I’m putting together a seminar on wine fermentation for my company’s lunchtime science lecture series (tomorrow) and am a little confused on volatile acidity limits and measurements. The UCD page on VA says that VA includes not only acetic but also lactic (and butyric, propionic etc), and the US legal limits are 1.1 - 1.2 g/L - but lactic is often above this level if you do ML fermentation, right? So even though lactic is defined as a VA does it not count against the limit? Thanks!
Tartaric and malic acids are ‘fixed’ (aka non-volatile) acids.
Acetic acid is the main volatile acid, of course…along with others (butyric, formic, etc), and are what is measured for VA tests.
Lactic, succinic and sorbic are slightly volatile…because of this (being only slightly volatile), they aren’t counted when determining VA.
Note also that EA (ethyl acetate) is an ester of acetic acid and ethyl alcohol. When a wine has acetic, a portion of it is converted into EA. But, because EA is an ester, not an acid, it isn’t included in VA tests (EA generally exists at very very low levels tho, so the VA results wouldn’t change much anyways). When a wine smells of VA, generally you’re smelling the EA more than the VA.