Standard Method to determine the Water Activity (aw) in all food types at a constant temperature.

This method is intended as a general resource for microbiologists working in food and water laboratories in the UK, and specialist advice should be sought where required.

The aW of a food product can be used to predict microbial growth and to determine the microbial stability. Measuring the water activity in food indicates what ratio of water is available to allow microorganisms to grow.

The method describes how to measure aw from food using specialised equipment, conditions and how to perform calibration