Step 13: Primary Fermentation Phase 2


Process graphic S13.png

Phase 2 of the Primary Fermentation represents the steady state and the rapid decline in the yeast population. We may need to add more nutrient supplements, and we reduce the number of daily punch-downs to 2. We also need to reduce oxygen exposure (stop macro-oxygenation). When the temperature drops we switch to heating, to keep temperature 75-85 °F. Now we watch Tannins and Bound Anthocyanins rise. The target for the Tannins is 110% of the Anthocyanin peak. The target for the Bound Anthocyanins is 20% of the Anthocyanin peak.

Here is the detail process graphic

The phase 2 punch-down process is:

  • Take the tank cover off and blow off the accumulated CO2 with a fan

  • Twice ad day, punch down the must while making sure not to crush seeds at the bottom of the tank.

  • Take tasting sample and measure chemical properties and temperature once a day.

  • Squeegee the inside walls of the tank and wipe with a paper towel soaked in KMBS solution, and, if sugar depletion is above 90%, cover the must with a new blanket of Argon because CO2 production has diminished.

Press before Fermentation is Finished?

The critical decision for the winemaker in this phase is whether to remove the skins & seeds before the fermentation is finished. Early pressing is advised when the tannin levels get too high for the desired style of wine. So we watch out for Tannin levels to rise above 110% of the previous Anthocyanin peaks. If this happens before fermentation is complete, we consider to

  • either scoop out the bulk of the skins, press them separately, pour the extracted juice back into the fermentation tank, and let the fermentation finish in the fermentation tank,

  • alternatively, press the entire must before the fermentation is finished and then finish the fermentation in the barrel without further skin and seed contact.

If Tannin levels stay below 110% of the previous Anthocyanin peak, we continue the punch-downs until fermentation is complete, i.e. Brix at -2. At that point, we will decide whether to look for further tannin extraction by extending the maceration or to go to pressing.

Dealing with Fermentation Problems

A sluggish fermentation is indicated when the daily reduction in the sugar level slows down before reaching 8 Brix or when the sugar reduction stalls entirely before reaching -2 Brix within 3 weeks of inoculation. The causes of a sluggish fermentation are the same as discussed on the previous page covering Phase 1: lack of nutrients due to the exhaustion of available supplies, toxins, volatile acidity or spoilage microbes. For these causes the remedies are the same: adding nutrients, fining with bentonite or adding Lysozyme. Alternatively a fermentation can turn sluggish in phase 2 if the fructose/glucose ratio of the remaining sugars are out of balance; in this case, reinoculation with a special yeast capable of handling fructose is recommended.

Data Management

Data Management is identical to the process in Step 12 with one exception. We measure the chemical properties twice, using both the “MUF” and the “FinW” settings on the OenoFoss equipment. The following screenshot shows the “Juice Analysis” tab for October 24, 2017, at 9 am

Input FermActions S13.png


Tracking Results for 2017

In 2018 we made the following choices: We did not apply a second batch of nutrients at the beginning of Phase 2 because we had used Microessentials which has a delayed availability. All fermentations completed except the Petit Verdot batch which stalled at -1 Brix, despite heating the musts to keep temperatures in the high 70’s. Tannin extractions never exceeded the Anthocyanin peaks, so there was no need for pressing early. We decided to delay any addition of Tartaric Acid despite the low acidity levels (pH remained over 3.6 in all 4 fermentations)

We will review the results at the end of Step 18 

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Last updated: November 10, 2018