150. The effect of certain metallic contaminants on the Cheddar cheese making process

Abstract

Traces of certain metallic contaminants (copper, iron, lead, zinc, aluminium and manganese), when added at the rate of 3 and 7 p.p.m. to milk used for the manufacture of Cheddar cheese, cause certain flavour (and colour) defects in the matured cheeses, of which, however, no indication is given when the cheese is plugged and graded at about 14 days after manufacture.The distribution of copper, iron, manganese and lead between curd and whey during the cheese-making process is recorded and the action of traces of various metals on the acidity development in a typical "starter" culture has been followed.The discolorations noted for copper- and iron-contaminated cheeses are considered to be due not to the formation of their sulphides (although this is the case for lead discoloration), but to the atmospheric oxidation of a colourless metal: protein complex.