Spray drying is the most common method of dehydrating milk and milk products. It involves rapid removal of moisture, leading to the formation of amorphous lactose, which forms a continuous matrix in which proteins, fat globules, and air cells disperse. Spray-drying Packaging and the Shelf Life of Milk Powders technology in combination with other unit processes plays an important role in responding to market demands for powders with a wide range of functional properties. Spraydrying technology involves the transformation of the milk emulsion into a great number of small droplets that are exposed to a fast current of hot air as they fall into the spray chamber. As water is evaporated from the droplets they become powder particles. 

The quality of food powders is based on a variety of properties, depending on the specific application. In general, the final moisture content, insolubility index, dispersability index, free fat, rheological properties, and bulk density are of primary importance. These characteristics depend on drying parameters (type of spray dryers, nozzles/wheels, pressure, agglomeration, and thermodynamic conditions of the air: temperature, relative humidity, and velocity) and characteristics of the concentrate before drying (composition/physicochemical characteristics, viscosity, thermosensibility, and availability of water). 

The insolubility index is of primary importance for the quality of instant powders. Insoluble material is formed during spray drying of concentrated milk. The actual amount depends on the temperature and moisture content during the drying period. An important quality attribute of milk powder is the bulk density. It is obviously of considerable interest from an economic point of view because it in: uences the cost of storage, packaging, and transport.