ISO 13580:2005

Yogurt - Determination of total solids content (Reference method)

ISO 13580|IDF 151:2005 specifies a reference method for the determination of the total solids content of plain, flavoured, sweetened and fruit yogurts.

Yaourt — Détermination de la teneur totale en matières solides (Méthode de référence)

General Information

• Status: Published
• Publication Date: 12-May-2005
• ICS: 67.100.99 - Other milk products
• Technical Committee: ISO/TC 34/SC 5 - Milk and milk products
• Drafting Committee: ISO/TC 34/SC 5 - Milk and milk products
• Current Stage: 9093 - International Standard confirmed
• Start Date: 25-Nov-2022
• Completion Date: 30-Oct-2025

Overview

ISO 13580:2005 (IDF 151:2005) defines a reference method for determining the total solids content of yogurt - including plain, flavoured, sweetened and fruit yogurts. The standard describes sample preparation, apparatus, the zinc-oxide oven-drying procedure at 102 °C ± 2 °C, and the compensation for water loss due to neutralization by measuring titratable acidity. Results are reported as a percentage by mass to two decimal places.

Keywords: ISO 13580, total solids content, yogurt, reference method, zinc oxide, drying oven, titratable acidity

Key topics and technical requirements

• Scope: Applies to plain, flavoured, sweetened and fruit yogurts; sampling is referenced (ISO 707/IDF 50 recommended) but not part of the method.
• Principle: Evaporate water from a weighed test portion in the presence of zinc oxide and determine lactic acid (titratable acidity) to correct for water formed during neutralization.
• Reagents & purity: Zinc oxide, at least 99% purity; use analytical-grade reagents and demineralized water.
• Apparatus: Analytical balance (readability 0.1 mg), desiccator, well-ventilated drying oven (102 °C ± 2 °C), flat-bottom dishes (50–75 mm diameter), boiling/steam bath, homogenizer for fruit yogurts.
• Procedure highlights:
  • Pre-dry dish with ~2 g zinc oxide at 102 °C for ≥1 h, cool in desiccator, weigh.
  • Place 1 g test portion, add 5 mL water, mix with zinc oxide; pre-evaporate on boiling/steam bath (30 min), then oven-dry at 102 °C (initially 3 h), cool and weigh.
  • Repeat oven heating (1 h cycles) until change ≤1.0 mg; use the lowest mass for calculation.
  • Determine titratable acidity (ISO 11869) and apply a 0.1% correction factor for neutralization.
• Calculation: Total solids calculated from the difference between dish masses (empty, with sample, dried) and adjusted using measured acidity.
• Precision: Repeatability limit ≈ 0.28%, reproducibility limit ≈ 0.45% for the tested ranges.

Applications and who uses it

• Dairy laboratories and QC teams in yogurt manufacturing for product specification, formulation control and label compliance.
• Food technologists and R&D for formulation optimization (solids content affects texture and yield).
• Regulatory authorities and conformity assessment bodies verifying declared solids content.
• Contract testing labs offering standardized analyses for manufacturers and retailers.

Using ISO 13580 ensures reproducible, comparable total solids results across laboratories and supports quality control, product development and regulatory compliance in the dairy sector.

Related standards

• ISO 11869 - Yogurt: determination of titratable acidity (potentiometric method) - required for acidity correction.
• ISO 707 / IDF 50 - Sampling of milk and milk products (recommended).
• ISO 5725 - Precision of measurement methods (interlaboratory precision rules).
• IDF 151 - Equivalent IDF publication; method also published by AOAC International.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 13580
IDF
First edition
2005-05-01
Yogurt — Determination of total solids
content (Reference method)
Yaourt — Détermination de la teneur totale en matières solides
(Méthode de référence)
Reference numbers
IDF 151:2005(E)
©
ISO and IDF 2005
IDF 151:2005(E)
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ii © ISO and IDF 2005 – All rights reserved

IDF 151:2005(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Principle. 1
5 Reagents. 1
6 Apparatus. 2
7 Sampling. 2
8 Preparation of test sample. 2
8.1 Natural yogurt and flavoured, sweetened yogurt .2
8.2 Fruit yogurt. 2
9 Procedure. 3
9.1 Preparation of the dish. 3
9.2 Test portion. 3
9.3 Determination of total solids content . 3
9.4 Determination of lactic acid content . 3
10 Calculation and expression of results . 4
10.1 Calculation. 4
10.2 Expression of results. 4
11 Precision. 4
11.1 Interlaboratory test. 4
11.2 Repeatability. 4
11.3 Reproducibility. 4
12 Test report. 5
Annex A (informative) Interlaboratory test. 6
Bibliography . 7
IDF 151:2005(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 13580IDF 151 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5,
Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International.
It is being published jointly by ISO and IDF and separately by AOAC International.

iv © ISO and IDF 2005 – All rights reserved

IDF 151:2005(E)
Foreword
IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National
Committee in every member country. Every National Committee has the right to be represented on the IDF
Standing Committees carrying out the technical work. IDF collaborates with ISO and AOAC International in
the development of standard methods of analysis and sampling for milk and milk products.
Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the
National Committees for voting. Publication as an International Standard requires approval by at least 50 % of
the National Committees casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. IDF shall not be held responsible for identifying any or all such patent rights.
ISO 13580IDF 151 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5,
Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International.
It is being published jointly by ISO and IDF and separately by AOAC International.
All work was carried out by the Joint ISO/IDF/AOAC Action Team on Water, of the Standing Committee Main
components of milk, under the aegis of its project leader, Mrs M. Nicolas (FR).
This edition of ISO 13580IDF 151 cancels and replaces the first edition of IDF 151:1991.

INTERNATIONAL STANDARD
IDF 151:2005(E)
Yogurt — Determination of total solids content (Reference
method)
1 Scope
This International Standard specifies a reference method for the determination of the total solids content of
plain, flavoured, sweetened and fruit yogurts.
2 Normative references
The following referenced document is indispensable for the application 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.
1)
ISO 11869, Yogurt — Determination of titratable acidity — Potentiometric method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
total solids content
mass fraction of substances remaining after completion of the heating process specified
...