Ask Wine Wizard

Sluggish Fermentations — Cabernet Franc


Stan Sowinski — Falls, Pennsylvania asks,

I’ve got a reoccurring problem with my estate red wines. For the past two years my Cabernet Franc fermentations have been stalling out when the specific gravity (S.G.) hits 1.000. Malolactic (ML) culture is added at this point and it does complete within a few weeks. Fearing spoilage problems, I added SO2 shortly after ML completion (based on pH using WineMaker’s sulfite calculator.) I started with an initial S.G. of 1.023, pH of 3.41 and titratable acidity of 6.4. I used D-254 with a properly prepared yeast starter and the maximum recommended amount of DAP and yeast nutrient, and fermented between 65-75 °F (18-24 °C). Secondly, It has been two months since the primary fermentation. Is it too late to re-ferment this batch of 35 gallons (132 L) of Cabernet Franc? What are the possible consequences of adding new yeast and nutrients at this point? It has been racked one time and has minimal lees.


See my response here regarding general information about stuck and sluggish fermentations. Your wine is a lot closer to dryness (essentially 0 °Brix) than the previous reader’s sweetest lot, so I don’t know if I would recommend a re-start. When I’ve attempted re-starts below 0 °Brix, the extra added yeast and nutrients just make the mouthfeel and the nose of the wine “off.” Sometimes, I’ve even ended up with higher residual sugar than my initial batch!

The small amount of residual sugar you have may be enough to blend down if you think the wine is too sweet, if you have other wines that you can blend with it. You could try a re-start (see suggested resources on page 16) but I’m not sure I would recommend it.

You certainly want to try to focus on prevention, and on “checking all the boxes” that I list in the first answer. Your yeast choice, D-254, can safely ferment up to 16% alcohol, so your initial Brix of 23 should not have been a problem. All of the adjustments you did sound fine to me.

There are two things that strike me in this situation, however. Sometimes if malolactic fermentation (ML) happens concurrently with primary, the “bugs” (bacteria and yeast) all can compete for resources with each other, and one or both may be in danger of sticking. For this reason, I always choose to try to have primary fermentation finish before inoculating the wine with my ML strain. Try adding Lysozyme/Lactizyme (10-20 g/hL is what the manufacturers recommend) to your must in order to retard any wild ML strains that may want to gain a foothold, and inoculate with ML bacteria only after primary is complete.

You also may want to keep your fermentation on the skins a bit longer. Sometimes when pressing off with residual sugar still in the must (sometimes pressing itself releases latent sugar in the grape skins), the temperature drop from a warm, happy must to a cold press and stainless steel tank (or even “cold” barrel or carboy) can shock the yeast into slowing down or stopping. You may want to run a Clinitest® test or send out a wine sample to a wine lab to get an exact measurement of where you are. Sometimes S.G. and Brix at these low ranges can be tough to read accurately, especially if you are not using a hydrometer with a wide enough scale. Good luck!


Response by Alison Crowe.