Why do temperature differences also produce differences in the Aw value?

When you are responsible for the quality and shelf life of food, pharmaceutical, cosmetic or animal feed products, the Aw value (water activity) is of crucial importance because it indicates the likelihood of mould and bacterial growth. However, merely measuring and reading the Aw values is not enough to guarantee quality and shelf life. That is because there is another important factor. We would like to explain exactly what that it is and what you can do about it so that you can be certain.

Temperature determines Aw value

As well as measuring the Aw value (water activity) in a product, the temperature at which you take the measurement is critical if you are to guarantee the quality and shelf life of your products. This is because the extent to which the free water is available changes as the temperature rises or falls.
Imagine that the temperature is higher one day than the next (e.g. because it is warm outside and the temperature in your laboratory rises accordingly). The Aw value could be lower and it would appear that your products have a different shelf life than the ones measured on a cold day. What is truth?


Guarantee of quality and shelf life

If you’re a quality assurance or R&D employee, you don’t want these uncertainties, so it is vital that whenever and wherever you take the Aw readings, you do so at the same temperature. This applies whether you are in a factory, an office or another laboratory, or whether it’s a harsh winter or sweltering summer…. The temperature at the time of measurement must always be the same if you are to guarantee the quality and shelf life of your products. You will also minimise the likelihood of not being able to deliver products, or even worse, having to recall them. It is also a fact that for many products, there is a European requirement stating that the Aw value must always be measured at the same temperature (for meat products, for example, this is 25 degrees Celsius). And there is a good reason for that!


About the Aw value

The Aw value (water activity) is the amount of free water contained in a product. This can be used to establish the risk of mould and bacterial growth. Mould and bacterial growth can occur at an Aw value of 0.6 Aw or higher. As well as being important in the food industry, the Aw value is also a key parameter in the pharmaceutical, cosmetic and feed industries. It is measured with special Aw meters. Novasina Aw meters are popular because of their high accuracy and the temperature stability of the measuring chamber. The latter is important because, as we have seen, we need to be sure that the temperature is the same everywhere.


Insight through facts

The reason we are explaining this is that we’d rather gain insights from facts rather than relying on guesswork or half-truths. We love explaining these facts during the Aw symposia and webinars that we hold regularly. Please contact us for individual advice.


Feel free to ask us your question!

Do you have a question or would you like to request a quote? Please contact us by phone or send us an e-mail.

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