teas and reprocessed teas. According to
ISO 20715, the basic teas in the tea market are classified into six tea types, based on their characteristic
manufacturing techniques and oxidation degree in processing: black tea, green tea, white tea, oolong tea,
dark tea and yellow tea. Beside the basic teas, there are many reprocessed teas such as flavoured tea,
teabags, decaffeinated tea and flavoured tea with other food ingredients, which all belong to the derivatives
of basic teas. The most commonly teas found in the market are black tea, green tea, oolong tea and white tea.
Recently, the market for dark tea and yellow tea has been rapidly growing.
To date, most of the knowledge surrounding tea classification has been based on the processing method and
the aeration/oxidation (also called “fermentation”) extent of tea polyphenols, especially catechins in fresh
tea leaves after being plucked. The characteristic processing techniques of different teas are as follows:
— aeration/oxidation/fermentation (black tea);
— enzyme inactivation/fixation (green tea);
— long-time withering (white tea);
— tumbling by shaking and bruising (oolong tea);
— piling fermentation (dark tea);
— yellowing (yellow tea).
In ISO 3720:2011 for black tea, the minimum of total polyphenols content is a mass fraction of 9,0 %, while in
ISO 11287:2011 for green tea and ISO 20716:2022 for oolong tea, the minimum of total polyphenols content
is a mass fraction of 11 % and 10,0 %, respectively. Moreover, in ISO 11287:2011, the total catechins and the
ratio of total catechins to total polyphenols are required to be a mass fraction of 7 % and 0,5 %, respectively,
and in ISO 20716:2022, they are required to be a mass fraction of 3,0 % and 0,3 %, respectively. Apart from
total polyphenols and total catechins, the distinct processing of the six tea types greatly affects the dynamic
changes of the abundant chemical compositions such as phenolic acids, caffeine, free amino acids, theanine
and flavonoids in different aeration/oxidation degrees. This provides a feasible approach to discriminate
the different tea types by analysing their contents based on the existing International Standards for tea (see
ISO 14502-2:2005 and ISO 19563:2017). The method by chemical analysis provides an auxiliary approach to
classify the basic tea types of a particular test sample by the processing methods and a traditional sensory
evaluation by professional tea panels.
This document classifies the basic tea types based on statistical analysis of chemical compositions. Due to the
complexity and intended scope of this document, this edition limits the classification to primarily Chinese
teas. The collected database is not yet sufficient to ensure general validity for teas of all types and origins
worldwide. Among other things, teas from different growing regions in individual countries, as well as the
influence of seasonality, have not yet been adequately considered. Samples that take these parameters into
account were not provided in sufficient quantities or were not available. The accuracy of the discrimination
method for tea-type classification was 85 % in this document, with the intention that it should be at least
90 % or even at least 95 % in the next revision of this document.
v
Technical Specification ISO/TS 5617:2025(en)
Tea — Classification by chemical composition
1 Scope
This document specifies a method to classify six tea types (black tea, green tea, white tea, oolong (blue) tea,
dark tea and yellow tea) based on statistical analysis of chemical compositions. The key X to X determinants
1 6
(total catechins, caffeine, theanine, epigallocatechin gallate (EGCG)/total catechins, theanine × theanine,
theanine × caffeine) for tea chemical classification were extracted from these critical compositions by
statistical methods, from a large-scale chemical analysis of samples of six tea types, which can be used as
[6][7]
principal components to classify the particular tea by Fisher’s step-by-step discrimination formulae.
This document is applicable to the classification of both primary and refined teas, and is particularly suitable
for teas produced in China. It does not apply to reprocessed teas.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendmen
...
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