hey mommy, i am assuming ur fbm meant frozen breast milk ah? maybe this link could help you. an enzyme called lipase in the expressed bm is the culprit for fishy soapy metallic tasting bm. in the end, i stopped freezing bm because my girl rejected it and i personal almost threw up myself when i thawed the fbm. so i read up abt it. u can apparently 'scald' your ebm before storing or freezing away. read more abt the process in the same link. http://www.sdbfc.com/blog/2012/9/4/battling-and-resolving-excess-lipase-in-breastmilk.html
All the best!
Regynna Lagman