It is well known that moisture content, water activity and water distribution have a strong effect on the perception of crispness and on the mechanical signatures of dry, brittle, cellular foods such as biscuits. Food crispness has a sigmoid relationship with water content and activity (Heidenreich et al., 2004 and Peleg, 1994).
To compare the crispness behaviour of the different biscuits, the first step was to determine whether the moisture content and water activity could affect the sensory appreciation of crispness. The moisture and water activity values of the biscuits are shown in Table 3. The moisture contents ranged from 2.81 to 4.53 g water/100 g product and the aw values from 0.12 to 0.24. These low values ensure being in the initial part of the moisture–water activity curves (plateau), where crispness is independent of the water activity