The effects of freezing and thawing on mature human milk's contains: A systematic review.

OBJECTIVE: To conduct a systematic review on the effects of freezing and thawing mature human milk at -18 to -20°C for different periods of time on the macronutrients, micronutrients and bioactive content of milk. DESIGN: Before starting the research, the study protocol was recorded in the 'PROSPERO' database. Eleven databases were searched, and eight studies were included in this review. The articles were published between January 2010 and June 2020. MEASUREMENTS AND FINDINGS: Total protein content increased when milk was frozen for 2 days, but this decreased significantly when milk was frozen for >1 week. Total carbohydrate content also increased when milk was frozen for 2 days, and no significant change was observed when milk was frozen for >1 week. Energy content decreased when milk was frozen for >8 weeks. Total fat content decreased as the freezing period of milk increased, and total free fatty acid content increased. Thirty days of freezing led to a non-significant decrease in the vitamin E content of milk. Freezing did not lead to changes in immunological factors in human milk, but decreases in glutathione peroxidase, antioxidant capacity and lactoferrin were observed. KEY CONCLUSIONS: In order to maintain the nutritional and immunological properties of human milk after freezing and thawing, families, especially mothers, should be informed about the effects of storing milk this way. After expressing milk, it is recommended that the date should be written on the freezer bag, so that milk is frozen for a shorter period of time before use.

Nesfatin-1 in Human Milk and Its Association with Infant Anthropometry.

Breastfed infants have different growth patterns to formula-fed infants and are less likely to develop obesity later in life. Nesfatin-1 is an anorexigenic adipokine that was discovered in human milk more than a decade ago, and its role in infant appetite regulation is not clear. Our aim was to describe nesfatin-1 levels in human milk collected 3-4 months postpartum, associations with infant anthropometry, and factors (maternal pre-pregnancy body mass index (mBMI), high weight gain during pregnancy, milk fat, and energy content) possibly influencing nesfatin-1 levels. We hypothesized that nesfatin-1 levels in mother's milk would differ for infants that were large (high weight-for-age Z-score (WAZ)) or small (low WAZ) at the time of milk sample collection. We used enzyme-linked immunosorbent assay to detect the nesfatin-1 concentration in milk samples from mothers to high WAZ (n = 50) and low WAZ (n = 50) infants. We investigated associations between nesfatin-1 levels and infant anthropometry at 3-4 months of age and growth since birth, using linear regression adjusted for mBMI, birth weight, infant sex, and exclusivity of breastfeeding. We found no difference in nesfatin-1 levels between the two groups and no association with infant anthropometry, even after adjusting for potential confounders. However, high nesfatin-1 levels were correlated with low mBMI. Future research should investigate serum nesfatin-1 level in both mothers, infants and associations with growth in breastfed children.

Effect of cold storage on nutrients and immune substances in human milk / 临床儿科杂志

Objective To explore the optimal storage standard of fresh human milk, and to observe the influence of different cold storage condition (time-temperature) on macronutrients (fat, protein, carbohydrates, TS and energy), immune sub-stances (sIgA, lactoferrin, IL-6, 8, 10 and TNF-α) and bacteria indicators of fresh human milk.Methods Fresh milk samples (n=30) were divided and stored at three temperature and nine time points, which are 4℃ (24 h, 48 h, 72 h), -18℃(72 h, 7 d, 14 d, 4 w, 8 w, 12 w), and -80℃ (12 w, 24 w). At each time point, the macronutrients , immune substance, and bacteria colony counts of each milk sample were measured and compared with fresh milk. Results Compared with fresh milk, all indicators with the exception of lactoferrin in stored human milk showed signiifcant difference (P<0.05). Under 4℃ refrigeration condition, fat, IL-6, and TNF-α decreased, bacteria colony counts and Gram-positive colony counts increased over 72 h storage (P<0.05). Under-18℃ freezing condition, fat, protein, TS, energy and IL-6 decreased from 72 h to 12 w storage (P<0.05); carbohydrates and sIgA also decreased from 4 w and 8 w storage, respectively (P<0.05). Under -80℃ freezing condition, fat, protein, TS, energy and IL-6 decreased over 24 W storage (P<0.05).Conclusions The macronutrients, immune substance, and bacteria indicators of human milk were affected obviously by cold storage. Refrigerated at 4℃ should not be longer than 72 h, -80℃ freezing condition should be chosen for more than two months storage.