ISO/TS 5617:2025

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
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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this may not represent the latest information, which may be obtained from the patent database available at
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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
complete listing of these bodies can be found at www.iso.org/members.html.

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 amendments) applies.
ISO 1572:1980, Tea — Preparation of ground sample of known dry matter content
ISO 1573:1980, Tea — Determination of loss in mass at 103 degrees C
ISO 1839:1980, Tea — Sampling
ISO 14502-2:2005, Determination of substances characteristic of green and black tea — Part 2: Content of
catechins in green tea — Method using high-performance liquid chromatography
ISO 19563:2017, Determination of theanine in tea and instant tea in solid form using high-performance liquid
chromatography
3  Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
discriminant factor
factor extracted by statistical method from the characteristic compositions which are the main compounds
in tea that significantly contribute to tea quality
3.2
step-by-step discrimination
chemical classification of teas that is based on large-scale data on the major characteristic components
determined in all six tea types by existing ISO methods on teas
Note 1 to entry: The formulae to identify the type of a particular tea are established step by step.

ISO/TS 5617:2025(en)
3.3
black tea
tea derived solely and exclusively, and produced by acceptable processes, notably withering, leaf maceration,
aeration and drying, from the tender shoots of varieties of the species Camellia sinensis (L.) O. Kuntze, known
to be suitable for making tea for consumption as a beverage
[SOURCE: ISO 3720:2011, 3.1]
3.4
green tea
tea derived solely and exclusively, and produced by acceptable processes, notably enzyme inactivation and
commonly rolling or comminution, followed by drying, from the tender leaves, buds, and shoots of varieties
of the species Camellia sinensis (L.) O. Kuntze, known to be suitable for making tea for consumption as a
beverage
[SOURCE: ISO 11287:2011, 3.1]
3.5
white tea
tea obtained solely and exclusively by acceptable processes of harvesting, withering and drying, made from
the buds, or the buds and tender leaves, or only the leaves of Camellia sinensis (L.) O. Kuntze varieties that are
suitable for the preparation of tea for consumption as a beverage
Note 1 to entry: White tea is made exclusively from buds for Baihao Yinzhen (formerly known as Silver Tip/Needle);
from buds and tender leaves for Bai Mudan (formerly known as White Peony); and from leaves for Shoumei.
Note 2 to entry: For processed white tea, cutting is allowed.
Note 3 to entry: Includes products from different geographic origins that follow this processing protocol.
1)
[SOURCE: ISO 20680:—, 3.1, modified — Note 2 to entry deleted and subsequent notes renumbered
accordingly.]
3.6
oolong tea
tea derived solely and exclusively from the moderately matured new shoots of varieties of the species
Camellia sinensis (Linnaeus) O. Kuntze, and produced by acceptable processes, notably withering, tumbling
and aeration (partial aeration/oxidization), enzyme inactivation, shaping/rolling and drying, which is
known to be suitable for consumption as a beverage
Note 1 to entry: Oolong tea can be categorized according to the degree of aeration into three main classifications: light
aeration/oxidization, medium aeration/oxidization and high aeration/oxidization.
[SOURCE: ISO 20716:2022, 3.1, modified — Note 2 to entry deleted.]
3.7
yellow tea
tea derived solely and exclusively, and produced by acceptable processes, notably enzyme inactivation,
rolling/shaping, yellowing and drying, from the bud or bud and the tender shoots of varieties of the species
Camellia sinensis (L.) O. Kuntze, known to be suitable for making tea for consumption as a beverage
[SOURCE: ISO 20715:2023, 3.16]
4  Principal components statistical and principle of Fisher’s discrimination method
According to ISO 20715, teas are divided into black tea, green tea, white tea, oolong (blue) tea, dark tea
and yellow tea. Different types of teas have special processing techniques. These techniques mainly affect
the aeration/oxidation degree and further affect the content changes of compositions, especially catechins
in fresh tea shoots, which affect the final sensory quality of the tea. Chemical analysis of tea is based on
the determination of characteristic compositions by ISO 14502-2 and ISO 19563, with catechins, caffeine
1) Under preparation. Stage at the time of publication: ISO/DIS 20680:2025.

ISO/TS 5617:2025(en)
and theanine as the major factors after the principal components analysis. The data used are pooled from
hundreds of test samples of six tea types worldwide. Then the principal components analysis with software
is applied and several discriminant factors are extracted that reflect differences among the six tea types.
Finally, the classic Fisher’s discriminant methods are applied to establish the discriminant formulae
to identify the tea type by step-by-step discrimination. The discriminant factors of the unknown tea are
[8][9]
determined and put into the discriminant formulae, and then its type is identified.
The oxidation level of fresh tea leaves, key processing steps and characteristics of the six tea types are given
in Annex B.
5  Reagents
Use only analytical grade reagents, unless otherwise specified.
5.1  Reagents  of  catechins  and  caffeine  determination, conforming to the requirements of
ISO 14502-2:2005, Clause 4.
5.2  Reagents of theanine determination, conforming to the requirements of ISO 19563:2017, Clause 5.
6  Apparatus
The usual laboratory apparatus and, in particular, the following shall be used.
6.1  Apparatus of sampling, conforming to the requirements of ISO 1839:1980, Clause 3.
6.2  Apparatus of preparation of ground sample, conforming to the requirements of ISO 1572:1980,
Clause 5.
6.3  Apparatus of determination of loss in mass, conforming to the requirements of ISO 1573:1980,
Clause 4.
6.4  Apparatus of catechins and caffeine determination, conforming to the requirements of
ISO 14502-2:2005, Clause 5.
6.5  Apparatus of theanine determination, conforming to the requirements of ISO 19563:2017, Clause 6.
7  Sampling
Teas received for type identification shall be “real” teas with regular sensory quality.
Sampling should be taken in accordance with ISO 1839.
8  Preparation of testing samples
Grind the test samples in accordance with ISO 1572:1980. Store the test samples in well-sealed containers in
a cool environment and protect them from light.
9  Quantification of the characteristic compositions in the unknown-type tea
9.1  Determination of dry matter content
Calculate the dry matter content from the moisture content in accordance with ISO 1573.

ISO/TS 5617:2025(en)
9.2  Determination of catechins and caffeine content
Quantify epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), epicatechin
(EC), catechin ((+)−C) and caffeine from the dry matter content (see 9.1) with individual catechins and the
caffeine standard curve determined on a portion of the test sample in accordance with ISO 14502-2.
Calculate the total catechins content by summation of the individual catechins (EGCG + ECG + EGC + EC +
((+)−C) in accordance with ISO 14502-2.
9.3  Determination of theanine content
Quantify theanine from the dry matter content (see 9.1) with i
...