Malic acid
DL-malic acid
Raises acidity with a sharper, greener sourness than tartaric.
Typical dose
Comparable to tartaric by weight; bench-trial. Do not use in a wine that will undergo malolactic fermentation.
When to add it
Finished wine, once malolactic has been ruled out or blocked.
In practice
Sharper on the palate than tartaric, and food for lactic bacteria. Add it to a wine that later goes through malolactic and the bacteria eat it straight back out, undoing the addition and raising volatile acidity on the way. Reserve it for wines already stabilised against malolactic.
Linked faults are the ones this addition either treats or, used wrongly, causes. The fault page says which, and whether it can be undone.
Others in acids and deacidifiers
Tartaric acid
Raises acidity and lowers pH using the acid grapes already contain.
Citric acid
Small acid corrections and iron-haze prevention, but microbially unstable.
Lactic acid
Gentle acidity for fine-tuning, especially after malolactic.
Potassium bicarbonate
Deacidifier: lowers titratable acidity and raises pH.
Calcium carbonate
Deacidifier for large acid reductions, via the double-salt method.
Potassium carbonate
Deacidifier, stronger per gram than the bicarbonate.