Wasseraktivität gemessen - Was nun?

Novasina AG
Mittwoch, 24.4.2019

Sie haben die Wasseraktivität gemessen - Was nun? 

Ja. Was nun ? Sie haben sich für ein Instrument und eine Messmethode zur Messung der Wasseraktivität entschieden. Es sieht einfach aus, Sie legen Ihre Messprobe in die Probeschale, legen diese ins Gerät und das Messgerät zeigt Ihnen einen Messwert an. Aber was machen Sie nun mit diesem Messwert? Was sagt uns der angezeigte Wert und ist er gut? Darauf haben wir die Antwort. 


Es ist uns ein Anliegen, dass Sie genau verstehen, worum es bei der Messung der Wasseraktivität geht, was zu beachten ist und was Ihnen hilft, die Probleme in Ihren Produkten effizient zu lösen. Um eine passende, langfristige Lösung zu finden müssen Sie verstehen, warum Sie die Wasseraktivität messen. In Kooperation mit Dr. Brady Carter, Spezialist im Bereich Wasseraktivität, helfen wir Ihnen mit diesem Video, ein fundiertes Grundwissen aufzubauen.  

Unbearbeiteter Volltext zum Beitrag: 
You Measured Water Activity, Now What? 
By Dr. Brady Carter 

You have a water activity instrument or maybe you are thinking about getting a water activity instrument, so you can generate a water activity value. The test seems pretty simple. You place a sample in the instrument, push the read button, the test runs and a water activity value appears on the screen. Great. You look down at the screen and the water activity reported is 0.720 at 25C. Now what? Is that good? What does it mean? Why is it useful? What can you do with it?

So to answer the question of the significance of a water activity test result, you must first know why you are measuring water activity. You may wonder what are the most common reasons? Well, one typical reason is because water activity needs to be entered into a data sheet and the data sheet won’t be complete without it and your day is not over until that data sheet is complete.

Another common motivation for measuring water activity is because someone says it needs to be measured. This may be a supervisor, the R&D group, or an inspector. You run the water activity test so you can keep your job.

What that really means, if we are being honest, is that when you ask someone why they are measuring water activity, the most common answer received would probably  be, I don’t know.

But did you know that water activity is a powerful tool that can improve shelf life, assure safety, and improve stability. For instance, did you know that each microorganism stops growing at a specific water activity, which is determined by how adept the organism is at lowering its own internal water activity. All pathogenic bacteria that can cause serious foodborne illnesses will not grow at a water activity less than 0.86. In fact, the growth of all microorganisms stops at water activities less than 0.60.

Knowing this information, you can make changes to your formulation to adjust water activity. For example, you might choose to add glycerin to your product, which will lower water activity without additional drying and without altering the flavor. An additive that lowers water activity is called a humectant and you can closely predict how much humectant you need to add to achieve a certain water activity using mathematical models setup in a spreadsheet.

Did you know that water activity controls moisture migration in multi-component products like snack cakes with cream filling? Knowing the water activity of the cake and the filling will tell you if moisture migration will occur. If they are at different water activity levels, you can also use a mathematical model in an excel spreadsheet to predict how much moisture migration will occur and what the final water activity and moisture content of the cake and filling will be.

Did you know that you can control the caking and clumping of powders using water activity? There is a unique critical water activity for each powder where caking and clumping will start. At water activities less than this critical value, the powders will stay free-flowing, but at water activities higher than the critical water activity, the powders will get sticky, resulting in caking and clumping. This critical water activity will decrease with an increase in storage temperature   and has a strong association with   transition.

Did you know that you can slow down rancidity and browning by controlling water activity? In general, as water activity increases, so does the reaction rate of most common degradative reactions. Knowing which reaction could impact your product and the rate of the reaction at a given water activity makes it possible to know the best by date for the product.

In fact, did you know that you can predict shelf life of your product just by knowing its water activity and temperature? While many factors influence shelf life, water activity and temperature play the largest role. While most shelf life models deal with just temperature effects, a new shelf life model has been created that can determine how long it will take for your product to go from acceptable to unacceptable based on both water activity and temperature.   

Finally, did you know that you can predict what type of packaging you need to effectively control water activity and extend shelf life? Moisture permeability of packaging determines what level of water activity change a product will experience under a given storage condition. Tools can be used to both predict the water activity change of a product in a given package or predict the type of packaging needed to minimize water activity change under both normal and abuse storage conditions

I’m sure you would agree that all these water activity applications have the potential to give you more control over the safety, quality and shelf life of your product and answers the original question of why measure water activity.

Now that you understand the value in measuring water activity, the next step is choosing a water activity supplier that can provide the high levels of both instrument and application support needed for optimal utilization of water activity.

Novasina fields an experienced support team that can provide instrument and application assistance worldwide through an extensive distributor network. Novasina was the first company to release a widely distributed water activity instrument back in 1966. This water activity meter utilized an electrolytic sensor just like the one used in Novasina instruments today, meaning they have 50 years of experience perfecting the sensor.

They are not only dedicated to superior water activity measurements, but also to understanding the science of water activity and providing their customers with the knowledge and training needed to fully utilize water activity testing. To that end, Novasina has begun a partnership with water activity scientist, Dr. Brady Carter, enabling them to further enhance their application capability and provide an unmatched level of water activity support.

So water activity can be more than just a number on the screen. In fact, considering all the critical stability factors it impacts, it should be the most important product release specification for shelf stable products. With that in mind, choosing a water activity supplier that can help you fully utilize your water activity testing results is critical. Regardless of whether you are searching for your first water activity meter, or you are looking to add to or replace an existing instrument, choosing Novasina gives you access to an unmatched level of knowledge and support.

We only briefly introduced the broad utility of water activity here, but if you are interested in learning more about the powerful applications mentioned earlier, Novasina is publishing additional educational videos. Please continue to visit the webpages of either Novasina or your local distributor to view additional videos in our ‘what to do with water activity series’.


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