OK. Slightly random question, but I have wondered about this for ages.
When I defrost my expressed breastmilk it always smells different to the freshly expressed stuff. When I give it to my baby she always pulls a face as if it is not v nice (but she might just not like bottle).
I have heard that with some people their breast milk changes in taste after freezing.
Google 'excess lipase' in breastmilk. I have this issue - if I just freeze bm it tastes gross when defrosted. Similarly, mine only lasts about 24 hrs in the fridge before tasting horrid (and my DD won't touch it). There's a way around it - you need to scald the milk before freezing it. Sounds like a pain, but it takes about 30 secs to heat milk in small pan until you see little bubbles begin to form at edges. Then cool quickly and either freeze or put in fridge.