Dehydration takes place when the water intake is exceeded by water loss. This process is the same for all organisms that have a high-water content inside their cell structure. Right after being harvested, fruits and vegetables will start to lose weight and dehydrate, since the moisture moves out of the cell and then evaporates into the air. The term for dehydration is either evaporation, when water turns from a liquid to a gas state, or sublimation, when it turns from a fixed state to a gas.

In open air, moisture just escapes, but inside an IQF tunnel, it will start to create ice and snow, when the air is saturated with moisture. This process is called precipitation. The effect of dehydration inside an IQF tunnel is the shrinkage and damage to the product's surface and an actual loss of the product, that turns out as snow.

As the air gets colder, it also gets dryer, and the IQF products will get more dehydrated since there is a strong link between temperature and dew point. A quick-freezing time will allow for lower dehydration since more sublimation generally happens before the surface of the product is crust frozen. Naturally, a smaller product, with more surface compared to weight and volume, will dehydrate more than a larger product.

If precipitation can be avoided, dehydration will be limited. The key is keeping the air inside the IQF tunnel saturated, so that it doesn't take up moisture from the products. Even if the air is saturated, dehydration needs to be avoided at all costs. An efficient crust freezing and a low infeed temperature inside the IQF tunnel represent a good start. The challenge is to optimize the settings for airflow and speed since too much might remove moisture, and too low will slow down the freezing time.

Having good aerodynamics and an even airflow inside the IQF tunnel reduces turbulence and, in consequence, lowers the precipitation (snow formation). The air inside the IQF tunnel should be kept moving because as soon as it stops it will start to precipitate and create snow. When the air moves through the coil, it gets colder and therefore has the tendency to precipitate. In order to avoid this, the airspeed could be accelerated after passing through the coil.

Freezer burns will decrease the value and quality of an IQF product. It can be protected with light surface water from washing before freezing, but the weight loss is still applicable. Traditional IQF tunnels have a 1.5 - 2% dehydration which can be measured as snow formation, but it can be reduced, in optimal conditions, to 0.3 - 0.5%. However, in a spiral freezer, dehydration can be up to 4%. In terms of financial loss, with a yearly production of 2.000.000 EUR, 20.000 EUR per year can be saved if dehydration is lowered by 1%.