A treatment device for treating food products with conditioned air includes a housing with a product inlet and product outlet. The housing defines a treatment chamber. The device includes at least one conveyor means for conveying the products through the treatment chamber from the product inlet to the product outlet, an air-circulator for causing an air stream to flow through the treatment chamber, and an air-conditioning for conditioning the air stream. The air-conditioner includes a heater and a moisture-feeder. The treatment device is also provided with controllable air-discharger for discharging air from the treatment chamber. A control device controls the moisture content of the conditioned air in the treatment chamber within a range defined by a predetermined lower limit and a predefined upper limit.