How to Measure Moisture Content in Food Products

food moisture content

Measuring moisture content to improve food quality 

Water plays an essential role in food production. As well as being a key ingredient, it is used for process heating and cooling, equipment washdown, steam sterilization, product rehydration, and dilution.

However, for a large number of food products, moisture can be detrimental to quality, shelf life and food safety, causing microbial contamination and changes in texture, appearance and taste. Foods such as cheese, pasta, rice and cereals are typical examples. For these products, moisture must either be removed or reduced to avoid contamination and preserve product integrity. 

Reducing the moisture content of food products is generally achieved using heating (drying), freeze-drying, freeze-concentration or osmotic concentration. Dehumidification is also being used to protect foodstuffs during storage and distribution. 

Efficiency and safety throughout each process depends on the ability to measure the moisture in the product or the production environment accurately and consistently. Precise moisture measurement also offers a benefit in helping to optimize the performance of energy-hungry dryers and dehumidifiers – this is something that is becoming increasingly critical as industrial energy prices continue to rise. 

Understanding the relationship between water content and food safety 

Water activity (aw), or equilibrium relative humidity (ERH), is a measurement of the water vapor pressure, which is generated by the free water present in a hygroscopic product. Put more simply, it is a measurement of the water available in a product or ingredient that could lead to microbial growth or, through migration, affect the quality of other ingredients. Note that water activity is not the same as moisture content, or the total amount of water within a product. If you would like to learn more about these differences, take a look at our blog post on Water Activity Measurement for Product Quality and Shelf-life.

The term ‘equilibrium relative humidity’ can be understood as the percentage relative humidity that is generated in equilibrium with a product sample in a closed system, held at a constant temperature.

ERH = 100 x aw

It is therefore possible to measure water activity using a relative humidity sensor or, preferably, a specialized water activity analyzer such as the Rotronic AW-Therm. 

If water activity needs to be reduced, this can be achieved by adding humectants such as sugar, salt or polymeric polyols, and freezing the product can preserve its quality.

Taking control of dryers and dehumidifiers 

Drying and dehydration are high-energy processes and dryers, in particular, are widely used in food production and for the pretreatment of compressed air and specialized gas systems. However, these processes can be energy efficient and work optimally. This is achieved by measuring water activity levels and moisture content of products and ingredients, then monitoring the output in real time. 

In particular, fitting a dew-point sensor to the outlet of these devices, as part of a control loop, can potentially allow drying time or dryer temperature to be reduced; it can also extend the operational life of desiccant materials. 

Centralizing moisture measurement 

As food production becomes more automated and digitization increases, so too does the need for effective monitoring of process equipment, from component level to integrated plant-wide monitoring systems matching the principles of Industry 4.0 (the rise of digital industrial technology). 

The latest generation of moisture, dew-point, relative humidity and water activity instruments are equipped with a choice of digital outputs, enabling them to be easily integrated into higher-level monitoring and control mechanisms. Our RMS continuous monitoring system, for example, offers a dedicated monitoring solution. This cloud-based or on-site platform incorporates an extensive range of dedicated hardware and software, compatible with products from other suppliers, and can be extended from just a few to several thousand measuring points. 

Regardless of the complexity and sophistication of measurement systems, the critical factor is to take control of water activity, relative humidity, dew point and other critical measurements, to ensure the quality, shelf life and safety of your food and drink products. 

Learn more about the products we recommend for the food and beverage industry; see our full range of moisture sensors. 

With almost 50 years’ experience in the development of innovative precision sensors, we are the application experts in dew-point and moisture measurements for all food and beverage applications. If you would like to discuss your requirements, please contact our team today.

Related Blog Post

Water Activity (aw) Measurement for Product Quality and Shelf Life

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Related Products

Dew-Point Transmitter for Industrial Dryers - SF52
Compressed Gas Dew Point Meter - Easidew PDP
Dryer Portable
Temperature-Stabilized Water Activity Analyzer - Rotronic AW-Therm

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