Spray drying in the milk industry

Spray drying is a very common process for drying any kind of wet material. The technique is mostly used the food and pharmaceutical industry as part of the encapsulation and conservation process. Within the field of spray drying several different applications can be applied so ensure that no harm is done to the product. Thus, the milk industry has developed several processes for drying milk. One of these techniques is termed whey powder process and this technique is described below.

Whey powder process
Whey is another name for the milk plasma, which is a by product of cheese and casein production. Actually it is produced as part of the milk curdling process. It is used in several different food products such as Swiss cheese and cheddar. When using the whey powder process the drying is done by spray dryers also sometimes called flash dryers.

Spray drying the whey
The drying process is done by sending the wet material through an evaporator. The wet material is heated above the boiling point of water and at the same time a hot gas, usually air or nitrogen, is present. The process is fast and cheap and demands for no further processing afterwards. Usually amphipathic components are also added to ensure a even better atomization or in this example a finer whey powder can be achieved.

How spray drying works

Spray drying is the method of drying any wet material, called the liquid feed, by using a hot gas, usually just plain air as we breathe. However, some sensitive materials such as pharmaceuticals and ethanol demands for oxygen-free drying conditions. Here nitrogen gas is used because it is also very cheap.

The drying process
The drying process is usually a very fast one step process and thereby further handling of the material is eliminated. During the drying process the liquid feed is sent through an evaporator (sometimes also called an atomizer), which, as the name clearly states, atomises the liquid feed and produces extremely small droplets, which are further sent into the drying chamber. There are several different drying applications such as ddgs drying, Ring dryers, solids drying and Small scale dryers. Most often the technique is used in the food and pharmaceutical industry as part of the encapsulation process where the product is termed “the load”.

Example of the drying process
An example of a drying process is as follows: A substance (the load) is mixed and homogenized with an amphipathic (having both hydrophilic and hydrophobic properties) carrier. The mixing suspension is termed “the slurry” and is usually water. Then the slurry is sent into the drying chamber and heated to a temperature above the boiling point of water, thus enabling an efficient atomization. Note that the amphipathic properties of the carrier is extremely important for successfully producing these droplets.

The advantages of Spin Flash Dryers

One of the advantages of spin flash dryers is that the come in a huge size variety ranging from having a capacity profile of 1 kg per hour to up to 40 tons per hour. Thus, if one needs a small scale plant, for research purposes the spin flash dryers are ideal. Furthermore the small scale dryers are very easy to dismantle for cleaning purposes and are also easy to operate.

Suitable product to dry
Basically any wet material can be dried, these products being either of high viscosity or pastes. The important point is to select a proper speed and temperature among other factors.

Fast and cheap
Flash dryers and spin flash dryers are time efficient and therefore often also energy efficient. However, time is very often the most important factor in the preservation of products, because the longer the drying process takes the greater impact it has on the quality of the end product.

Additional features
As for any other spray dryer there are several additional features which can be incorporated onto the spin dryer. Most commonly a variety of filter can be applied for ensuring a finer end product. Also the filter enables a higher production percentage as particles being to big a left in the drying chamber for additional drying and powdering.