Insider Sample Prep Strategies for Faster, More Accurate Readings

Are you looking for faster and more accurate water activity readings? You're in luck. In this webinar, we'll cover some quick and simple ways to improve your food sample preparation to ensure you get fast, accurate, and endlessly repeatable water activity readings. 

What is water activity? 

As a quick reminder, water activity is defined as the energy status of water in a system. For more information on how water activity works, how it’s measured, and how the measurements can be used, please watch Water Activity 101: Mastering the Basics.

Temperature and exposure

One of the first variables to consider when improving your water activity readings is temperature. Managing your sample's temperature is vital due to the strong correlation between temperature and water activity levels. Since water activity levels of products are tested at all stages of production, it is essential to increase the instrument's temperature to match the temperature of the food sample or allow the sample to cool to match the instrument's temperature. Doing so will avoid issues with condensation or longer read times caused by the changes to the product as it comes to thermal equilibrium. 

Similarly, samples equilibrate with their surrounding environment, which can influence water activity and water content levels. Therefore, reducing sample exposure time is vital to improving accuracy and repeatable results. To ensure accurate water activity readings, samples should always be tested immediately or sealed in proper packaging until it’s time to test. 

Food sample preparation and optimization

Cleanliness is the first step to success in food sample preparation. Many people underestimate the need to ensure your testing area, cup, and instrument chamber is clean and free of crumbs or other contaminants. Using disposable sample cups is often ideal. 

Also, certain products require special food sample preparation to guarantee quick and accurate results. Here are some specific examples:

Coated products

When testing coated products, such as gel capsules or chocolate raisins, samples can be left intact or sliced. An intact sample will likely deliver a reading on the product's surface. However, to receive a water activity reading on the whole product, you should cut the product so the interior is also exposed. Then, cover the bottom of the sample cup with the sliced product to ensure an accurate reading. 

Emulsions

Emulsified products usually take longer to produce equilibrated readings, and multiple readings should be used to ensure accuracy. Mixing the sample with glass beads can also increase the surface area and reduce testing time.  

Multicomponent

Multicomponent products are non-homogenous products such as granola bars, protein bars, and cereal bars. The best way to get a representative sample of these types of products is to cut a sample, or multiple samples, from the middle of the product. It is often beneficial to then cut the sample into smaller pieces. For the most optimal readings, be sure to cover as much of the center of the sample cup as possible.

Glassy Samples

Glassy samples such as hard candy can take a long time to generate water activity readings. Breaking the product into smaller pieces will increase the surface area and allow quicker and more accurate reads. Be sure not to grind the product because doing so often changes water activity levels and can lead to inaccurate readings. 

Kibble and nuts

When testing for moisture content, products such as pet food, kibble, and nuts are often ground up. However, when looking to measure water activity, it is best to increase the surface area but leave the product's structure intact by breaking the product into chunks. By breaking the food samples into pieces and covering the bottom of the sample cup with the samples, you will improve the speed and accuracy of the test.

Meat snacks

As with other food sample preparation, grinding or shredding meat snacks can lead to inaccurate readings. Instead, chopping up the snacks and distributing the pieces over the bottom of the sample cups is optimal for testing. 

Utilizing these simple food sample preparation methods will significantly impact reading time and accurate and repeatable results.