Breast milk is a well-balanced ideal nutritional source with high bioavailability for infants. As being a fresh, biological and dynamic product, changes in the breast milk during these storage periods have been the subject of ongoing research. This study aims to evaluate total antioxidant capacity (TAC), total oxidant status (TOS), and paraoxonase-1 (PON-1) levels of fresh and freezestored breast milk. Ten cc of breast milk was obtained from the mothers as the days between 10 and 15 in the morning within a 1-hour period. TAC, TOS, and PON-1 levels were evaluated in the fresh breast milk. Collected breast milk samples were divided into two groups for storage at -20°C or -80°C. Stored samples were tested for TAC, TOS, and PON-1 levels after 72 hours. The highest TAC level was detected in fresh breast milk (p < 0.05). The TOS levels of fresh breast milk showed a statistically significant reduction in rate after storage. The TOS levels at -20°C and -80°C were significantly lower at -80°C (p < 0.05). Our study results show that oxidant and antioxidant activities are at the maximum level in the fresh breast milk. In terms of antioxidant status the effect of freezing temperatures hasn`t been determined. We conclude that it is more convenient to store the breast milk at -80°C than to store at -20°C in terms of preserving the storage TOS level.

Keywords: antioxidant status, oxidant status, paraoxonase-1, stored breast milk