Fall in Our Vineyard

It seems that all is calm and quiet in the vineyard but, our hunter friend recently sent us some photos that he took when he saw a bobcat in the vineyard.

Racking Off the Gross Lees

At the end of our fermentation we consolidated our newly made wine from the two kegs that we had it in during fermentation into one keg. My husband purchased all of the equipment, nitrogen gas, regulator, racking wand, etc.
Since the pH, titratable acidity and sulfur dioxide values were very similar in the two kegs, we felt that we could combine it without unduly affecting any of the parameters. We let the wine settle in the one keg. What we hoped to accomplish with this step was to settle out the yeast that were floating around in the fermentation.
We left the tank in the refrigerator from Friday, October 23 until Tuesday, October 27 to allow the yeast and other large particles of fermentation to settle out of solution. We used the same setup with nitrogen gas to rack over just the clarified wine. It was a tricky little maneuver because we only had visual cues to guide us in determining when to stop racking. We think we did a pretty good job. When we went to empty what remained in the bottom of the fermentation tank, we decanted over some pretty gross lees, shown at the left in the photo and we took out about 10 mL of wine in order to do more tests, including a sensory (i.e. tasting) test.

Unfortunately, I messed up the titratable acidity test, but our sensory exam leads us to believe that our wine is still searingly acidic.

Our Fermentation is Over

On Friday, October 23, we checked our fermentation by running a few tests using our Vinmetrica SC-300 Pro. We tested the Vinmetrica system using a wine we had on hand so we were reasonably confident that our technique could be used to test our wine. There are online videos provided by Vinmetrica that give step-by-step instructions on the following:

• How to Calibrate the Vinmetrica SC-300 Prior to Making pH and Titratable Acidity (TA) Measurements
• How to Measure the pH
• How to Take a Titratable Acidity Measurement
• How to Take an SO₂ Measurement

On this fateful day, we conducted our tests on the juice in the two kegs that had been fermenting since September 30th. Our last reading that we took on October 13th gave us a Brix reading of 9. We ran the tests on our fermentation including the Accuvin Residual Sugar Test and we found that we had the following values:

• pH = 3.15
• TA = 12.25 g/L
• SO₂ = negligible
• Residual Sugar = ~500 mg/L

We stopped the fermentation by adding potassium metabisulfite into our two kegs. I used the: Sulfite Calculator
to determine that we needed to add 1 gram of potassium metabisulfite to achieve the required 0.825 mg/L molecular sulfite level.
We had hoped to leave a little residual sugar in our wine, but the values indicated that we had far over shot our mark. We also have a lot of acidity, some might call it searingly acidic. We are hoping that our tartrate stabilization might take out some of the titratable acidity and lower the TA a little.
We are consoling ourselves with the good news.

• First, our fermentation was long and slow and we didn't run into any problems with a stuck fermentation, indicating that our fruit came in with enough food for the yeast.
• Second, we didn't have any volatile acidity (acetic acid) issues, or fingernail polish (ethyl acetate) issues, or rotten egg (hydrogen sulfide) issues.
• Third, we have approximately 5 gallons of wine from the 65 pounds of fruit that we harvested.
• And last by not least, we learned a lot and hope to apply this knowledge into configuring a working lab and getting the appropriate equipment for scaling up to a full harvest, hopefully in the near future.

Steps to Consider After Fermentation is Over

Measuring Residual Sugar
So far, we have managed to conduct a constant temperature (60^o Fahrenheit), slow fermentation, resulting in a decrease of 1 ^oBrix a day. We are approaching the end of the fermentation and we are giving careful consideration on how to proceed. When the fermentation was evolving a lot of carbon dioxide, we felt comfortable in opening the fermentation lock to check on the Brix, but now, with most of the sugars converted to alcohol and the carbon dioxide evolution is on the decline, what do we do?
We want to make wine in the style of Domaine Huet and we found a Domaine Huet Fact Sheet published by Europvin. In that fact sheet is the following information:

• Sec: 11.5 - 12% alcohol; 3 - 5 g/L residual sugar
• Demi-Sec: 12 -13% alcohol; 10 - 20 g/L residual sugar
• Moelleux: 13 - 14 % alcohol; at least 30 g/L, but can be anything up to 200 g/L residual sugar

Vinification of the Chenin Blanc grape is about the proper balance of alcohol, acid and residual sugar. Without some residual sugar, the acids take over, so we do want to have a bit of residual sugar in our wine.
To measure the sugar left in our fermentation, we purchased the Accuvin Residual Sugar Test to get an approximate idea of how much residual sugar we have that is below the level of 1 ^oBrix since:
1 ^oBrix = 1% sugar (wt/vol) = 1 gram sugar/100 mL = 10g sugar/1L
The range of the test goes from a low of 100 mg/L to 2000 mg/L and if we want to test for 5-8g/L (5000-8000mg/L), we would have to do some dilutions:

Stay tuned!
References:
1. UC Davis Online Course: Wine Production, VID252, Lesson 3, page 6.
2. Daniel Pambiachi, Measuring Residual Sugar: Techniques, WineMaker, April/May 2002.