Capillary electrophoresis using a hydrophilically coated capillary and a
low pH buffer containing urea has been used to characterize processed cheeses.
Different electrophoretic patterns were obtained depending on the ingredients used
in the blend such as acid casein, rennet casein, sodium and calcium caseinates and
skim milk powder. Isoelectric casein, and sodium and calcium caseinates were shown
to contain intact non-glycosylated κ-casein (κ-CN), while rennet casein contained
only trace amounts of κ-CN and mainly para-κ-CN. Therefore, the addition of casein
or caseinate to processed cheeses has been detected by analysing the intact non-
glycosylated κ-CN. Quantitation of intact non-glycosylated κ-CN in processed
cheeses of known and unknown composition was carried out using a regression curve
from standard mixtures of 150–550 g isoelectric casein/kg total rennet casein. This
capillary electrophoresis method successfully confirmed the addition of isoelectric
casein or caseinate to processed cheeses of known composition. The quantitative
determination range was 0·605–3·688 mg κ-CN/ml. This method cannot be used for
measuring additions of rennet casein or any caseinates that have been exposed to
chymosin.