The effect of freeze-drying on the nutrient, polyphenol and oxidant levels of breast milk

Abstract

Human milk banks need to extend the suitability of milk for breastfeeding, and for this technological advances are required. Our aim was to establish the capacity of freeze-drying to conserve milk properties without further oxidative deterioration. Methods: One hundred sixteen healthy women participated from the city of Cordoba (Argentina). Proteins, glucose, triglycerides, polyphenols, and markers (nitrites, superoxide anion, hydroperoxides, lipoperoxides, and γ-glutamyl transpeptidase) were measured in their fresh milk. Samples were then separated for three treatments as follows: freezing and conservation for 6 months at-80°C (F: positive control); freeze-drying for 24 hours at ≤-70°C and ≤1.33 Pa and conservation for 6 months at 4°C (FD: treatment of interest); and freeze-drying for 24 hours at ≤-70°C and ≤1.33 Pa and conservation for 6 months at-80°C (FD+F). Next, analyses were repeated and compared by ANOVA and Tukey tests. Results: Fresh milk showed these values per L as follows: proteins: 12.62 ± 2.51 g, glucose: 4.44 ± 0.25 g, triglycerides: 34.26 ± 0.59 g, polyphenols: 53.27 ± 8.67 mg, nitrites: 62.40 ± 19.09 mg, superoxide: 3,721.02 ± 198.80 OD, hydroperoxides: 7,343.76 ± 294.53 OD, lipoperoxides: 7,349.72 ± 398.72 OD, and γ-glutamyl transpeptidase: 4.66 ± 0.55 IU. Glucose was decreased after F treatment (p < 0.05), all variables were conserved by FD and were not improved by the FD + F combination. Conclusions: Freeze-drying achieved suitable conservation and may improve bank functioning, by protecting nutritional properties, polyphenol-related functionality, and oxidative integrity of human milk through a 1-day treatment with easy maintenance.