Water Activity Analysis

Water activity is related to energy. This value is the ratio between the food's own vapor pressure when it is in completely undisturbed equilibrium with the surrounding air environment. This measurement is directly related to the microbial susceptibility of food products and is associated with many reactions in foods that end shelf life.

For a cheap ingredient, water can cause many costly problems such as microbial growth, mold, tissue loss, caking and clumping, rancidity, loss of vitamins. The best way to understand the water in a product is to measure its water activity.

If the corner of a sponge is submerged in a glass of water, the water will move from the glass to the sponge. Water activity is the force that causes water to enter the sponge. Water in a sponge has a lower vapor pressure, lower freezing point, and higher boiling point than water in a glass.

The energy of water can be reduced by diluting it with solutes. These are called osmotic effects. This also reduces water activity, as work is required to return the water to its pure, free state. The total change in energy is the sum of the matrix and osmotic effects.

If a sample is placed in a sealed container, the relative humidity of the air in the headspace is equalized with the water activity of the sample. To know the water activity, the relative humidity of the headspace is measured.

Water activity can be measured with hygrometers and capacitance sensors. Many modern devices use electrical capacitance or resistance hygrometer sensors to measure the humidity in the headspace above the water. Accurate measurements require good temperature control or measurement. Capacitance sensors have a simple design and are often used in relatively inexpensive water activity meters.

The water activity of a food is the ratio between the vapor pressure of the food itself when it is in completely undisturbed equilibrium with the surrounding air environment and the vapor pressure of distilled water under the same conditions. A water activity of 0,80 means that the vapor pressure is 80 percent of the pure water vapor pressure. Water activity increases with temperature. The moisture status of a product can be measured as equilibrium relative humidity expressed as a percentage or water activity expressed as a decimal.

Our organization also provides water activity analysis services with its trained and expert staff and advanced technological equipment, among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors.