Childhood Diseases

Posted by: Jacaranda | 2010/10/28


Freezing Milk

Hello Professor,

I have heard that it is bad to microwave baby bottles with milk in them as the plastic releases cancer type toxins.

Is this also true to freezing milk? I would like to freeze some milk for my baby in a plastic bottle.

Expert's Reply



Most of the new baby bottles are said to be free of BHA which is the chemical which leeches out when the bottle is warmed or frozen. Make sure that your baby's bottles are free of BHA. They should have a symbol underneath stating that they are free of BHA.

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user comments


Posted by: Purple | 2010/10/29

Check underneath the bottle, the bottles with BPA have a number 7 on them - these are the ones that you should rather not use at all, but yes, the problem is indeed when the toxins leach into the milk when the bottle is heated (microwave, bottle warmer etc).

Don''t freeze milk in a bottle, rather sterilise ice trays (the kind with lids), each block is around about 20ml. When the tray is full, transfer the blocks to a zip lock bag which you date with the date of the oldest milk. You can keep the milk in the freezer for up to 6 months.

When you want to use the milk, put the number of ice blocks needed into a bottle and let it defrost slowly by standing it in a bowl of luke warm water or just standing it on the kitchen counter. Once defrosted, the best way to warm the milk is in a bottle warmer. Never leave it for long periods, put it in just before you need to use it.
As bottles are made of fairly brittle plastic, the freezing and defrosting could crack the bottle, as the milk expands when frozen and contrcts when warmed up (or the other way around, but either way, it changes in volume and can crack the bottle, which doesn''t expand and contract with the changes in temperature).

Using the blocks like this means you won''t waste any milk as you just defrost what is needed, and if you need more, you just defrost another block or two. The milk defrosts quite quickly.

Reply to Purple

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