Replacing Karl Fischer and other methods
As applications for water activity multiply, some begin to overlap with longer-established methods of measurement. Often, the investment in education and validation hinders water activity’s adoption to a new role, but in the long term, the speed, accuracy and usefulness of water activity brings significant returns.
Replacing Karl Fischer titration is the most obvious example, but perhaps the most misunderstood. Scientific investigation concludes that water activity is a far better predictor of product safety and stability than Karl Fischer water content. Even so, misconceptions continue – possibly because the relationship between moisture content and water activity can be counterintuitive.
A product with a high percentage of overall water content may have a very low water activity, or the other way around – a key factor when it comes to chemical and biological reaction rates.
Water activity does not provide the same information as Karl Fischer, but it does provide more useful information. The results will look different, but once understood, will provide better correlations to microbial safety, chemical stability, and physical properties. Not only that, water activity instruments generally don’t require extensive training and leave comparatively little opportunity for mistakes during testing.
Though water activity’s relationship to other measurements like HPLC or GC differs, many of the same advantages apply – less need for training, quicker results, more direct measurements, less risk of instrument misuse, and no need for dangerous chemicals.