Glossary
Malolactic conversion
A secondary process — not a fermentation in the yeast sense, despite being commonly called malolactic fermentation — in which lactic acid bacteria convert malic acid into lactic acid. It lowers acidity, softens texture and can produce diacetyl, which smells of butter.
In more detail
Almost all red wine goes through it. For whites it is a choice: full conversion gives buttery Chardonnay, blocking it keeps the wine sharp.
The buttery character people associate with Chardonnay comes from here, not from the grape or from oak.