Expressing breast milk this summer? Storing it safely will protect your baby's health

The summer months are upon us and with them we’re getting the usual food safety reminders. Be careful handling raw meat when preparing for your backyard barbecue, refrigerate the potato salad, and so on. These tips are designed to protect us from food poisoning, an unwanted addition to anyone’s summer holiday.

But few people are likely to consider the issue of food handling for babies: in particular, of expressed breast milk. Parents who use expressed breast milk are routinely transferring it between containers, defrosting it, and reheating it.

Breast milk is a raw animal food product. It contains live cells, proteins, carbohydrates, fatty acids, micronutrients, probiotics, and more. But the health-giving properties of breast milk decrease over time. And while breast milk has properties which inhibit the growth of some harmful bacteria, factors such as heat and time can enable these harmful bacteria to grow.

Read more: Want to breastfeed? These five things will make it easier

From breast, to bottle, to bub

The World Health Organisation recommends feeding babies breast milk exclusively for the first six months of life. So for many babies, this is their only source of food.

Up to 98% of breastfeeding women will express milk at some stage. Mothers may express milk if they are leaving their babies with partners, relatives, or babysitters. Planning to drink alcohol is another common reason women express milk ahead of time.

Some mothers only express and never directly feed: around 4% of breastfeeding women in Australia and up to 18% elsewhere. Mothers may exclusively express if their baby is not able to feed (because of a mouth malformation, poor latching, or breast refusal), if returning to work, or for other reasons.

If you’re using expressed breast milk to feed your baby – whether you do it all the time or it’s just a once off – here’s what to keep in mind.

Read more: The National Breastfeeding Strategy is a start, but if we really valued breast milk we'd put it in the GDP

Preparation for expressing

• Wash hands with soap and water (or hand sanitiser) every time, and dry on a clean cloth (or paper towel)

• equipment and storage containers should be washed with warm soapy water and air dried (or dried with a paper towel).

Storage

Like other food products, the length of time for which you can safely store breast milk will depend on where you store it – whether at room temperature, in the fridge, or in the freezer.

Storage guidelines based on the most up-to-date evidence are published by the National Health and Medical Research Council.

We’ve summarised this information in the table below, where the “ideal limit” will ensure the milk keeps its nutritional value, and the “maximum limit” is the time period which should not be exceeded for safety reasons.

The advice for room temperature does not apply for environmental conditions over 26℃. It’s important to immediately refrigerate or freeze any expressed milk in temperatures above 26℃.

One study looked at storing breast milk in ice-packed coolers, for example a small styrofoam box packed with “blue ice” (the ice packs designed to keep food cold). This study found breast milk could be safely stored in this way for a maximum limit of 24 hours. This may be useful when parents need to store breast milk on the go, but this method of storage requires further research.

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Feeding

• Ideally, thaw breast milk in the fridge and use it within 24 hours (you can also thaw it in a container of warm water for immediate use)

• nutrients are best maintained under 37℃. Warm the breast milk by putting the bottle in lukewarm water (less than 40℃) for up to 20 minutes. Avoid the microwave for heating because it has the risk of hot spots (overheated sections of the liquid, like when you microwave a meal and some bits are hotter than others)

• you can offer cool, room temperature, or warmed milk to the baby

• discard any unused remains after a feed.

The guidelines aren’t always clear

In our recently published research, we reviewed the online guidelines around handling and storage of expressed breast milk accessible to Australian women. We found a lot of conflicting advice, which can be confusing for mothers.

Considering breast milk is the only source of food for many young babies, the number of mothers who express, and the future trend toward milk banking, more research needs to be done into the physical properties of breast milk, and its safe handling and storage.

Read more: Breast milk banking continues an ancient human tradition and can save lives

The authors would like to acknowledge the contributions of fellow team members Hayley Scott and Leah Strauch.