In the current global context, the use of and demand for energyand the shortterm projections for bothhighlight the need to include these matters in industrial process engineering. Moreover, environmental implications such as global warming or air pollution have led to energy consumption becoming an issue that must be taken into account, not only by designing new unit operations but also by including modifications into the present systems. In this context, drying is among the oldest, most common and most diverse of all industrial operations (Mujumdar and Devahastin, 2000), with hot-air drying being one of the most widely used methods. In this technique, the moisture content reduction is achieved by changing the phase of water from liquid to vapor; this permits transport of the vapor from a solid or liquid/paste product to the surrounding gas medium, but implies a heavy energy demand (Lewicki and Michaluk, 2004). Moreover, as the thermal efficiency of the current industrial processes is low (25-50%), the amount of energy needed for the process is very high (Vega-Mercado et al., 2001) such that, today, drying operations utilize a very high proportion of the industrial energy production of developed countries (Mujumdar and Devahastin, 2000).The high temperatures used in hot-air drying may have negative effects on the quality aspects of some products, especially of colored or heat-sensitive components, and in these cases low-temperature drying methods should be considered to obtain high-quality products. A moisture reduction can be achieved by evaporation if the drying temperature is above freezing point, or by sublimation if the temperature used is below freezing point. Such low temperaturesespecially those below freezing pointreduce the kinetics of any degradation reactions and maintain the natural attributes, thus achieving high-quality dehydrated products. This is certainly true in the case of vacuum freeze-drying (VFD), which is commonly known as freeze-drying, but also in the case of atmospheric freeze-drying (AFD). The low temperatures also reduce the drying kinetics, but in VFD this is partially overcome by applying vacuum conditions that increase the temperature gradient between the 237 0 1 2 3 4 5 AIR+US AIR D e (10 -11 m 2 /s)