really yellow BM from frozen

Good Morning Ladies,

This morning I thawed some frozen BM for LO and most of it looked like it usually does, a creamy white/yellow color, but part of it was REALLY golden yellow.  I thought maybe it was just the fat that had separated so I gently swirled it and went to get a nipple.  When I came back to it not even a min later the golden yellow part had separated again and was at the top of the bottle.  I smelled it and it smelled fine, I didn't get around to tasting it, but I dumped it because I've never had this happen before and it made me uneasy. 

What do you think this could be and what are the rules on using it?  It smelled fine so maybe just taste it next time and if it smells/tastes ok its fine to use?

Thanks so much!