Effect of storage on breast milk antioxidant activity

Abstract

Background: Human milk, which contains compounds beneficial to infants, is often expressed and stored before use. Changes in its antioxidant activity with storage have not been studied. Objectives: To measure antioxidant activity of fresh, refrigerated (4˚C), and frozen human milk (220˚C), stored for two to seven days; to compare the antioxidant activity of milk from mothers delivering prematurely and at term; to compare the antioxidant activity of infant formulas and human milk. Methods: Sixteen breast milk samples (term and preterm) were collected from mothers within 24 hours of delivery and divided into aliquots. Fresh samples were immediately tested for antioxidant activity, and the rest of the aliquots were stored at 220˚C or 4˚C to be analysed at 48 hours and seven days respectively. The assay used measures the ability of milk samples to inhibit the oxidation of 2,29-azino-di-3-(ethylbenzthiazolinesulphonate) to its radical cation compared with Trolox. Results: Antioxidant activity at both refrigeration and freezing temperatures was significantly decreased. Freezing resulted in a greater decrease than refrigeration, and storage for seven days resulted in lower antioxidant activity than storage for 48 hours. There was no difference in milk from mothers who delivered prematurely or at term. Significantly lower antioxidant activity was noted in formula milk than in fresh human milk. Conclusions: To preserve the antioxidant activity of human milk, storage time should be limited to 48 hours. Refrigeration is better than freezing and thawing.

Stability of Antioxidant Capacity of Human Milk after Freezing and Pasteurization

“…These advantages are even more important in preterm newborns, because they have an immature antioxidant defense system, since it develops during the course of gestation [5]. In addition, they are often exposed to oxidative stress caused by infections, mechanical ventilation, intravenous nutrition and blood transfusions [6]. Several studies have shown that the antioxidant capacity of HM is superior to infant formulas and bovine milk [2,6,7].…”

“…However, according to Sari et al [4], the freezing samples of colostrum, transition and mature milk at -80 °C for two months did not preserve the antioxidant capacity. According to Hanna et al [6], the antioxidant capacity of HM also decreased with the storage time and refrigeration was better than freezing to preserve it, because the freezing for 48 hours caused greater losses than the refrigeration for seven days.…”

“…In addition, they are often exposed to oxidative stress caused by infections, mechanical ventilation, intravenous nutrition and blood transfusions [6]. Several studies have shown that the antioxidant capacity of HM is superior to infant formulas and bovine milk [2,6,7]. The production of free radicals caused by oxidative stress can lead to diseases both in the infancy and in the adult phase [5].…”

“…They also verified that these losses may be to a lesser or greater extent, depending on the type of process adopted. Regarding storage, the studies to date are still not conclusive [4,5,6]. According to Akdag et al [5], the total antioxidant capacity of preterm HM was preserved at -80 °C for 3 months.…”

“…Given the known importance of bioactive compounds and antioxidant capacity for the development and health of children [3,4,5,6] and the limited literature that evaluate the real conditions of the processing stages of HM by the Network of Human Milk Banks in Brazil, it is important to conduct studies to evaluate the stability of the antioxidant capacity of HM after the procedures adopted. Therefore, this study evaluated the interference of the freezing time and the pasteurization of HM on the content of total phenolic compounds and antioxidant capacity in vitro.…”