Our Ultimate Guide to Storing Breast Milk For Aussie Mums & Dads

 

Whether you're new to parenting or have been at it for a while, at some point, you’ve probably wondered, “So, how long can this breast milk sit out?”. Well, knowing how to safely store breast milk is key to giving your baby the nutrition they need. 

Breast milk is full of all the nutrients vital for your baby's growth and immune health. And if you’ve decided to pump breast milk for your little one, proper storage is key to making the most of this ‘liquid gold’.

 

Why Proper Breast Milk Storage Matters

First and foremost, your breast milk is tailored nutrition for your baby, packed with all the antibodies, vitamins, and good fats your baby needs to grow strong. 

If you can breastfeed and have enough for storing, then understanding how to store your milk properly ensures your baby gets the best quality milk. 

Breast milk can be stored at room temperature right when expressed, in the fridge, freezer, or even in the newest, most innovative way, freeze-drying into a powder (but more on that in a bit). With Australia’s warm climate, it’s even more important to follow safe storage practices.

The NHMRC (Australia’s National Health and Medical Research Council) published their Infant Feeding Guidelines in 2021 which provides evidence-based advice for feeding infants and this includes storage of expressed breast milk.

 

Benefits of following the NHMRC’s guidelines for safe breast milk storage:

• Preserves essential nutrients and antibodies that boost your baby's immune system.
  
• Allows for easy tracking of milk consumption and storage dates, ensuring the freshness of your breast milk.
  
• Supports breastfeeding continuity, even during times of separation from your baby, a busy schedule or when mums are not around.
  
• Provides peace of mind knowing your baby is getting the best nutrition possible.
  

 

Getting Started: Before You Store Your Expressed Breast Milk

Proper storage of expressed breast milk is so important for babies to maintain its nutritional value and safety. Here are the basics:

Hygiene First

• Always wash your hands with soap and warm water before expressing or handling breast milk. 
• Clean and sterilise all equipment, including pumps and storage containers. If you use a pump kit, inspect the pump kit and especially the tubing to ensure it is clean. Replace any mouldy tubing immediately.
• Clean your countertops or the area you work with the expressed breast milk with disinfectant.

Storage Containers

• Choose BPA-free plastic bags, glass jars, or hard plastic bottles specifically designed for breast milk.
• Don’t use regular plastic bags or containers that could leach chemicals.
• Ensure your storage option is cleaned and sanitised before you pour your liquid gold into the container.

Labelling

• Label each storage container or bag with the date you expressed the milk.
• Label any other relevant information, such as medications you’re taking. 
• Especially if you’re going to freeze or freeze-dry your breast milk and want to remember which batch contained such medication. When freeze-drying your breast milk with Nourishy, we include all the notes you made on the back of your powder pouch.
• Pro tip: Keep multiple markers handy wherever you work with your breast milk to easily label the bags or containers.
• If your baby is being cared for by someone else, such as at daycare, a nanny or a babysitter, include:
  
  
  • Your baby's name
  • The date the milk was expressed
  • The amount of milk in the container
  • Feeding instructions (including any special heating or handling directions)
  • Any allergy information if applicable
  • Your contact information in case the caregiver needs to reach you.

One acronym frequently used when it comes to breast milk storage is FIFO. FIFO stands for First In, First Out, which is a concept originating from inventory management that is particularly useful for perishables. FIFO is a simple system to ensure older breast milk is used first, before newer milk. AKA the milk you put in your fridge yesterday should be used first, before the milk you put in your fridge today. The FIFO method helps prevent waste while keeping your stash in your fridge or freezer organised. 

 

 

Breast Milk Storage Guidelines Made Simple

The big question is always “How long can my breast milk sit out?”. You can store breast milk at room temperature, in the fridge, or freezer, depending on how soon you’ll use it. It’s always the easiest to think of the 4-4-6 Rule of Breastfeeding:

• 4 hours at room temperature
• 4 days in the refrigerator
• 6 months in the freezer

The 4-4-6 Rule is a general guideline to help parents remember storage duration, still, it’s always best to adjust to your environment if temperatures outside or within your fridge or freezer have changed. Always take the cautious route when it comes to your baby's nutrition, and if you think the milk might be off, rather discard it. More on what to look out for when it comes to spoiled milk is below.

 

Storage Quick Reference Guidelines 

The table is in combination with the WHO (World Health Organization3), the CDC (Centre for Disease Control4) and the NHMRC (National Health and Medical Research Council2). We’ll always recommend first consulting with your health care provider or lactation specialist for your own personal requirements and environment.

 

 

Storing Breast Milk at Room Temperature (26°C or lower)

• Do use milk within 4-8 hours when stored at room temperature
  
• Do transfer milk to the fridge or freezer if not used within 4 hours.
  
• Do store milk in a shaded, cool spot to maintain freshness.
  
• Don’t leave milk in direct sunlight or near heat sources like ovens.
  
• Don’t rely on room temperature storage during heatwaves; do use an insulated cooler with ice packs instead.
  
• Do follow the "first in, first out" (FIFO) method to use the oldest milk first.
  
• Do keep containers closed and avoid transferring milk between them to reduce contamination risk.

 

Storing Breast Milk in a Refrigerator (5°C or lower)

• Do use milk within 3-4 days of refrigeration. 
• Do store freshly expressed milk in a refrigerator at 5°C or lower.
• Do move freshly expressed milk into the fridge as soon as possible, if it’s not going to be used within 4 hours.
• Do freeze milk that won’t be used within 2 days of refrigeration.
• Do place milk containers at the back of the fridge for the most stable temperature.
• Don’t store milk in the fridge door to avoid temperature fluctuations that can occur with frequent opening.
• Do follow the "first in, first out" (FIFO) method to use the oldest milk from the fridge first.
• Don’t mix warm freshly expressed milk with already chilled milk, cool it in the fridge separately first to prevent bacterial growth.

Storing Breast Milk in a Freezer (-18°C to -20°C)

• Do use milk within 6 months of freezing. 
• Don’t use milk that was stored in the freezer for more than 12 months, as the nutritional quality may decrease slightly over time.
• Do use breast milk storage bags designed for freezing to prevent leaks.
• Don’t overfill containers or bags; leave 2-3 cm of space for expansion during freezing.
• Do store milk at the back of the freezer where the temperature is most stable.
• Don’t store milk near the freezer door to avoid temperature fluctuations that can occur with frequent opening.
• Do store freshly expressed milk in a new or sterilised container instead of mixing it with previously frozen or refrigerated milk.
• Do follow the "first in, first out" (FIFO) method to use the oldest milk from the freezer first.
• Don’t refreeze thawed milk; use it within 24 hours.

Storing Thawed or Previously Frozen Breast Milk

• Do thaw frozen milk in the fridge overnight or place the container in a bowl of warm water.
• Don’t thaw milk at room temperature to avoid bacterial growth.
• Do warm milk gently using warm water, not a microwave, to preserve nutrients and prevent hot spots.
• Don’t refreeze thawed milk once it has been thawed.
• Do swirl the milk to mix the fat layer before feeding and test the temperature on your wrist.
• Do use thawed milk within 24 hours if stored in the fridge.
• Do keep thawed milk at room temperature for up to 4 hours until the next feed, then discard.

 

Storing Your Breast Milk in Powder Form

• Do keep your Nourishy breast milk powder pouches sealed and in a cool, dry indoor location.
• Don’t store your breast milk powder in vehicles, garages, or outdoor areas.
• Do keep the pouch in a cool, dry place with the zipper securely closed after opening your pouch.
  
  
  • Single-Use Pouches: Discard unused powder after 5 days.
  • Multi-Feed Pouches: Discard unused powder after 30 days.
    
    
• Do discard of the entire pouch if moisture is introduced at any point.
• Do keep the powder scoop in a clean, dry place outside of the pouch between uses.
• Don’t use if the expiration date printed on the custom label has passed.

 

Advice on Mixing and Handling Breast Milk

As we know by now, mixing and handling breast milk correctly is essential for maintaining its safety and nutritional quality. Whether you're combining milk from different pumping sessions or preparing it for storage, following proper techniques ensures your baby receives the best possible nourishment. Here’s what you need to know to handle your breast milk confidently and provide safe, nutritious feeds for your little one.

Tips for Mixing and Handling Breast Milk:

• Seal Containers Properly: Ensure all containers are securely sealed to prevent contamination.
• Avoid Overfilling: Leave 2–3 cm of space in containers or storage bags to allow for expansion during freezing.
• Store Smaller Portions: Freeze milk in small quantities (60–120 ml) to minimise waste and simplify thawing. Always check breast milk bag capacity sizes - some bags have a capacity of 120ml, while others can take up to 200ml or more. You’ll know your baby best and how much milk gets consumed in one feeding.
• Do not overfill containers or bags: Leave about 2-3 cm of space at the top, as breast milk expands when frozen.
• Cool Before Mixing: Always cool freshly expressed milk in the fridge before combining it with already chilled or frozen milk.
• Avoid Mixing at Different Temperatures: Never mix warm milk with chilled milk to prevent bacterial growth.
• Warm Milk Gently: Place the container in a bowl of warm water or use a bottle warmer, and avoid microwaving to preserve nutrients.
• Check Before Feeding: Test the milk on the inside of your wrist to ensure it’s lukewarm, and not hot.

 

  

Travelling and Storing Breast Milk On-the-Go

For busy parents, travelling or working while breastfeeding can sometimes feel stressful. But whether you’re commuting, working from the office or taking a flight, with proper storage techniques, you can safely manage your breast milk no matter where you go. 

 

Tips for Travelling and Storing Breast Milk:

• When travelling with breast milk: Use an insulated cooler with ice packs to maintain milk freshness during transport.
  
• When at work: A mini fridge is perfect for discreetly storing milk at the office, but if you don’t have access to a mini fridge at work, use an insulated cooler bag with ice packs in the communal fridge or at your desk. If you use a communal fridge your milk is accessible from a communal fridge, clearly label your containers and ask your manager to re-emphasise office fridge rules of respecting each other’s food and drinks - we’ve all heard a crazy story or two about a co-worker accidentally using breast milk in their coffee.
• When flying with breast milk: Most Australian airports allow you to carry breast milk in reasonable quantities with or without your baby present. According to the Australian Breastfeed Association (ABA)5, for domestic flights, there are no restrictions on breast milk or baby items unless connecting to an international flight. For international flights, a reasonable quantity of liquids, aerosols, or gels is allowed for a baby. When travelling without a baby, in a carry-on bag, you can carry expressed milk in 100ml containers (up to 1 litre in total). And for checked-in baggage, larger volumes of expressed milk can be packed in an insulated container without restriction. Please confirm specific guidelines with your airline before you travel.
• When to freeze-dried breast milk for travelling: Freeze-dried breast milk makes travel easier by eliminating the need for refrigeration while preserving nutrients, offering an innovative solution for mums and dads on the go. Not only does freeze-drying help that you don’t need to travel with ice packs, but it also saves space in your suitcase. Find out more about how Nourishy can help you with your travel needs.

 

Recognising Spoiled Breast Milk

When breast milk is your baby’s primary source of nutrition, you want peace of mind that your baby is getting the best and freshest milk. Even if you take care in properly handling and storing your breast milk, spoilage can still happen under certain circumstances. 

Signs of Spoiled Breast Milk

• Exceeding General Safe Storage Times:
  Consider breast milk as no longer safe if it has been left at room temperature for more than 4–8 hours, stored in the refrigerator for over 4 days, or thawed from frozen for more than 24 hours.
• Look for Changes in Appearance: 
  Some fat separation in breast milk is normal, especially if your milk has been in the fridge for a few days, but this can be resolved by gently swirling the milk. However if the layers don’t mix back together or the milk appears curdled discard the milk.
• Watch for Color Changes: 
  Breast milk can vary slightly in colour depending on your diet, but any drastic or unusual discolouration could indicate spoilage.
  
  

How to Test Freshness

• Perform a Smell Test: 
  Sniff the milk before feeding to ensure it smells fresh and pleasant. Fresh breast milk has a mild, sweet smell. If it has a sour or rancid odour, it’s likely spoiled.
• Conduct a Taste Test: 
  If the milk smells fine but you’re unsure, taste a small amount. Spoiled milk will have a sour or off-putting taste.
  
  

What to Do with Spoiled Milk

• Discard Immediately: 
  We know it’s hard to sometimes discard your breast milk, especially for mums who might have a low supply. However, if the milk shows any signs of spoilage, it’s important to throw it out to ensure your baby’s safety. Alternatively, you can use any safely stored breast milk for a baby’s bath, as it can have soothing properties for their skin.
• Inspect Storage Practices: 
  Check that your fridge or freezer maintains the correct temperature, and review handling techniques to prevent any future spoilage.

 

Special Tips for Our Aussie Parents

Australia’s warm climate means that breast milk storage requires extra care to ensure your baby’s milk remains safe.

Keeping Milk Fresh in a Warm Climate

• Inspect Your Fridge and Freezer Ahead of Time: Before your baby arrives, check your fridge and freezer for any broken seals or poor insulation. If repairs or upgrades are needed, add this to your baby checklist and consider asking for gift cards if possible or saving up for replacements to ensure proper milk storage.
  
• Refrigerate Immediately After Pumping: To reduce the risk of bacterial growth, transfer freshly expressed milk to the refrigerator or freezer as soon as possible.
  
• Store Milk in the Back of the Fridge or Freezer: The back of the fridge or freezer maintains more consistent temperatures compared to the door, where fluctuations are common.
  
• Invest in High-Quality Cooler Bags and Ice Packs: Choose durable, insulated cooler bags and effective ice packs to keep breast milk fresh during warm summer months. Use it whenever you’re transporting milk — whether running errands, commuting, or moving milk to or within your home — to maintain a stable temperature when refrigeration isn’t immediately available.
  
• Consider Freeze-Drying Your Breast Milk: Freeze-drying is an innovative way to save freezer storage. Freeze-dried breast milk can be safely stored in a cool, dry place like a pantry, offering a convenient and space-saving alternative to traditional freezing.

 

Coping with Unplanned Events

• Prepare for Power Outages: Keep cooler bags with ice packs ready as a backup during power outages to store milk safely. Avoid opening the fridge or freezer unnecessarily to maintain the internal temperature, and use a thermometer to monitor if milk has stayed within safe ranges. Milk that remains partially frozen or cold to the touch is still safe to use.
  
• Heatwaves and Extreme Temperatures: Ensure your fridge and freezer can maintain safe temperatures during extreme heat.
  
• Bushfires and Emergency Evacuations: Be ready with portable storage solutions in case you need to leave your home quickly.
  
• Flooding or Cyclones: Protect your milk supply by having backup storage plans for severe weather events, such as flooding or tropical cyclones.

 

Exploring Milk Banks and Community Resources

• Consider Milk Banks: If you’re interested in donating or receiving breast milk, look into local milk banks. They provide a safe, regulated way to share milk with babies who need it.
  
• Access Community Support: Reach out to lactation consultants or breastfeeding support groups for additional guidance on milk storage and handling in Australia’s unique climate.
  
  

Storing breast milk doesn’t have to be daunting. With these simple steps and tips tailored for Australian parents, you can keep your milk safe and nutritious for your little one. Remember, if you’re ever in doubt, consult a lactation consultant or trusted healthcare professional.

 

Frequently Asked Questions

Here are answers to a few common questions and answers:

Can I mix milk from different pumping sessions? 
Yes, but cool freshly expressed milk in the fridge before combining it with already chilled milk.

Can I refreeze thawed milk? 
No, thawed milk cannot be refrozen and should be used within 24 hours.

Can I save breast milk that my baby didn't finish? 
No, leftover milk should be discarded after 1–2 hours to prevent bacterial growth.

Can I store breast milk in bottles instead of bags? 
Yes, but bags are more space-efficient for freezing.

Can you put breast milk back in the fridge after taking it out? 
Yes, if it hasn’t been warmed or sat out for more than 2 hours.

Do I have to throw away frozen breast milk if the power goes out? 
Milk is safe if it remains partially frozen or cold to the touch. Otherwise, discard it.

How long can breast milk sit out before it goes bad? 
Breast milk is safe at room temperature for up to 4 hours (or up to 8 hours in cooler conditions).

How long can colostrum be at room temperature? 
Colostrum can be safely stored at room temperature for up to 12 hours.

How much milk should I store for emergencies? 
Aim for a week’s supply, based on your baby’s feeding needs.

How will I know if breast milk is bad? 
Look for a sour smell, unusual colour, or separation that doesn’t mix when swirled.

What happens if a baby drinks old breast milk? 
Old milk may upset your baby’s stomach or cause mild illness. Discard milk if you’re unsure.

What’s the best way to transport milk to daycare? 
Use an insulated bag with ice packs and ensure it’s refrigerated upon arrival.

 

References

1. National Health and Medical Research Council (NHMRC). (2012). Infant feeding guidelines. Retrieved from https://www.nhmrc.gov.au/health-advice/public-health/nutrition/infant-feeding-guidelines 

2. National Health and Medical Research Council (NHMRC). (2012). Infant feeding guidelines: Information for health workers. Retrieved from https://www.nhmrc.gov.au/about-us/publications/infant-feeding-guidelines-information-health-workers

3. World Health Organization (WHO). (n.d.). Handout: Hand Expression And Container. Retrieved from https://cdn.who.int/media/docs/default-source/mca-documents/nbh/enc-course/revised-resources/supplemental-materials/breastfeeding-overcoming-difficulties/handou-1.pdf?sfvrsn=dd0d3352_1

4. Centers for Disease Control and Prevention (CDC). (November 27, 2023). Breast milk preparation and storage: Proper handling and storage of human milk. Retrieved from https://www.cdc.gov/breastfeeding/breast-milk-preparation-and-storage/handling-breastmilk.html

5. Australian Breastfeeding Association. (n.d.). Expressed breastmilk and air travel. Retrieved from
https://www.breastfeeding.asn.au/resources/expressed-breastmilk-air-travel