Breast milk is known by many as “liquid gold” and should be taken care of as such. If you are one of those blessed mothers who produce enough to ensure a breast milk bank, or even if you’re receiving breast milk donations to provide the best nutrition for your little one, you will want to make sure it doesn’t go to waste.
Storing breast milk, if done correctly, can provide parents with a sense of security because no matter if the mother is present or even healthy, they can rest assured that the baby will be able to be fed with this precious liquid.
So, how long does warmed milk last? Expressed breast milk can be stored at room temperature, in the refrigerator, or frozen, and the amount of time before it’s consumed varies in each of those cases.
- Expressed breast milk at room temperature can last up to four hours if it’s not in direct contact with sunlight.
- Freshly pumped and refrigerated milk (not defrosted or thawed) last from 4 to 8 days.
- Frozen breast milk can last from 6 to 12 months after freezing.
- Thawed milk in the fridge needs to be used within 24 hours, and if it is left at room temperature, then within 2 hours.
So, before we delve into the specifics of warmed milk, let’s see some storage guidelines.
Breast milk storage guidelines
Here are the steps you can take to ensure good quality and maximum storage time to build your breast milk bank.
To prepare yourself for every pumping session, wash your hands with soap and water, and use alcohol-based hand sanitizer if there’s no water available.
If you’re using a manual or electric pump, make sure that everything is clean, including the tubing (if you see mold inside the tubes, replace them immediately).
In cases where you have to share a pump, no matter if they seem clean, disinfect the pump dials, power switch, and sterilize every part you can before using it.
How to store breast milk
You can safely store breast milk in storage bags, bottles, or food-grade containers explicitly made to keep expressed breast milk. Avoid BPA plastic containers or, if you’re planning to freeze your milk, glass because liquid expands when frozen and may break the bottle.
If you’re using containers, make sure they have a tight-fitting lid, so the breast milk doesn’t get contaminated.
Make sure you label the milk storage bags or containers with the date it was expressed and the number of ounces in each one.
If you are unsure if you will use the expressed milk within four days, then freeze it. This will help protect the quality of the milk. You can freeze it up to a few days after pumping, but you ensure there’s no nutrient degradation by freezing it right away. Remember, you can always thaw it later and feed it to your baby. It’s important to have a plan for your leftover breast milk so that you’re not leaving it at room temperature and so you can also efficiently manage your milk bank.
To avoid unnecessary leftover breast milk, store it in small amounts, like 2-4 ounces or the number of ounces the baby consumes in one feeding. Keep in mind that breast milk, like any liquid, expands as it freezes, so leave some space at the top of the container to make up for that extra space (about an inch would be fine).
When placing the storage container or bag in the fridge or freezer, try placing them at the back or the furthest you can from the door to protect the breast milk from temperature changes that happen every time you open and close the door.
If you express milk at work or somewhere else and have to use an insulated cooler with ice packs, you can keep the baby’s milk there for up to 24 hours and use it or store it in the fridge or freezer as soon as you get home.
Can milk be frozen?
Yes, breast milk can be frozen, and it will last around 6 to 12 months before it needs to be disposed of.
But thawing frozen breast milk should be done consciously to prevent spoiling and ensure the maximum amount of nutrients are still present.
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How to thaw frozen breast milk
When picking a frozen milk container or bag, always follow the rule of first in, first out so that you don’t accidentally waste stored milk over time. So pick the oldest breast milk first and rotate it accordingly to get the best quality before it starts to decrease.
To thaw breast milk, you can place it in the refrigerator overnight, place the breast milk container in warm or lukewarm water, use a bottle warmer or place the closed container under lukewarm running water. It’s not ideal to just leave it at room temperature as it takes the longest to defrost and also increases the risk of bacteria growth.
Don’t use the microwave to thaw or warm breast milk as it can destroy the nutrients and overheat the milk, which can lead to burns on the baby’s mouth.
How long does warmed breast milk last for?
Here’s the time frame to understand when you can use thawed breast milk: reheated or kept at room temperature – within 2 hours, or stored in the refrigerator – within 24 hours. You start counting the time when the breast milk has completely defrosted.
Previously frozen breast milk should not be frozen again. It should be used within the time frame or discarded, and that’s why it’s been suggested to store it in small amounts. But there’s a catch if your breast milk still has ice crystals. It’s not considered completely thawed, and therefore you could safely re-freeze it.
According to the CDC, after the milk is warmed, bacterial growth begins more quickly with previously frozen milk.
Once you have thawed breast milk, you can give it to your baby, either warm or cold milk. It’s a matter of preference and what your baby likes. There’s no harm in giving cold milk to a baby. If you decide to warm the breast milk, it’s recommended you warm milk with a bottle warmer, place it in a bowl of warm water for a few minutes or hold it under warm running tap water.
Remember, microwaves are not recommended for this purpose. A stove is also not the best heating method because if the water boils, you risk overheating the breast milk, destroying the nutrients, and making it too hot for consumption.
Once the milk is warm, swirl it to mix any separated content (this is very common and normal) and check the temperature by dropping a bit on the inside of your arm before giving it to your baby. The correct temperature should feel lukewarm or room temperature, not hot or cold.
Leftover milk that’s been reheated, contrary to recently thawed breast milk, should not be kept at room temperature or stored in the fridge. Unfortunately, you’ll need to throw away the rest in these cases.
How do I know if the stored milk is safe to use?
Breast milk, like any other type of milk, can spoil. If you want to make sure the breast milk you have stored is safe for consumption, the first thing you need to do is smell it and taste it. If it smells rotten and tastes sour, it needs to be thrown away.
Spoiled milk can look curdled, so if you notice that the breast milk in the container looks separated and doesn’t mix back up easily when you swirl it or has chunks floating, then it’s time to throw it out.
Tips for handling breast milk storage
Here are some safety guidelines to ensure your milk retains as many nutritional properties as possible when you need to use it.
- If you have a container or storage bag that still has some space available, you can add more breast milk, but it needs to be thoroughly cooled first. You need to place the fresh breast milk in the fridge to cool, and once it has the desired temperature, you can add it to the one you had already stored in the refrigerator or freezer. If you add warm or body temperature breast milk to frozen milk, it will partially thaw it and degrade slightly.
- When storing in the freezer or refrigerator, try to place the container in the back because that’s where it’s colder. With self-defrosting freezers, avoid placing the breast milk containers where it touches the walls because the temperature may fluctuate and degrade the milk.
- There are plenty of options available for storage containers that have been specially designed for breast milk. They are made with materials that can be sanitized (or come previously sterilized, like storage bags), and that won’t negatively affect the quality of the breast milk. Choose those and keep in mind that breast milk expands when frozen, so don’t overfill them.
- Here’s a temperature reference for storing breast milk correctly:
- Room temperature: 77°F / 25°C to be used within 4-8 hours.
- Insulated cooler bag with ice packs: 59°F / 15°C to be used within 24 hours or stored in the refrigerator or freezer after that time frame.
- Refrigerator: around 39.2°F / 4°C to be used within 4 days. If you won’t be using it in that time frame, then freeze it.
- Freezer: 24.8°F / -4°C and can be stored for 6-12 months.
- When warming breast milk, keep the container or bottle closed to prevent contamination and check the temperature of the milk on your arm before feeding it to your baby, so it’s not overheated and doesn’t burn your baby’s mouth.
- If you notice that your previously frozen breast milk has a metallic or soapy smell, it’s a sign of high lipase. Lipase is the enzyme that helps the baby digest breast milk and absorb the nutrients. In high concentration, it may cause your breast milk taste to change, and you may notice that your baby refuses it. To avoid this, you can scald the milk before freezing it. This is the process: heat milk on a pan or in a bottle warmer bottle until bubbles start and before it starts boiling (remember boiling it may destroy the nutrients). When bubbles start to form around the edges, remove it from the heat and quickly cool it in an ice bath to reduce the temperature before storing it. You can then refrigerate or freeze it.
- Any leftover breast milk that is left over, needs to be discarded.
- Milk left at room temperature always lasts the shortest amount of time, so it’s best to either freeze or put excess milk directly into containers and into the fridge, that will help the milk retain the most nutrients and stay safe for your little one.