National foreword

This British Standard is the UK implementation of ISO 21921:2025.

The UK participation in its preparation was entrusted to Technical Committee W/-, Miscellaneous Standards.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 October 2025.

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 has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely 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).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

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This document was prepared by Technical Committee ISO/TC 93, Starch (including derivatives and by-products).

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.

Introduction

Starch consists mainly of amylose and amylopectin. Amylose is a linear molecule of α-D-glucopyranosyl units linked by (1-4)-α-linkages. Amylopectin is a highly branched polymer of α-D-glucopyranosyl units linked by (1-4)-α-linkages and by (1-6)-α- linkages that constitute the branch points. In general, each glucose unit possesses a maximum of three hydroxyls that can undergo chemical substitution. A fourth substitution is also possible if that at carbon four (4) is not involved in a glycosidic bond. Several methods of starch modification exist and are applied to improve starch functionality. The most common sources of native starch used in these modifications are various roots, tubers, cereals and legumes.

Oxidation, a form of chemical modification, involves the deliberate introduction of carboxyl groups in the starch molecule. A common method of starch oxidation is the treatment of native starch with sodium hypochlorite. Once oxidized, starch can additionally be subjected to acid, alkali, enzyme, or bleaching treatment (FAO/WHO 2016).

Starch is a widely applied industrial additive, e.g., in the food industry, where it is utilised as emulsifiers, stabilizers, binders and or thickeners.

1 Scope

This document specifies the physical, chemical and microbiological requirements and test methods for oxidized starch in food applications.

2 Normative references

3 Terms and definitions

4 Requirements

4.1 Physical indexes

4.2 Chemical indexes

4.3 Contaminant limits

4.4 Microbiological limit

5 Test methods

5.1 Reagents

5.2 Iodine stain

5.3 pH

5.4 Copper reduction

5.5 Carboxyl group

6 Marking, packaging, transport and storage requirements

6.1 Marking

6.2 Packaging

6.3 Transport

6.4 Storage

Bibliography

BS ISO 21921:2025

Oxidized starch in food applications. Specifications and test methods

Current

Published:

31 Oct 2025