How to store breastmilk?

Question

I am a working mom and I intend to express milk at my office say by around 11.30 and by 2. I am staying in India, Bangalore.

1. Now, can I mix the milk expressed these two times if they both are at room temperature?
2. Can I refridgerate this combined milk after coming home (by around 3 pm)?
3. Can this milk be used to feed my baby the next day when I am out to office again? (before 36 hours of time of expressed milk)

Answer 1

If I do a quick math of the recommended storage times¹, then probably yes, but you could be getting very, very close to the "unsafe" threshold.

What you should change or eliminate is the storage and transport at room temperature part, because that will be the time of fastest bacterial growth. If you have access to a refrigerator at work, put your milk in it to cool it down quickly. If that's not possible, you'll need a form of insulated bag or container and ice packs. This will also be handy to transport the milk home - Bangalore can be quite hot, as we all know.

Mixing the milk is not really a problem, especially if you are pumping just for the next day, not for long-term storage. But make sure that whoever handles it does not warm the entire batch, just enough for one feeding. This is one of the reasons I personally preferred to store "single servings".

And especially where babies with their sensitive digestive system and breast milk are involved, it is better to be on the safe side...

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¹
Using the numbers from the CDC, cited here:

1. 11:30 to 3:00 -> 3.5 hours or 7/12 of the 6h at room temperature window.
2. This leaves 5/12 of the 5 days in the refrigerator, i.e. 50 hours.

Going by the (larger) numbers quoted here:

1. 11:30 to 3:00 -> 3.5 hours or 7/12 of the 6h at room temperature window.
2. This leaves 5/12 of the 4 days in the refrigerator, i.e. 32 hours.

Of course both numbers are estimates, so use common sense and cool the milk if possible.

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Some recommended background reading on food safety from our sister site Seasoned Advice can be found here.

Answer 2

1. It is not preferably to mix breastmilk expressed at different times, since the lifetime of both quantities will differ. Plus the expressed milk comes out warm, around 37°C and it is also not recommended to mix breasmilk at different temperatures then refrigerate it.

2. Due to the CDC Website breastmilk is safe for 6-8 hrs at room temperature which is equivalent to 25°C.

So probably the milk you expressed at 11:30 should be still safe for your baby till you refrigerate it at home. To take more precautions you can place it in an insulated cooler bag to increase its lifetime in case you are not able to refrigerate it.

To be more sure your baby is drinking safe milk, someone can taste it before offering it to him. If it tasted bitter then it is spoiled. Babies almost know to taste, and he shall refuse it if it tasted bad. These are some steps to check the spoilage of milk.

3. Once refrigerated, then the milk will be safe till 3 days at least. Then yea your baby can take it the next day.