Determination of a nitrogen conversion factor for protein content in Cheddar cheese

As the protein composition of Cheddar cheese varies substantially from that of milk, it is important to investigate whether the standard dairy nitrogen conversion factor (NCF), 6.38, accurately reflects the protein content of Cheddar cheese. Forty-eight Cheddar cheeses of a wide range of composition were manufactured. Amino acid compositions of measured casein subtypes, peptides and amino acids in the cheeses were used to calculate a nitrogen conversion factor for each cheese. Average NCF values were calculated as 6.394±0.004, for the full dataset, which is slightly higher than the standard dairy nitrogen conversion factor of 6.38.