Term for all acids which, in contrast to volatile acids, remain in the wine after distillation (evaporation). However, the boundary cannot be drawn exactly, as there are also "medium volatile acids". The three most important non-volatile acids are tartaric acid, malic acid and citric acid, which account for around two thirds.
Lactic acid (more volatile), galacturonic acid, gluconic acid, glucuronic acid, glycolic acid, oxalic acid and mucilaginous acid are present in smaller quantities. The quantity results from the difference between the titratable acidity determined by titration minus the volatile acids. For this purpose, the value determined as acetic acid (all volatile acids) is multiplied by 1.25 and converted to tartaric acid. Titratable acidity minus (volatile acidity × 1.25) = non-volatile acidity in grams per litre, expressed as tartaric acid. Non-volatile and volatile acids together give the total acidity. See a list of all wine constituents under total extract.
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Diplom-Sommelier, Weinakademiker und Weinberater, Volders (Österreich)