The basic composition of any infant formula consists of:

The proportion, the quality and the processing of these elements determine the overall quality of the food. Since an infant formula may be the only source of nutrition of a new born infant, the choice of these criteria is vital.

Production of Infant Formula/Baby Food mix
In general, dried infant formula can be produced using either a “dry mix” or a "wet mix" process. Each type of the processes has its specific advantages and disadvantages.

The “dry mix” process
Advantages:

  • The lack of water involved in the process makes it safer from a microbiological point of view, as no growth can be expected. However, the microbiological quality of the final dry mixed powder will be no better than what was used to form the 'mix'.
  • A much smaller investment, as less equipment and thereby, a smaller building is needed. The costs for energy and maintenance will also be considerably lower.

Disadvantages:

  • It does not allow incorporating lipids, which means that the ingredients should already contain them.
  • No heat treatment is included. Thereby the physical and microbiological quality is defined by the quality of the raw materials used, and how the actual dry mixing is performed.
  • Physical powder properties such as wet ability and solubility will be defined by the properties of the single ingredients, unless a rewet agglomeration process follows the mixing and that adds to the investment and manufacturing costs. 
  • The different ingredients have different densities and will therefore segregate during canning and transportation. In other words, the product can get an inhomogeneous appearance and composition, which can be vital for the end-user.

Wet mixer from GEA Niro
Wet mixer from GEA Niro
The wet mix process
In the 'wet mix' process the situation is different. All quality aspects during wet mixing, concentration by evaporation and spray drying can be controlled to a higher degree resulting in better quality of the powder in terms of microbiology, physical and chemical properties.

Especially the possibility of heat treatment of the premix, either before or after the evaporation, is extremely important. Obviously, the investment as well as production costs become higher with this process.

The 'wet mix' process is, however, the most widely used, sometimes combined by adding some of the dry nutrients (e.g. vitamins, trace elements or carbohydrates) after the drying process, and each one of the major producers has their own way of preparing the 'wet mix' before final evaporation and/or drying.

Vacuum mixer from GEA Niro
Vacuum mixer from GEA Niro
Evaporation
The raw materials used in the different formulations are often mixed to lower solids content than optimal for spray drying. This is because the dissolving of the powdered materials is better at lower solids. Concentration by use of a falling film evaporator is usually done before the final drying, since it is cheaper to remove water by evaporation, as by spray drying.

Heat Treatment of Baby Food / Infant formula
The ever increasing focus on a hygienic production of an infant formula has made a high-heat heat treatment of the concentrate necessary.

Depending on product composition, this heat treatment is done either before the evaporation or after. Direct steam injection is used up to 100-140° C in fractions of seconds, followed by a flash cooling to 80 C°. The SANIHEAT equipment as developed by GEA Niro (patent pending), is used.

Spray Drying
The drying system typically consists of:

  • one or several high pressure nozzles or a rotary atomizer wheel for the atomization of the concentrate
  • a drying chamber/tower
  • an integrated fluid bed for secondary drying
  • an external VIBRO-FLUIDIZER™
  • one or several cyclone(s) and/or bag filter(s) as an air/powder separation system 
  • a fines return system to improve the agglomeration

Drying Parameters
In order to improve the production efficiency the drying temperatures and solids content of the concentrate are selected to be as high as possible. The product composition, however, is a decisive factor as to what parameters can be selected. Generally it can be mentioned that:

  • The drying efficiency and capacity of a spray dryer is increased by increasing the difference between the drying air and exhaust air temperature. 
  • High ambient air humidity requires a lower spray drying temperature or a dehumidification of the air, which obviously increases the production costs.

Powder Structure
Until few years ago, most infant formula was dried in a TALL FORM DRYER™ or a COMPACT DRYER™. Both dryers produce non-agglomerated and agglomerated powders. However, to a great extent infant formula sold today are marketed as agglomerated powders, since the agglomeration improves the reconstitution properties.

It is therefore important that the degree of agglomeration and the compactness of the agglomerates can be controlled. This is achieved in the Multi-Stage Dryer MSD™.

Finished Powder Conveying System
The final product from the spray dryer is conveyed to a silo system via a positive pressure dense phase conveying system. From the bottom of each silo, the product is conveyed to either a blending area for mixing with other powders or to the bag or can filling line by vacuum conveying. Normally the powder is packed in an N2 atmosphere to prevent oxidation of the milk fat or vegetable (polyunsaturated) oil.

To make things simpler the powder from the dryer can fall by gravity into a hopper and from the hopper direct to the bagging or can filling line. Which solution to chose, depends on the overall approach to logistics, capacity and investment.