Fat-enriched whey has been produced for many years, especially in Europe where the product is used as animal feed. Addition of fat to the whey concentrate in the range of 26 to 50 % of the dry matter is normal. This product is then used directly or in a dry-mixing operation to make different calf milk replacers. The fat used is mainly a cheap sort such as lard or tallow. Precautions against the presence of polyunsaturated fat acids should be taken by addition of antioxidants to prevent fires in the spray dryer.
Processing of fat-enriched whey
- Sweet whey of good quality with normal content of whey proteins should be used. The pH should not be lower than 6.3-6.4 in the raw whey. It is possible to neutralize with Mg(OH)2 to improve the fat emulsion stability and to stabilize salts of citrates, phosphates, and lactates.
- Immediately after the cheese process, the whey must be pasteurized at 72 °C for 15 sec. and cooled to 4-5 °C for storage.
- Before evaporation the whey is pasteurized to 80 °C, no holding. The whey is then evaporated to 50 % solids and flash-cooled to 30 °C.
- Cooling to 25 °C during 5 hours (1 °C/h) in crystallization tanks, during which time sodium hexametaphosphate or sodium polyphosphate to bind Ca++ ions can be added.
- The fat should be mixed with 1-3 % emulsifiers at 60-70 °C before it is mixed with the cold whey concentrate.
- In-line heating by means of a concentrate pre-heat exchanger to 65 °C, followed by a two-stage homogenizing at 80/50 bar g. The holding time of the concentrate at 65 °C should be as short as possible to avoid melting of the lactose crystals.
- Spray drying of fat-enriched whey up to 50 % fat is done in a Multi-Stage Dryer MSD™ with CIP-able bag filter recommended due to its special design, to avoid excessive powder deposits in the plant. For higher fat contents the product becomes difficult to dry and the integrated belt dryer type FILTERMAT™ is chosen.