The amount of water present in foods is a factor that quantitatively demonstrates the composition of the food. In order to obtain information about the properties of water contained in food, it is necessary to know the water activity. This is because the relationship between the deterioration in the processing and storage of food products and the loss of flavor and quality is expressed only by water activity. Water activity determines how water in food products affects the structure of food, how some chemical reactions and microbiological activities occur and their degree.

In simple terms, water activity can be defined as the ratio of the water vapor pressure found in food products to the water vapor pressure of pure water at the same temperature.

In most fresh foods, water activity is above 0.99. Water activity is a factor that affects the shelf life, color, smell, texture and flavor of food products. Measuring water activity is therefore the most basic solution to reduce microbiological risks and improve food quality.

The average water activity values ​​of some food products are as follows: 0.2 in dried vegetables, 0.5 in chocolate, confectionery, honey, 0.7 in dried figs, 0.8 in jams and 0.9 in fresh meat, vegetables and fruits.

Even in foods with the same amount of water, there is a difference in durability. Therefore, water alone is not a decisive criterion for the durability of foods.

Within the framework of physical analysis, the determination of the distribution in water is carried out in the authorized laboratories. During these studies, standards and generally accepted test methods published by national and international organizations are followed.

The amount of water in food is an important indicator of the quality of food products. If the water content is high in some foods, the quality properties change and the food and food starts to deteriorate in a short time by enzymes and microorganisms. The amount of water contained in food serves as a solvent for many components.