Breast Milk 101

Breast Milk 101

You've made it through the hard part! Woo hoo! Now... how do I do this whole Breast Milk thing? Check out our Breast Milk 101 guide which features some frequently asked questions by new and expecting mothers.


Why do women express Breast Milk?

There are various reasons women express breast milk, but some include:

Returning to work: Returning to work in either a full or part time basis does not mean the end of your breastfeeding journey. Many women continue to express breast milk once they return to work, store it in a fridge or small cooler bag and take it home at the end of the day.

Premature or unwell baby: Some babies are too small (premature), unwell or unable to feed directly from the breast. Breast milk is expressed and fed to the baby via a bottle or naso gastric tube directly into the stomach allowing your baby to still receive your liquid gold.

Share the love: Some mothers express breast milk so they can have another family member feed the baby in their absence. This could be so their partner can feed the baby during the night or if mum needs to spend time away from baby.

Milk supply: If establishing and maintaining milk supply has been a problem, some mothers decide to express breast milk to ensure they have enough milk to keep their baby fed.

How do I store Breast Milk?

Breast milk can be stored in a clean glass or hard plastic container. Ameda Breast Milk Storage Bags are also an option. Avoid thin, flimsy storage bags as these can easily tear. Always write a date on the outside of the breast milk container so you know how long it has been frozen.

If you follow the recommended breast milk storage times, you can keep your milk at room temperature, refrigerate it and then freeze it.

Remember to only store as much milk in a container as your baby might consume to avoid waste.

Why does my Breast Milk change colour when frozen?

When you pump and store breast milk, it can change in appearance. In the refrigerator, breast milk may separate into layers. There may be a thick, white or yellow creamy layer on top, and a thinner clear or blue-tinted layer on the bottom. Don't worry, It's normal. This doesn't mean there is anything wrong with the milk, It's just the way the milk settles with the fat rising to the top. When you're ready to use your frozen milk, gently mix the layers by swirling the bottle around. Breast Milk can also change colour in the freezer. Frozen breast milk may have a yellow tinge to it. (3)

Can I mix fresh and frozen Breast Milk?

You can add freshly expressed breast milk to refrigerated or frozen milk you have already expressed. Thoroughly cool the freshly expressed breast milk in the refrigerator before adding it to previously chilled or frozen milk. Don't add warm breast milk to frozen breast milk as it can cause the frozen milk to partially thaw. (4)

Do I need to date Breast Milk in the freezer?

Yes! You need to date breast milk stored in the freezer. By dating the breast milk container, you will know when the ‘use by’ date is approaching. 

How do I date Breast Milk?

Clearly label the outside of the breast milk storage container. Use a non-toxic marking pen or adhere a sticky label to the container or breast milk storage bag. Add your baby’s name if they are in daycare or hospital.

How long can I store frozen Breast Milk?

Breast Milk Storage Guide










**chest or upright manual defrost deep freezer that is opened infrequently and maintains ideal temperature.
Reproduced with permission from National Health and Medical Research Council 2012, ionfant feeding guidelines, NHMRC, Canberra p59

How can I tell if Breast Milk is 'off'?

Odour: Similarly to cow’s milk, breast milk will smell sour if it has gone off.
Do not confuse a soapy or metallic smell as these smells can be normal for some breast milk. A soapy or metallic smell can be caused by a higher levels of enzymes lipase that some mothers will produce. There is nothing harmful about a soapy smell. (3) 

Left in the fridge for longer than 3 days: According to the NHMRC Infant Feeding Guidelines, breast milk can stay refrigerated for up to 72 hours. It is best placed in the centre of the fridge where temperature is coolest and most consistent. Avoid the fridge door.

Wasn’t sealed properly: Like anything, if your breast milk wasn't sealed properly or the bag or container had a tear in it, the chances of your milk spoiling increases. General industry recommendation is that breast milk should stored in clean glass, firm plastic containers or specifically designed Milk storage bags. These containers are less likely to tear or allow contaminants into the milk

It tastes sour: Taste is the easiest way to determine if breast milk is off. Like cow’s milk, if breast milk is off it will have a distinctly unpleasant and sour taste. If in doubt, throw it out

Doesn’t mix when swirled: Although breast milk often separates into fatty and non-fatty layers when stored, if the milk is still fresh it should re-congeal with a gentle swirl. If your breast milk doesn't mix when swirled, or if there are chunks in the milk that won't mix, it's likely to be spoiled.

Where in the fridge should I store Breast Milk?

Breast milk should be stored in the centre of the fridge where it is coolest and consistently the same temperature. Avoid the door as this will fluctuate in temperature as the fridge door is opened and closed.

Should I Breastfeed if I'm sick?

With rare exceptions, it is better for your baby to be fed breast milk (expressed or directly from the breast) while you are unwell. Once you have symptoms, your baby has already been exposed because you are contagious just before your symptoms appear. One of the first things your body does when you become sick is to produce specific antibodies that fight that illness that go right into your milk.

If your baby continues to consume breast milk, the antibodies in your milk will either prevent the baby from catching the illness or if the baby does get sick it will present with milder symptoms.

Can I add Breast Milk to my baby's food?

Yes! Breast Milk is a great addition to your baby's food.

Why does my Breast Milk smell 'soapy'?

Some women have milk high in an enzyme called lipase. This is normal for them but can cause their milk to smell ‘soapy’ after freezing. Some babies are not concerned by the taste, however some will refuse to drink high lipase, thawed milk. To prevent milk from developing this smell, scald it briefly before freezing. You can scald the breast milk by heating it in a pot on the stove top until bubbles form around the edges. Cool the milk before freezing.

How do I defrost Breast Milk?

• Thaw frozen breast milk by moving it from the freezer to the fridge for slow thawing over 24 hours.
• You can also run cold water over the container and gradually increase the temperature of the water. Do not overheat the milk as it will destroy some of the nutrients and may burn the baby’s mouth.
Never use the microwave. It is a potentially dangerous practice as it can cause ‘hot spots’ in the milk that may burn your baby’s mouth.

How do I warm Breast Milk?

If a newborn is fed cold milk, it can bring down their body temperature. Milk given to a newborn should always be at body temperature. If you are either thawing or warming milk, keep the heat on low. Heat destroys the nutrients in breast milk.
To warm breast milk, run warm water over the sides of the container. Keep the warm water away from the lid so it doesn’t mix with the milk.

An easy way to warm breast milk is to place the container or bottle in a bowl with sides lower then the bottle lid. Run warm water into the bowl. The warm water against the bottle warms the milk. The milk is ready when it reaches body temperature (32-37°c).

Can I put Breast Milk in the microwave?

Never use the microwave. It is a potentially dangerous practice as it can cause ‘hot spots’ in the milk that may burn your baby’s mouth.

Why does my Breast Milk have different layers?

Breast milk is made up of fore milk and hind milk. The essential difference between the 2 is that the hind milk has a greater fat content than the more watery foremilk. The 2 can appear in ‘layers’ within a container.

Foremilk is produced at the beginning of the feed and hind milk at the end of the feed. Fir this reason, it’s important to completely drain one breast before offering the second. (5)

Why does my Breast Milk look different every day?

Breast milk will change in consistency and composition to reflect what the baby needs. In hotter climates, breast milk will have greater hydration content than on cooler days.

Colostrum: Colostrum is the first breast milk that your body makes. You only make a small amount of colostrum, but it's concentrated and highly nutritious. While colostrum is sometimes clear, thin, and watery, it's more often yellow or orange and thick. The high levels of beta-carotene in colostrum give it its dark yellow or orange color.

Transitional Milk: After the first few days of colostrum, the production of breast milk increases and your body begins to make transitional milk. During this two week transition period, the colour of breast milk typically changes from yellow to white as your milk comes in.

Mature Milk: After about two weeks, your body reaches the mature milk stage. Mature breast milk changes in appearance based on how much fat it contains.

    • Foremilk: In general, when the mature milk begins to flow out of your breast at the beginning of a feeding or pumping session, it is thinner and lower in fat. This milk is called the foremilk. Since foremilk is thin, it tends to look clear or bluish.
    • Hindmilk: As you continue to pump or breastfeed, the fat content in your milk goes up. As the fat increases, breast milk turns into creamier milk called hindmilk. Hindmilk has a thicker white or yellow appearance.


I have more Breast Milk questions, who do I ask?

If you have any breastfeeding questions or problems, you need to speak with a healthcare provider and or someone with the credential IBCLC – an International Board Certified Lactation Consultant. To find an IBCLC call your local hospital, GP or community health centre. Alternatively search on the internet or go to the following websites – or

The Australian Breastfeeding Association (ABA) is a great resource and can be contacted on 1800 mum 2 mum (1800 686 268). The ABA also offers smaller community support groups and will be able to put you in contact with your local co-ordinator.


Enjoyed this blog? Leave a comment and let us know what you would like to hear about next!

This is general information and does not replace the advice of your healthcare provider. If you have a problem you cannot solve quickly, seek help right away. Every baby is different. If in doubt, contact your physician or healthcare provider.


1. Murray, D. (2012, April 29). Breast Milk Color, How It Changes, and What's Normal. Retrieved from

2. Mayo Clinic. (2018, April 6). Breast milk storage: Do's and don'ts. Retrieved from

3. Youngs, O. (2016, October 21). 5 Signs Your Breast Milk Has Gone Bad. Retrieved from

4. Better Health Channel. (2011). Breastfeeding - expressing breastmilk. Retrieved from

5. Bonyata, K. (2018, January 1). Foremilk and hindmilk - what does this mean? • Retrieved from

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