N-Nitrosodimethylamine in Nonfat Dry Milk

Abstract

In 1980, using a detection limit of 0.3 ppb, N-nitrosodimethylamine (NDMA) was found in 51 of 71 commercial nonfat dry milk samples. The range for the positive samples was from 0.3 to 6.5 ppb with a mean for all samples of 0.72 ppb. In 1992, the mean MDMA value for 56 samples of instantized nonfat dry milk samples was 1.05 ppb, the range was 0.1 to 5.3 ppb. A comparison of the NDMA content of regular nonfat dry milk powder and instantized powder showed no additional NDMA formation from instantizing. Several researchers have suggested that NDMA in nonfat dry milk forms during the direct-fire drying process while others have contended that the source was fluid milk. Eight tracking experiments in commercial processing plants detected no NDMA until the drying process began. Furthermore, most of the 62 samples of nonfat dry milk prepared by direct-fire drying contained NDMA while eight of nine samples dried by indirect-fire processes did not contain NDMA. Our results indicate that the main source of NDMA in nonfat dry milk is the direct-fire process used in its manufacture.