Mixing is one of the basic operations in mechanical processing engineering. In this way, at least two starting substances are combined into one substance that should be as homogeneous as possible.
The mixing process is commonly followed by de-aeration since, during the processing of liquid to highly-viscous products, pockets of air or gas often cause problems. Pockets of air, hence oxygen, can have negative effects on the product – such as oxidation, rancidity of fats or oils, discoloration or deterioration of aroma and taste for example – and, for materials that are to be coated, can lead to porous and pitted surfaces. In contrast, de-aerated products are usually more chemically stabile and more durable.