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Breast Milk - How Should You Store It?
Breast milk is a living substance full of antibodies and enzymes; the way you store and freeze it determines how much of that quality is preserved.
Choosing a bag or container?
There are two options for storing breast milk. The choice depends on the space you have available and how quickly you want to use the milk.
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Rigid containers (bottles/jars): food-safe materials that can withstand freezing: glass or high-quality plastic (free from harmful plasticizers) are ideal.
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Storage bags: designed to freeze flat (space-saving). These can include disposable plastic bags and reusable silicone storage bags.
Tip: Also freeze milk in small portions (in an ice cube tray). This prevents you from having to throw away (leftover) precious milk.
Temperature and time
Breast milk is surprisingly stable, but bacteria get a chance every time the milk warms up.
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Room temperature: Freshly expressed milk stays good for up to 4 hours outside the refrigerator.
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Refrigerator: In the refrigerator (preferably at the back, where it is coldest), it stays optimal for up to 4 days.
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Freezer: In a separate freezer (-18°C), milk stays top quality for at least 6 months. Use the First In - First Out principle so you always use the oldest milk first.
Mixing breast milk
Can you combine milk from different pumping sessions? Yes, but only once they are the same (chilled) temperature .
Thawing and warming without damage
Breast milk is heat-sensitive. It is better to avoid the microwave: 'hot spots' destroy important proteins (antibodies) and greatly reduce quality!
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Slowly: Preferably thaw frozen milk in the refrigerator (takes about 12 hours).
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Quickly: Hold the bottle or bag under running lukewarm water or use a bottle warmer on a low setting (max. 37°C).
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After thawing: Preferably use thawed milk within 24 hours and never refreeze it.
Smell and color tell a story
Frozen breast milk can sometimes have a 'soap-like' smell after thawing. This is caused by the enzyme lipase, which breaks down fats. This is completely safe and most babies drink it without any problems. It is also normal for the milk to separate into layers (fat on top); gently rolling/swishing it (do not shake) will bring the milk back together.
- By An Hermans - Midwife and Lactation Consultant
