ABSTRACT
Water is an important constituent of all foods. Why water activity and not water content? In the middle of the 19th century, scientists began to discover the existence of a relationship between water in a food and its relative tendency to spoil. They also began to realize that the active water could be much more important to the stability (i.e., reactivity) of food than the total amount of water present. Scott [1] clearly identified that the water activity of a medium correlated well with the deterioration of food stability due to the growth of microorganisms. Thus, it is possible to develop generalized rules or limits for the stability of foods by using water activity. This was the main reason why food scientists started to emphasize water activity rather than total water content. Since then, the scientific community has explored the great significance of water activity in determining the physical, chemical, and sensory characteristics; effects of processing; and shelf-life prediction of foods.
