counter current flow tunnel dryer
Puff-Drying
In this drying process foods are dried by explosion puff-drying. This
process is accomplished by exposing a relatively small piece of product to high
pressure and high temperature for a short time, after which the product is moved
to atmospheric pressure. This results in flash evaporation of water and allows
vapors from the interior parts of the product to escape. Products produced by Page 136 of 151
puff-drying have very high porosity with rapid rehydration characteristics. Puffdrying
is particularly effective for products with significant falling-rate drying
periods. The rapid moisture evaporation and resulting product porosity
contribute to rapid moisture removal during the final stages of drying. The puffdrying
process is accomplished most efficiently by using 2 cm cube shapes.
These pieces will dry rapidly and uniformly and will rehydrate within 15 minutes.