How to Measure Water Activity Meters for Food

Water activity in food is a key measure of its resistance to storage and safe transport and marketing. Along with food's increasingly stringent storage and quality control, one of the most critical parameters is water control. Fresh food that has yet to be measured for specific water content is prone to poor taste, spoilage and other problems during storage due to water problems.

Therefore, water activity plays a crucial role in ensuring the stability and quality of food. Let's find out what is water activity? Why is it so important? How do we measure the water activity of food?

What is Water Activity?

Water Activity (abbreviated aw) is the relative amount of water available in a food or other material. It is an important measure of water availability in a material and is usually expressed as a value between 0 and 1. Higher water activity indicates that the more water available in the material, the greater the potential for microbial growth (e.g. bacteria, yeast and moulds).

Factors affecting water activity include:

1. Temperature: an increase in temperature usually increases water activity.

2. Solute concentration: the presence of solutes (e.g., salt, sugar, etc.) decreases water activity.

3. The structure of the substance: e.g. how food is processed and stored.

How do we measure water activity for food?

There are several commonly used measurement methods to measure the water activity of food:

1. Water activity meter for food

A water activity meter calculates water activity by measuring a sample's relative humidity and temperature. The sample is placed inside the instrument and the instrument automatically gives the water activity value (between 0 and 1).

2. Drying method:

Typical systems use a sealed temperature-controlled chamber. The sample is placed inside the chamber and sealed. Free water is allowed to escape into the air inside the chamber. It will remain there until all the free water has left the sample.

3. Chemical Method:

Water activity is deduced by using a chemical reagent to react with the water in the sample and measuring the results produced by the reaction. This method is usually less direct and accurate than a water activity meter.

The role of the water activity meter

By measuring water activity, it is possible to predict which microorganisms will likely be the source of spoilage. In addition to affecting microbial spoilage, water activity affects the activity of enzymes and vitamins in foods. It also affects colour, taste and aroma.

Water activity meters are an essential tool for industries that require precise control of water content. These instruments measure a sample's equilibrium relative humidity (ERH) to understand its water activity level.

By accurately measuring water activity, manufacturers can:

Extend shelf life: Controlling water activity helps prevent microbial growth and extends the shelf life of products.

Optimise production processes: real-time water activity monitoring allows manufacturers to adjust processing parameters to ensure optimum product quality and efficiency.