Antioxidant capacity of fresh and stored breast milk: is −80°C optimal temperature for freeze storage?

Abstract

Objective: To determine total antioxidant capacity and total oxidation status in fresh and freeze stored (at −80°C) breast milk during the stages of lactation. Methods: Samples of colostrum, transitional and mature milk were collected from 44 healthy women at 3, 8 and 30 days after birth. The total milk volume collected (6 ml) was divided in two aliquot parts: 3 ml for the fresh analysis which was done immediately after the extraction and 3 ml for storage under freezing conditions at −80°C for two months. The antioxidant status and oxidative stress of the fresh and stored breast milk were assessed via determination of total antioxidant capacity and total oxidation status. Results: Antioxidant capacity of transitional and mature milk decreased (p = 0.0001, p = 0.028, respectively); however, antioxidant capacity of colostrum did not change by storage at −80°C (p > 0.05). Total antioxidant capacity of fresh and stored breast milk significantly decreased during the stages of lactation (p < 0.0001, p = 0.028, respectively). Total oxidation status showed no significant difference in fresh and stored breast milk during the stages of lactation (p > 0.05). Conclusion: Freeze storage of breast milk at −80°C for two months seems not to be the optimal condition to preserve the antioxidant capacity of breast milk.