Instant foodstuffs is one very important part in Japan and other countries nowadays. Some of the meals are always freeze-dried ready meals. By converting the vacuum technology from liquid ring, some of the foods are able to achieve considerable energy saving and easily made. Maybe all other remaining vacuum systems with liquid ring vacuum pumps are to be replaced with modern dry vacuum technology that does not require operating fluids.
The systems to make freeze-dried foods usually have a chamber volume of about 30m3 and a cooling trap with 10 cubic meters, which means that a total volume of about 40m3 must be evacuated. In order to satisfy this, a total of 12 vacuum systems are usually used. They can be flexibly connected to the 16 freeze drying systems. The freeze drying process is divided into 3 parts: 1. when the fresh ingredients are deep-frozen at about -18°Celsius, the main drying process starts. During this process, the chamber is heated to a temperature of about 35°Celsius. The vacuum system evacuates the chamber to a pressure of 13 millibar. The ice sublimes into water vapor under this condition of temperature and pressure level.
However, there is still water bonded within the ingredients after the main drying process, and can negatively influence the life and quality of the shelf. Then, another process called subsequent drying works. It takes longer time in that bonded water in the product must be converted into water vapor first before it can be pumped out.
So in order to save energy and increase the efficiency in the field of making freeze-dried, vacuum pumps need to work better in the progress. Anyway, it is pleasing that everything is in the correct way with a fast speed.