Ask Wine Wizard

Post-Fermentation Wine Acid Adjustment


Clay Johnson — Leavenworth, Washington asks,

My 2021 Merlot (I’m up in Washington State) finished out fermentation with a pH of 3.85. I added some tartaric acid (about 0.5 g/L) right before fermentation, but that pH is a little higher than I’d want. Is it OK to add tartaric acid after fermentation? Any tips on how to do it so I don’t overdo it?

Great topic and great questions. If you’ve read my columns over the years, you’re familiar with my mantra of acid being the “backbone” of wine, as well as the importance of having the correct pH for long-term aging. The higher the pH (lower acidity), the more spoilage organisms like Lactobacillus and Acetobacter can get a foothold and perhaps eventually spoil your wine. Additionally, having a higher acid level helps your free SO2 additions be more effective; the lower the acid level, the more SO2 you must add for a comparative efficacy. Post-malolactic fermentation (MLF) I like to keep my red wines below 3.65 pH and my whites below 3.5. Oftentimes, as you know, the pH will creep back up after primary fermentation or, post-press, will be much higher than you anticipated, even with a pre-fermentation acid addition. This is extremely normal and happens even to professional winemakers (shhh, just don’t tell anyone!). Because post-primary fermentation pH is really hard to predict, tweaking that pH back down with a little tartaric acid can be just the ticket. Here’s how to plan
Response by Alison Crowe.