| 摘要 |
A method of cooling a moisture-containing foodstuff article is described, which involves placing the article in a chamber and evacuating the chamber to reduce the pressure in the chamber, whereby moisture evaporates from the article and the latent heat of the moisture is extracted from the article. In order to prevent damage to the article by a too-rapid evaporation, the evacuation is controlled in response to dimensional change (typically the height) of the article. The invention also includes a method of controlling the evacuation of the chamber by progressively opening a valve in the pumping system to reduce the impedance (and hence increase the pumping rate) of the pumping system. This progressive opening of the valve is however, subject to an over-riding control which may arrest the opening action or initiate closing of the valve in response to a detected dimensional change of the article. Apparatus for carrying out the method is also described including a vacuum chamber, a detection means arranged to detect changes in a dimension of the article being cooled, a transducer adapted to be operated by the detection means and an actuator controlled by the transducer and arranged to regulate the pressure within the chamber in response to control signals from the transducer. |
