Alternative Methods

Isotherm Methods

Prominent scientists have long understood that the key to decoding the influence of water on shelf life, physical, and chemical recations is the moisture sorption isotherm.

1. Desiccators

Unfortunately, these same scientists knew only one way to make sorption isotherms:

      A. Obtain a large room that has a constant temperature, and lots of shelves

      B. Acquire scores of desiccators

      C. Mix various salt solutions of known water activity, and put them in the desiccators

      D. Prepare and weigh samples

      E. Place samples in desiccators, and wait until they stop changing weight

      F. Use final weight and humidity to construct product isotherm

This method is accurate, but yields poor data resolution and can take months.   Another problem is that high water activity samples tend to mold before finishing the equilibration process. 

2. Micro-balance Instruments

In the 1990's, a new class of instruments for automatically measuring moisture sorption emerged.  Most featured microbalances which measured tiny changes in weight as the product equilibrated at a humidity that the user could control.  These instruments represented a significant step forward by automating the process of monitoring vapor sorption.  However, they were also expensive, complex, and only worked on tiny samples.

See the AquaLab VSA, an instrument that combines simplicity, control, and affordability

Read about 5 ways isotherms can be used to improve quality

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