Milk Powder Manufacturing Procedures
- Milk manufacturing plants process whole milk to make a variety of powders, including whole milk, skimmed milk, buttermilk, as well as whey protein powder. These different powders are then sold to the public for household cooking, or sent to food manufacturers as use as additives in dairy products and baked goods. A high quality powdered product will provide the original qualities of milk when it is reconstituted with water. The basic steps are stabilization, evaporation and finally, drying.
- There are special challenges in converting whole milk from liquid to a powder. Since whole milk contains fat, it must first be stabilized to prevent oxidation and spoilage. When raw milk arrives at a processing plant, it is first divided into cream and skim milk. The liquids are then pasteurized between 72 and 120 degrees F Celsius for 4 to 16 seconds and flash cooled to below 50 degrees Celsius. The higher the temperature milk processing plant uses, the fewer seconds it requires. Pasteurization stabilizes the fats and can now receive further processing. For whole milk powder, some of the cream is then returned to the skimmed milk to raise the fat content back to normal. In the finished product, fat content ranges between 26 to 30 percent. The next step for both whole and skim milk powder is evaporation. The pasteurized milk is boiled in a closed system that sends it through a series of tubes until it has lost enough water to bring the solids up to 45 to 52 percent of the total weight. Before the evaporation process began, whole milk contained 13 percent solid materials and skim milk around 9 percent solids.
- There is still another step, as at this point the milk powder is still almost half water. Drying helps eliminate the extra water, and large scale milk processing plants use spray dryers. Spray dryers force very hot air, up to 200 degrees Celsius, up tubes that contain the milky mixture. The high heat evaporates the water and the powder is sprayed out through an atomizer or nozzles. This step lowers the moisture content from just under half to about 6 percent, but more moisture needs to be removed. To reach the ideal moisture level of 2 to 4 percent, the powder is laid out on trays, or beds, and more hot air is blown through it. Some plants have another step for whole milk powder, called lecithination. This adds soy lecithin mixed with oil to the whole milk, which will produce a final product that dissolves well in water. Once the milk powder has been cooled down, it is packed into plastic bags or tins with lids that close tightly.