During the past two years, discoloration, owing to its prevalence in Cheddar cheese, has been the subject of much investigation by the New Zealand Dairy Division, and in the present paper are incorporated details of the observations made in this laboratory and in cheese stores in New Zealand and England, together with short reports on the same subject from English laboratories.

To avoid confusion it must be emphasised that the defects dealt with are “bleached,” “pink” and “muddy” discolorations only. The observations do not apply to “black spot” (due to lead or other metallic contamination), nor to “red spots” (due to faulty annatto), nor to “acid cut” bleaching which seems to follow the outline of the original pieces of curd. Muddy or dark discoloration occurs in white and in coloured cheese, but the bleaching and pink discoloration dealt with here are confined to coloured cheese.