Determination of endogenous concentrations of nitrites and nitrates in different types of cheese in the United States: method development and validation using ion chromatography.

Nitrites and nitrates can be present in dairy products from both endogenous and exogenous sources. In the European Union (EU), 150 mg kg of nitrates are allowed to be added to the cheese milk during the manufacturing process. The CODEX General Standard for Food Additives has a maximum permitted level of 50 mg kg residue in cheese, while in the United States (U.S.) nitrates are unapproved for use as food additives in cheese. In order to be able to investigate imported cheeses for nitrates intentionally added as preservatives and the endogenous concentrations of nitrates and nitrites present in cheeses in the U.S. marketplace, a method was developed and validated using ion chromatography with conductivity detection. A market sampling of cheese samples purchased in the Washington DC metro area was performed. In 64 samples of cheese, concentrations ranged from below the method detection limit (MDL) to 26 mg kg for nitrates and no concentrations of nitrites were found in any of the cheese samples above the MDL of 0.1 mg kg. A majority of the samples (93%) had concentrations below 10 mg kg, which indicate the presence of endogenous nitrates. The samples with concentrations above 10 mg kg were mainly processed cheese spread, which can contain additional ingredients often of plant-based origin. These ingredients are likely the cause of the elevated nitrate concentrations. The analysis of 12 additional cheese samples that are liable to the intentional addition of nitrates, 9 of which were imported, indicated that in this limited study, concentrations of nitrate in the U.S.-produced cheeses did not differ from those in imported samples.