How to Measure Water Activity In One Minute

METER Group’s lead food scientist and R&D lab manager discuss the breakthroughs that made 1-minute water activity readings possible – and if they’re truly dependable.

The ability to measure water activity has improved a lot over the years, with Meter's newest technology leading the industry with its groundbreaking ability to measure water activity in just one minute. Read on to learn more about the history of measuring water activity and how speed plays a crucial role in reducing uncertainty and leads to substantial positive impacts. 


The History and the Science of Water Activity Readings

The first water activity instruments were made in the 1960s and took about 60 minutes to produce a reading. Technology changed drastically over the following decades, and five-minute readings were possible by the late 1980s—though these came with their challenges. Finally, in 2020, Meter raised the bar when they made one-minute water activity readings possible. 

Considering the complex nature of measuring water activity, improvements in water activity readings are impressive. For example, from a physics perspective, several first-order processes occur in water activity, each with a different time constant, including the sample and its temperature and water vapor, the chamber temperature and vapor pressure, and the humidity of the sensor. The time constants are different for each of these items, but they also differ by product and change under varying conditions. Other challenges, backed up by recent testing, with first-order modeling include long run times and inconsistent results.

Second-order modeling is a more complex modeling process developed by physicists that uses strategies from predicting environmental modeling and requires samples to be identified to use the correct coefficients and requires three readings of a specific sample to start creating the model. 

Figure 1: Instruments that allow second-order modeling are faster and more accurate.

One-minute Readings and Reducing Uncertainty

One-minute water activity readings are possible through Meter products because of a handful of factors, including:

Meter's "normal" readings are typically as fast as competitors' "fast" readings

Meter has eliminated materials and surfaces on products that adsorb water

We already have accurate instruments and sensors where second-order modeling can be applied.

With this in mind, inherent variability contributes more to uncertainty than accuracy. Therefore, the best way to reduce uncertainty in water activity readings is to do more readings. For example, it is significantly more effective in reducing uncertainty to take ten one-minute readings instead of one 10-minute readin

Figure 2 - The best way to reduce uncertainty is to take more water activity readings.

Positive Impacts and Real-Life Examples

The most significant source of water activity uncertainty in food production is not taking enough readings—a challenge often directly related to time constraints. Fast water activity readings—specifically one-minute water activity readings—solve this problem and lead to other positive outcomes. These include setting up more robust testing protocols, making faster decisions on the production line, eliminating bottlenecks, optimizing logistics, and clearing shipments at up to 5x previous speeds. 

But don't just take our word for it. The real-life industry examples speak for themselves. For example, a well-known cured meat manufacturer reported that utilizing one-minute water activity readings helped them clear their ovens and cure rooms in a fraction of the time. They also reported a 40 percent increase in production and over $1 million in savings in planned investment to scale operations. An oven-baked oat bar company and sunflower seed producer reported similar results, including drastically saving time on run times, reducing lost batches and unnecessary rework, reducing batch release delays, and improved knowledge of when to package the product.

Figure 3 - Fast water activity readings can have significant positive business impacts.

Speed Is the Key

The speed of one-minute water activity readings is a game-changer. Because moisture issues always come with a cost, gaining greater control over your production process is invaluable. It can often lead to six- to seven-figure increases in yields (not to mention increased consistency and quality), making fast water activity readings a worthwhile venture for manufacturers of shelf-stable, intermediate-moisture foods. 

For more details on the science and technology behind water activity and specific food and product data from our competitor study, please watch the entire webinar. 

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