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What is the Aw value or water activity?

Uitleg over aw waarde

Pedak has built up over 45 years of knowledge and experience in measuring Aw value (water activity) and we are only too happy to share it! Find out more about water activity in the following blog.

Aw value (water activity)

Aw value (water activity) measurement is carried out for controlling the quality of:

  • Meat / fish
  • Bread and pastries
  • Cheese / dairy
  • Processed food
  • Chocolate / sweets
  • Pharmaceutical products
  • Cosmetics
  • Pasta / dried products
  • Animal feed


What does the “water activity” parameter mean actually ?

1 Total water/moisture

The moisture content is the total amount of water – including chemically bound water – present in a food item, expressed as a percentage of the total weight.

2 Water activity (Aw value)

The relative moisture balance of a product; i.e. the “free” water present which allows microorganisms to grow. The measurement value taken gives us the “water activity” (Aw value) and ranges from 0.03 – 1.0 Aw.

Water is a basic ingredient found in food, pharmaceuticals and cosmetics. Monitoring the Aw value can be crucial for ensuring microbial safety during a product’s shelf life and consumption, as well as for guaranteeing an optimal production process.


Why measure Aw value?

Water activity, pH, temperature and other parameters correlate directly with the growth of microorganisms, with the Aw value and pH value being the two most significant ones. Free water that is available to fungi, yeasts and bacteria is behind their growth and even the production of toxins. It can cause chemical/biochemical reactions (e.g. Maillard reactions) that have a negative impact on the following product characteristics:

  • texture, flavour
  • colour
  • flavour
  • nutritional value
  • stability (shelf life)

These are just some of the main reasons why measuring water activity (Aw value) correctly is so important.

Each year we also share our knowledge at symposia. To find out more, watch the video of our online symposium.


Pedak is the exclusive distributor of Aw meters made by the Switzerland-based company Novasina.

Click here to see the range of Novasina Aw meters




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