there are some commercial brands of ghee which claim to be absolutely free of milk protein - and indeed, I bought one of them and tolerated it well even in large amounts (I have an IgE mediated allergy to milk protein). Unfortunately it's quite pricey and so I wanted to make my own clarified butter.
I carefully followed the instructions and after the butterfat was completely clear I poured it into a coffee filter. The resulting liquid had no obvious impurities and I left it to cool. It tasted terrific but my stomach got really angry afterwards.
The question is: How do commercial ghee producers manage to clear their ghee in such a way, that even trace amounts are filtered out. What can I do to make such a pure butterfat myself? Any ideas how to clarify the clarified butter?