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Sluggish Fermentation Woes

TroubleShooting

Charles Rizzo — Bensenville, Illinois asks,
Q

Last spring I purchased some Sauvignon Blanc juice made from Chilean grapes (Brix was 24.5, pH was 2.95, TA was 0.45, and the temperature at the time of receipt was 40 °F/4 °C). The product seemed to be in fine condition; no swelling of pails from fermentation, good smell, color etc. I allowed the juice to warm overnight to 60 °F (16 °C) and inoculated with QA23 yeast following the recommended technique of hydrating and feeding with Go-Ferm and began fermentation. Four months later, the wine was at -0.01 °Brix (still fermenting). I added Fermaid K at the recommended level and time. I even bumped the temperature to 75 °F (24 °C). Why did the fermentation take so long? I believe the grower/processor did something to retard fermentation during shipping. What would they have done? The numbers seem strange also, I usually work with fresh fruit and normally see the pH around 4 to produce a TA of 0.45 (at pH 2.95 I expected TA 0.7+). This wine doesn’t fit my past experience and I am looking for answers. I hope
you can help.

A
Hmmm, it sounds like you’ve got a little bit of sugar left there. I would start, however, with a quick check of your numbers to be sure. A °Brix of -1.0 (0.995 specific gravity) is where “dryness” starts when measuring with a hydrometer. Please make sure you are temperature-correcting your hydrometer reading. If your juice/wine is too warm, the hydrometer will sink more than it should because the wine is less dense than it would be at colder temperatures and will show an artificially high Brix reading. Hydrometers are calibrated for 68 °F (20 °C), and you will need to add or subtract to your reading when the wine’s temperature is on either side. You can find online hydrometer corrector calculators, which will also handily help you compensate for the increased alcohol level, based on your original Brix. You should also try running a Clinitest trial, which will give you an estimate of the residual sugar you have left (to learn more about this method, check out the “Techniques” column “Measuring Residual Sugar” from the April-May 2002 issue of WineMaker).
Response by Alison Crowe.

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