If the ERH of the food or pharmaceutical product is below the values shown, the organism simply cannot grow.

The Regulatory Authorities which control medicinal products require solid oral dosage forms e.g. tablets and capsules, to be tested for the presence of micro-organisms. This test is called the Microbial Limit Test (MLT).

The MLT is performed in stability studies and is one of the parameters used to measure product shelf-life and determine the expiry date seen on each container.

Application of ERH (Water Activity) to microbiological control of pharmaceutical products has been recognised by the US Food and Drug Administration and covered by a new chapter in the USP <1112> “Application of Water Activity Determination to Nonsterile Pharmaceutical Products”.

ERH then could be used to replace the MLT in stability testing and Relequa provides the simple alternative to use in pharmaceutical product development and shelf life studies.

A detailed explanation of ERH can be found at http://www.lsbu.ac.uk/water/activity.html