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WATER ACTIVITY STANDARDS AND REGULATIONS

Water activity is an important quality control parameter in many industries, especially when product safety, microbial stability and shelf life need to be evaluated. For QC teams, the key point is simple: a water activity result is only useful if it is measured with a suitable method, a reliable instrument and proper calibration standards.

Why this matters in QC

Water activity is used to understand how much water is available in a product. This is different from moisture content, which only describes the total amount of water. For microbial growth, stability and product risk, the available water is often the more relevant parameter. This is why water activity is included in several recognized standard methods and regulatory frameworks.

Common water activity methods

Depending on the industry, different methods may apply. Examples include:

  • AOAC 978.18 for food applications
  • ISO 18787 as a general water activity method
  • ASTM D8196-18 for cannabis
  • USP <922> for pharmaceutical applications
  • MFLP_63 in Canada, which describes the use of Novasina instruments for water activity measurement

These methods define important requirements such as temperature control, resolution, accuracy, stability criteria and calibration with saturated salt standards.

Regulatory relevance

Water activity is also referenced in several regulatory contexts. It can be used as a monitoring tool for microbial control in food safety systems, as part of HACCP or HARPC concepts, and as a supporting parameter in pharmaceutical and cosmetic risk assessment.

For QC teams, this means water activity can help to:

  • evaluate microbial risk
  • support product release decisions
  • justify reduced microbial testing where applicable
  • monitor process consistency
  • support audit and documentation requirements

What to check in daily practice

When using water activity in QC, make sure that:

  • the correct method is selected for your industry
  • the instrument is suitable for the product type
  • temperature is controlled during measurement
  • calibration is performed with suitable salt standards
  • results are documented and traceable
  • the aw limits are defined based on product risk and application

Download the overview

We have prepared a short overview of common water activity standard methods and regulatory references. It gives QC teams a practical starting point to understand which methods and requirements may be relevant for their application.

Read as PDF