How is nonfat dry milk made and preserved?

Nonfat dry milk is produced by first concentrating liquid milk through the removal of water, often using heat under a vacuum to prevent cooked flavors. This concentrated liquid is then processed into a powder, most commonly using spray dryers. In this method, the liquid is atomized into a stream of hot air, creating a fine powder that is collected and typically packaged in heavy-duty, plastic-lined paper bags.12

To improve solubility, the powder often undergoes "agglomeration," or instantizing, which involves rewetting the particles to 8–15 percent moisture followed by a second drying cycle.2

Preservation is primarily achieved through dehydration. Most dry milk products are dried to less than 4 percent moisture, a level that effectively prevents bacterial growth and spoilage. Because nonfat dry milk lacks the fat content that leads to oxidation and rancidity, it remains stable for extended periods when kept dry.3