Expressing and storing human milk provides flexibility and ensures a consistent supply for the baby, particularly for working parents or those managing an oversupply. Freezing is a widely adopted and effective preservation method that significantly extends the lifespan of this collected milk. Clear, evidence-based guidelines are necessary to protect the milk’s unique nutritional and immunological properties while maintaining safety for the infant.
Storage Rules for Thawed Milk
Once frozen breast milk is removed from the freezer, it enters a limited consumption window based on the temperature at which it is thawed and stored. Guidelines for previously frozen milk are significantly shorter than those for fresh milk to ensure safety. The clock begins ticking the moment the last ice crystal disappears and the milk is completely liquid.
If the milk is thawed slowly in the refrigerator, it should be used within 24 hours of being fully liquefied. This method is preferred as it keeps the milk at a consistently low temperature, minimizing bacterial growth. Thawed milk should not be stored in the refrigerator door, as this area is subject to the most temperature fluctuation.
If the milk is thawed quickly under warm running water or in a bowl of warm water, it should be used within two hours of reaching room temperature. Warming milk encourages the multiplication of naturally present bacteria. Once an infant begins feeding from a bottle of thawed milk, any remaining milk must be used within two hours or discarded due to bacteria introduced from the baby’s mouth.
Refreezing Thawed Breast Milk
Health authorities and medical organizations advise against refreezing breast milk that has been completely thawed. This recommendation is based on concerns regarding both the safety and the quality of the milk after a second freeze-thaw cycle. The primary concern is the potential for bacterial proliferation, which increases the risk of contamination for the infant.
The initial thawing process exposes the milk to temperatures that allow naturally present bacteria to begin multiplying. While refrigeration slows this growth, a second freezing and subsequent thawing provides another opportunity for bacteria to multiply exponentially. Repeatedly moving the milk through the temperature danger zone compromises the milk’s safety profile.
Beyond safety, the quality of the milk sustains damage during repeated freezing and thawing. The structure of the milk’s components is affected, leading to the breakdown of fat globules and proteins. This degradation results in a measurable loss of beneficial immune properties, such as immunoglobulins and white blood cells.
The process also affects the milk’s taste and appearance. A soapy or metallic smell may occur due to the activity of the enzyme lipase, which breaks down milk fats. Refreezing and re-thawing can accelerate this enzymatic process, potentially making the flavor unappealing to the baby, which may lead to bottle refusal. The only exception to the refreezing rule is if the milk still contains ice crystals, indicating it was only partially thawed and maintained a temperature below freezing.
Practical Ways to Reduce Waste
To prevent the dilemma of having excess thawed milk that cannot be refrozen, parents can implement proactive storage strategies. Freezing milk in smaller batches is the most effective preventative measure. Storing milk in one to four-ounce portions, which is typically the amount consumed in a single feeding, ensures that only the necessary volume is thawed at one time.
If milk has been thawed but is past the safe consumption window, it can still be utilized for non-feeding purposes rather than being poured out. The milk retains many beneficial properties, making it excellent for external use. Adding a few ounces of unused milk to a baby’s bath can help soothe skin conditions like eczema, diaper rash, and cradle cap due to its moisturizing and anti-inflammatory components.
The milk can also be used to create homemade topical remedies. Some parents use thawed milk to make lotions or soaps, taking advantage of its natural fats and immune factors to treat minor skin irritations. Even if the milk has passed its expiration date for consumption, it can still be repurposed for these creative, non-ingested uses, ensuring that every drop of the collected milk is used efficiently.