How is the Water Activity of Foods Determined?

The water activity (aw) of foods can be determined using various methods, including:

Electronic hygrometer: This instrument uses a sensor to measure the water vapor pressure of a food sample and calculates the water activity based on the measured values.

Dew point method: In this method, a sample is placed in a sealed container and the temperature inside the container is gradually lowered. The point at which dew forms on the surface of the sample is measured, which is used to calculate the water activity.

Psychrometry: This method involves measuring the relative humidity of the air surrounding a sample and the temperature of the sample. The water activity is then calculated based on these measurements.

Gravimetric method: In this method, a sample is weighed and then heated to remove all water. The sample is then weighed again to determine the amount of water lost, which is used to calculate the water activity.

The specific method used will depend on the equipment and resources available, as well as the type of food being tested.