Automatic Control of the Drying Process of Biological Materials using Optical Sensors to acquire Surface Temperature, Color and Shape

摘要

Improving drying processes necessitates the knowledge of changes the product is undergoing during drying in order to find significant phases. To gain this information online observation of the drying process is inevitable. Quality of heat sensitive products like fruits and vegetables significantly depends on the drying conditions. It is vital to insure that those products are not exposed to temperatures exceeding certain critical values as this may lead to the degradation of the product. This necessitates the optimization of the drying process parameters by means of product temperature measurement and control. Color is one of the most important quality criteria of food products. It does not only influence its subjective appreciation by the consumerbut it can also be used for the determination of quantitative quality criteria, which depend on the drying process. The degree of shrinkage is another value directly related to the quality of the drying process. Effect of air temperature level, air velocity, dew point temperature and control strategy on quality and product temperature were investigated. The paper gives a synopsis of the automatic control system as well as the techniques of online measurement and quantification methods for color and shape.