assuming condensation of an infinite number of layers from
the vapour phase onto the adsorbent surface. Xe is the
equilibrium moisture content, Xm represents the monolayer
moisture content, and CBET is an energy constant. It must be
noted that the BET model was originally derived with
reference to gas adsorption on crystalline surfaces. It is
based on the theory of a constant surface area and would
not be applicable to the analysis of the moisture sorption
behaviour of amorphous food involving structural changes
caused by water (Tong et al. 2008). It can therefore be
applied only if the analysis is limited to a certain aw at
which significant water absorption into the bulk and dissolution
of the material have not yet occurred. According to
Labuza and Altunakar (2007), the aw range applicable to the
BET model is between 0 and 0.55.