Approfondimenti scientifici
Storage of Breast Milk
Breast milk is the nutritional and immunological gold standard for both term and preterm infants. Expressing and storing breast milk for later use is an essential practice in many clinical and home settings, ensuring continuity of the nutritional and functional benefits of human milk when direct breastfeeding is not possible.
Clinical and Physiological Rationale for Breast Milk Storage
Breast milk storage is necessary in several situations:
- Temporary maternal absence (e.g., return to work, separation, travel, or logistical reasons);
- Delayed breastfeeding in preterm, hypotonic, or medically compromised infants who are unable to suck effectively;
- Support of lactogenesis when direct breastfeeding is temporarily not possible while maintaining stimulation of milk production (e.g., mothers with breast engorgement, mastitis, or when the newborn is hospitalized);
- Shared infant care by encouraging the participation of the partner or other caregivers;
- Donation to a Human Milk Bank (HMB) for preterm or critically ill newborns.
Properly stored human milk retains a high biological value and remains preferable to infant formula, even when administered indirectly.
Bioactive Components of Breast Milk: Sensitivity to Storage
Human milk contains numerous bioactive components that are highly sensitive to changes in temperature, light, storage duration, and handling procedures. Improper storage may reduce their biological activity or cause irreversible degradation. The principal thermo- and photosensitive components include:
| Component | Function | Damage Caused by Improper Storage |
|---|---|---|
| Immunoglobulins (IgA, IgG, IgM) |
Mucosal protection, pathogen neutralization | Loss of activity at temperatures >4°C or after refreezing; IgA particularly affected |
| Lactoferrin | Iron chelation, antimicrobial and antiviral activity | Sensitive to heat and oxidation; uncontrolled pasteurization reduces activity |
| Lysozyme | Antibacterial enzymatic activity (against Gram-positive bacteria) | Denaturation during freeze–thaw cycles; activity decreases after a few days of refrigeration |
| Living cells (maternal leukocytes) |
Immune response and regulation of neonatal immunity | Complete loss of viability after freezing; maximum effectiveness only in fresh milk |
| Digestive enzymes (lipase, amylase) |
Digestion of fats and carbohydrates; gastrointestinal protection | Progressive inactivation after 24–48 hours at 4°C; freezing reduces activity |
| Human Milk Oligosaccharides (HMOs) |
Microbiota modulation, prebiotic activity, and prevention of pathogen adhesion | Stable at low temperatures, but light and air reduce bioactive effectiveness |
| Vitamins (A, E, C, B-complex) |
Metabolic support, antioxidant activity, neurological development | Vitamin C is particularly sensitive to oxidation; rapid degradation with exposure to air, light, and room temperature |
Practical Recommendations for Proper Expression and Storage
To preserve the nutritional and immunological properties of breast milk, appropriate hygienic and handling practices are essential.
During milk expression:
- Choose a clean and quiet environment;
- Wash hands and forearms thoroughly with soap and water;
- Clean the breast using only water, without detergents;
- Use clean glass or rigid plastic containers, or sterile single-use storage bags;
- When expressing milk manually, position the container beneath the areola;
- Each expression session should be stored in a separate container. At the end of the day, refrigerated milk expressed at different times may be combined into a single container.
For refrigeration:
- Store milk at the back of the refrigerator in an upright position, preferably inside a food-safe storage bag;
- Label each container with the date of expression;
- Never reheat milk that has already been warmed, and do not return it to the refrigerator after use.
For freezing:
- Leave approximately 2 cm (about 1 inch) of empty space in the container to allow for expansion during freezing;
- Thaw slowly in the refrigerator, under running water below 37°C (98.6°F), or in a warm water bath;
- Thawed milk should never be refrozen;
- A slight change in odor or color after thawing is normal and does not indicate a loss of quality.
