*Water content
*Water activity
The water activity (aw) of a food is expressed as the ratio between the vapor pressure of the food itself, when in a completely undisturbed balance with the surrounding air media, and the vapor pressure of distilled water under identical conditions. It predicts whether water is likely to move from the food product into the cells of micro-organisms that may be present.
A water activity of 0.80 means the vapor pressure is 80 percent of that of pure water. The water activity increases with temperature. High water activity promotes the growth of microorganisms.
Products with a higher water activity are prone to degradation, and the development of mold and bacteria. Accuracy is very important when it comes to these products. At water activity 0.59 a product could be considered safe from the potential growth of bacteria and mold.
Controlling water activity in a powder product maintains proper product structure, texture, stability, density, and rehydration properties. Water activity is suitable measurement for predicting food safety and quality.
Water activity in food
