Water Activity: Its significance to food safety and its accurate measurement

This short monograph consists of an introduction to the concept of water activity, a brief consideration of its significance to food safety, and a review of the various methods and instruments available for its measurement, including consideration of their utility and limitations. Water is a major constituent of foodstuffs and its measurement is therefore of considerable importance – not just for organoleptic reasons, but more importantly for microbiological food safety. Micro-organisms have narrowly-defined environmental requirements, including water levels, so foodstuffs with less than the required minimum for a particular organism will not support its growth. Therefore, if the Aw of a food is known, its likely microbiological status can be predicted: it is also possible to modify foods to an acceptable Aw. This, combined with other preservation methods, offers considerable scope for prolonging shelf life and generally improving microbiological food safety. Although increasing automation of existing methods has taken place since the review was originally prepared as part of a degree course in Food Science at South Bank University almost twenty years ago, the basic principles remain unchanged, and it should prove useful to modern-day Food Science students – in particular, its comprehensive reference and bibliography sections, which reflect the fact that the treatise was prepared from a total of more than eighty source documents.