As discussed in the previous chapter whey contains about 0.8% protein corresponding to 13% of the dry matter. These proteins are known as serum proteins or whey proteins. As the nutritive value is considered very high, and as human milk contains more whey proteins than cow's milk, numerous attempts have been made to separate these proteins from the whey, especially for use in baby food powders.

The most accepted and widely used process is ultrafiltration. This process is however considered well-known to the readers and is therefore not discussed here.
The solids content and the composition of the concentrate also known as retentate from the ultrafiltration can be varied to meet special requirements in the final product.

Commercially, whey proteins are available with three different protein contents: 35% WPC, 60% WPC, and 80% WPC.

If 100 kg of normal sweet whey with 6% solids is used, then approx. 20 kg of 35% WPC is discharged from the ultrafiltration module with a solids content of about 10%, which is increased by evaporation to 45% before the spray drying. Approx. 8 kg of 60% WPC is discharged with a solids content of about 15%, evaporated to 42% before the spray drying. High protein concentration results in high viscosity, and it is necessary to add water (diafiltration) during the final filtration, if 80% WPC is produced. 3 kg of 80% WPC is discharged with a solids content of about 28-30%. Due to the high protein content it is dried directly.

Whey protein concentrates can be used direct, together with ordinary milk concentrates, in formulas for baby food thus obtaining a product with a composition similar to mother's milk.

The whey protein concentrates can also be used in the production of cream cheese or other soft type cheeses or as filler (water binder) in sausages replacing the meat.
The drying of whey protein concentrates is easy, but to maintain a good solubility of the product, it is essential to use low outlet air temperatures to avoid denaturation, see Fig. 139. Two-stage drying is therefore recommended.

Fig. 139  Solubility of the final WPC product as a funtion of the air outlet temperature from the spray dryer

As the solids content of the concentrate is low due to the high protein content, the spray drying plants are always equipped with bag filters after the cyclones. However, as the filter fraction may not always have the same quality as the main product, the Tall-Form Dryer is often selected, as the special air outlet minimizes the cyclone fraction and consequently also the filter fraction. See page 75 and Fig. 140.

Fig. 140  Tall-form dryer for whey protein products (TFD)

The tendency today is to produce agglomerated instant whey proteins. Due to the lack of lactose as binder, especially in 80% WPC, the agglomeration is difficult. However, by selecting the Multi-Stage Dryer, see page 203, Fig. 85, it is possible to obtain a sufficient agglomeration. As the proteins are very hydrophilic, they will absorb water instantaneously at their first contact with water, which makes the dispersion difficult. By agglomeration and lecithination the water absorption is delayed just sufficiently to allow the powder to be dispersed in the water before the final dissolution.

The powder has the same applications as the concentrates, but does have the supreme advantage of an almost infinite keeping quality.