The removal of moisture from a typical food product will follow a series of drying rates, as illustrated in Figure 12.3. The initial removal of moisture (AB) occurs as the product and the water within the product experience a slight temperature increase. Following the initial stages of drying, significant reductions in moisture content will occur at a constant rate (BC) and at a constant product temperature. The constant-rate drying period occurs with the product at the wet bulb temperature of the air. In most situations, the constant-rate drying period will continue until the moisture content is reduced to the critical moisture content. At moisture contents below the critical moisture content, the rate of moisture removal decreases with time. One or more falling-rate drying periods (CE) will follow. The critical moisture content is well defined due to the abrupt change in the rate of moisture removal.