Identification of the genetic variants of κ-casein in milk by isoelectric focusing electrophoresis

The genetic variants of κ-casein (κ-CN) A and B were analysed in milk from Holstein–Friesian (HF) and Jersey cows by means of isoelectric focusing (IEF) electrophoresis. Milk samples were obtained in triplicate from pure-breed HF and Jersey cows (three of each) to estimate the protein content, casein and purify κ-CN. The protein and casein contents in the milk from both breeds were statistically different ( P <  0.05). The κ-CN A migrates first with an isoelectric point (pI) of 7.2–7.3 and then B with a pI of 7.5–7.7. Differences in the expression proportion of both variants were detected.