The limitation is based on thiamine. There are several sources that indicate that 25 g/hL of Fermaid-K reaches the TTBs limit for thiamine... I just can't seem to find any of those sources at the moment.
Of course, all of this only really matters if you're commercial. Nothing says that the home producer has to observe these limits as far as I know. I have been observing them... but that's just a matter of personal preference.
Of course, all of this only really matters if you're commercial. Nothing says that the home producer has to observe these limits as far as I know. I have been observing them... but that's just a matter of personal preference.