Properties and stability of butter oil obtained from milk and yoghurt

The physical and chemical characteristics and thermal stability of butter o il produced from cow's milk by two different methods were studied. Butter o il samples from cow's milk were made (i) directly from milk and (ii) from y oghurt. Samples were autoxidized at 60, 70 and 80 degrees C in the dark and the reaction monitored by peroxide, thiobarbituric acid and free fatty aci d values. Peroxide and thiobarbituric acid values increased as the temperat ure increased. The increase of the acid value was not significant. The ther mal stability was highest in butter oil produced from yoghurt. Oxidative ch anges compared to hydrolytic changes are of greater significance in the the rmal stability of butter oil samples. Arrehenius parameters and activation energies were calculated for the peroxide value data. The percent loss of l inolenic acid was about 3 times faster than that of linoleic acid.