Redox potential of cow milk at three different months of the year

The present study examined the effects of seasons on the redox potential be havior of milk, and the objectives were to evaluate the dependence of the m ilk's oxidative stability on season. The oxidative stability was studied in the reaction with 1,4-benzoquinone (pbc). Metabolic transformation involvi ng electron-transfer reactions and chemical reactivity of pbc play a centra l role in the assessment of redox equilibrium. Milk samples from 278 cows randomly assigned to 3 groups were taken in Janu ary, March, and September, respectively. The following parameters were dete rmined: the start level of the redox potential and the level after adding 1 0, 20 and 30 mu g pbc to the samples. The January milk samples showed the h ighest potential (217.8 mV) and the most intensive decrease in redox values (69.3 mV) after the addition of pbc, which indicated poor oxidative stabil ity. The curve of the March milk samples showed a lower potential (175.6 mV ) and a smaller decrease (53.5 mV) compared with the winter samples. In the September milk, was found the lowest potential (143.4 mV) and the slightes t slope (27 mV); which means the best oxidative stability.