ISO 18787-2017 PDF

Full title and description

ISO 18787:2017 — Foodstuffs — Determination of water activity. This international standard specifies principles and requirements for laboratory methods to determine the water activity (aw) of foods and animal feed, including measurement principles, limits of applicability and guidance on equipment and interlaboratory performance.

Abstract

ISO 18787:2017 establishes basic principles and specifies requirements for methods of determining water activity (aw) of food products for human consumption and animal feed within the measurement range 0 to 1. Measurement principles covered include dew‑point measurement and methods based on changes in electrical conductivity of an electrolyte or in the permittivity of a polymer. The standard also states exclusions (products stored below their freezing point, water‑in‑fat emulsions, crystalline products such as sugars or salts) and notes equipment adaptations for products containing volatile compounds; results of interlaboratory studies are provided in an annex.

General information

• Status: Published.
• Publication date: November 2017 (2017-11).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 67.050 (Food chemistry and analysis).
• Edition / version: Edition 1 (2017).
• Number of pages: 9 (ISO published version).

Scope

Specifies requirements and fundamental principles for laboratory determination of water activity in foodstuffs and animal feed across the measurement range 0–1. Methods described are principally based on (1) dew‑point measurement and (2) determination of changes in electrical conductivity of an electrolyte or in the permittivity of a polymer. The standard excludes products stored below their freezing point, products that are water‑in‑fat emulsions and crystalline products (e.g., sugars, salt, minerals). It also highlights that for samples containing volatile compounds (for example alcohols) equipment adaptations may be necessary, and it includes interlaboratory study results in Annex B.

Key topics and requirements

• Definition and importance of water activity (aw) in foods and feeds.
• Measurement principles: dew‑point hygrometry; electrolyte conductivity changes; polymer permittivity methods.
• Measurement range covered: 0 to 1 (dimensionless aw scale).
• Sample applicability and explicit exclusions (frozen products, water‑in‑fat emulsions, crystalline products).
• Instrumentation and equipment considerations, including adaptations for volatile compounds.
• Requirements for calibration, procedure reproducibility and reporting of results.
• Results from interlaboratory studies and guidance provided in Annex B.
• Replacement of ISO 21807:2004 (the earlier water activity standard).

Typical use and users

Used by food and feed manufacturers, quality control and analytical laboratories, research organisations, certification bodies and regulatory agencies to measure and control water activity for shelf‑life, safety (microbial stability) and formulation purposes. Laboratories use the standard to select appropriate measurement methods, document procedures and demonstrate traceable, reproducible results in product testing and R&D.

Related standards

Replaces ISO 21807:2004 (withdrawn). Related documents and regional/adopted versions (national adoptions, purchasing variants) exist from national standards bodies and technical committees dealing with food analysis (ISO/TC 34). For specific measurement techniques and instrument calibration, laboratories may also consult complementary standards and guidance from ISO/TC 34 and relevant national bodies.

Keywords

water activity; aw; foodstuffs; animal feed; dew‑point hygrometer; conductivity method; permittivity; quality control; shelf life; ISO 18787:2017.

FAQ

Q: What is this standard?

A: ISO 18787:2017 is an international standard that specifies principles and requirements for laboratory methods to determine the water activity (aw) of foods and animal feed.

Q: What does it cover?

A: It covers measurement principles (dew‑point, electrolyte conductivity change, polymer permittivity), the measurement range (0–1), applicability limits, equipment considerations (including for volatile compounds) and interlaboratory performance information in Annex B. It excludes products stored below freezing, water‑in‑fat emulsions and crystalline products like sugars or salts.

Q: Who typically uses it?

A: Food and feed manufacturers, QC/analytical laboratories, research organisations, certification bodies and regulators concerned with shelf life, microbial safety and product formulation use this standard.

Q: Is it current or superseded?

A: ISO 18787:2017 is the current ISO international standard for this subject (published November 2017) and it replaced ISO 21807:2004.

Q: Is it part of a series?

A: It is a standalone ISO standard developed under ISO/TC 34 (Food products) addressing a specific measurement—water activity—but it sits alongside other ISO and national standards and guidance on food analysis and quality control.

Q: What are the key keywords?

A: Water activity, aw, dew‑point hygrometry, conductivity method, permittivity, foodstuffs, animal feed, shelf life, quality control, ISO 18787:2017.