Physical and chemical properties of milk fat and its fractions

Supercritical carbon dioxide was used to fractionate milk fat produced through seasons of a year. Six fractions (F1-F6) were produced using pressure values of 10-36 MPa. Milk fat and their fractions were analyzed for fatty acids, triglycerides, iodine number, color, thermal behavior, rheological properties and crystal forms. Short chain, medium and total saturated fatty acids were decreased from fraction obtained in the order of F1 to F6, while long chain and total unsaturated fatty acids were increased. Fractions obtained in the raffinate column exhibited higher melting behavior that obtained at the low CO2 pressures. The higher iodine value of raffinate fraction indicated that fraction was richer in long chain unsaturated fatty acids. Yellowness Index value increased in raffinate fraction due to concentration of carotenoids. When activation energy of the fractions was compared, raffinate fraction was more susceptible to thermal oxidation than those of the other fractions due to high content of polyunsatured fatty acids containing triglycerides.