Drying food products - Principles

Drying is one of the main techniques for preserving agricultural and food products. It is also a process used in the manufacture of many food products, either as an integral part of processing or as an accessory (freezing, cooking, etc.). To understand the phenomena involved, it is essential to understand the equilibrium between air and product, and to master the kinetics of drying and product transformation.

This article begins by reviewing the physical principles of drying and the calculations that can be made for dryers, both in terms of treatment times (useful for sizing plants) and energy balances. An example of an energy balance for a spray-drying tower is given at 2.2.3 .

A second article [F 3 002] then describes the specific features of dryers used in the agri-food industry and the impact of the drying process on the quality of organic products. A final section will also be devoted to case studies:

• industrial corn drying ;

• spray drying of milk;

• drying of ente plums, a key stage in prune production;

• and an example of drying by boiling on a cylinder.

The drying of food products is the subject of two articles and one document:

• Drying of food products. Principles [F 3 000] ;

• Drying of food products. Applications and case studies [F 3 002] ;

• Drying of food products. Find out more [Doc. F 3 003].