then be more important. Nevertheless, reactions involving water, like the
various kinds of enzyme-catalyzed hydrolysis, will all go to zero rate as
aw?0, irrespective of other considerations. The rate of a reaction in which
water is produced should increase asawdecreases, but the author is not
aware of unequivocal proof for such a situation in a food.
- Diffusivity. The rate of a bimolecular reaction may decrease if the
diffusion rate of the reactants decreases. In Section 8.4.1 diffusivity is
discussed, but we need to consider two other aspects. First, even ifDeffis a
FIGURE8.10 Relative rate of some reactions occurring in foods plotted against the
water activity (aw) at which the food was stored.