Water Activity Standards: A Review

Since water activity testing is critical to ensure quality and safety of manufactured products, it is common to find water activity instruments in most quality assurance laboratories. As with any laboratory test method, good laboratory practices require routine verification assessments for water activity to make sure the instrumentation is working properly. This can be accomplished by running tests on standards of known value and comparing the test results to the actual values. While this can be difficult for some common quality assurance tests that do not have independent standards, such as moisture content, water activity standards exist in the form of electrolytic (salt) solutions. These water activity standards are one of the most important tools available to laboratory personnel to provide them with confidence in their water activity testing results and facilitate troubleshooting. 

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The Shelf Life of Bakery Products Simplified with Water Activity

The baked snack industry is a constantly growing market valued a $440 billion. These products typically cover a range of textures, coors, and flavors, and it is critical that they remain safe while maintaining their expected texture and sensory properties. One of the most important factors influencing the quality and shelf life of bakery products in water activity. Water activity control can help prevent or minimize various degradative events such as rancidity, microbiological spoilage, staling, or changes in texture due to water migration. 

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Water Activity Test Time: It's the Sample, Not the Instrument

There can be an abundance of confusion with water activity instruments concerning test time. Some instruments claim a 5-minute test time while others offer fast or quick modes. The truth is that water activity test time is determined by the sample and not the instrument. Since water activity is an equilibrium measurement, a reading is not complete until vapor equilibrium has been achieved and this process cannot be sped up by an instrument (1). So, any claim to a specific test time is illogical and would only be true for select samples. The reality is that most types of samples require a minimum of 5 minutes or more to reach true equilibrium and test times that are faster than that are either using a prediction or the system uses end-of-test settings that are not stringent enough to achieve true vapor equilibrium. 

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Pharmaceutical Trends: Water Activity Measurement USP 922

Water activity has been broadly used in the pharmaceutical industry since the publication in 2006 of USP <1112>, an informational chapter on the application of water activity in pharma. While <1112> provided guidance for the utilization of water activity, it was not an official method.

Now USP has developed USP <922> Water Activity as an official method which will hopefully further facilitate its implementation as an integral part of a pharmaceutical quality program.

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The Role of Water Activity in Cannabis Quality and Safety

Cannabis-based products for both medicinal and recreational use are gaining in popularity and acceptance. However, if not handled properly, these products can pose a safety issue for consumers. Dried buds, extracted oils, or processed edibles with microbial contamination can result in allergic reactions, respiratory complications, or foodborne illnesses. From a quality standpoint, changes in efficacy and potency due to chemical reactions or structural loss can also result in poor product and lost revenue. Water activity is utilized as an effective tool in the food and pharmaceutical industries to maximize microbial, chemical, and physical stability. It provides this same safety and control to the cannabis market and it is important that cultivators and processors understand water activity and how to maximize its usefulness. Safety regulations for the cultivation and processing of cannabis-based products is currently handled at the state level, resulting in inconsistent recommendations. As a result, not all states currently require water activity testing of cannabis. However, based on its established relationship with common safety and quality modes of failure, it should be one of the most important analytical test run by anyone in the cannabis market. 

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Maintaining Green Coffee Quality Through Water Activity Control

The international coffee market is valued at $102 billion. It includes everything from freeze dried instant coffee to specialty blends carefully sourced from specific growing locations. Not surprisingly, the highest quality coffee comes at the highest price along with the highest quality expectations. Coffee beans are harvested as a coffee cherry that is then processed to remove the fleshy cherry covering to produce green coffee beans. These green coffee beans are the form in which the coffee is stored and transported. When it is time to produce coffee, the green beans are roasted to create the familiar roasted coffee beans that are purchased at a store or utilized at a coffee house. The roasted beans are ground and brewed to produce the familiar cup of coffee. Obviously, each of these steps provide their own challenges and each can impact the quality of the coffee produced. 

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Shelf Life Simplified: A Water Activity Based Approach

By Dr. Brady Carter


The shelf life of a product is defined as the practical time that it remains desirable to consumers. It dictates the radius of distribution for the product, how it must be stored, and its best by date. Failure to match this expected shelf life can result in customer complaints, product recalls, and tarnished reputation. Consequently, correctly determining the optimal production process and handling that maximizes the shelf life and then monitoring to make sure those conditions are met is the difference between profitability and lost revenue. However, correctly determining the shelf life of a product can be a challenging endeavor, often due to a lack of resources and clear guidelines for conducting shelf life testing. The shelf life simplified paradigm takes a pragmatic approach to shelf life determination by using the relationship between water activity and shelf life to guide the process.

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