Today was my first real go at the chemistry aspect of winemaking. I found myself dusting off skills I haven't used since I quit taking laboratory science classes 2nd year in college. Thankfully enough of those lessons were retained in my brain for me to pull off the basics enology requires. The first batch of test to run were about as straight forward as you get: take the temperature of your wine. The differences between the different size fermenters surprised me. The 32 gallon fermenter was 65 degrees F, the 20 gallon was slightly cooler at64 degrees and the 5 gallon came in at a downright frigid 59.5 degrees F. Considering all three are within a few feet of each other in my garage the disparity caught me off guard. Looks like I'll need to track the progress of each fermenter separately.
Next part of the wine that needed analysis is the sugar level. This is accomplished with a hand tool called a hydrometer. The hydrometer uses the density of the water to determine what the percentage sugar is, which is then translated into degrees Brix. I pulled a cup of juice from each fermenter and placed it in the sanitized test tube. Give the juice a moment to let the bubbles disperse and then gently drop the hydrometer into the juice. The hydrometer should float so that the narrow end is extending above the surface of the liquid, the level of the liquid should indicate on the scale what the percentage sugar is. The results came back at 18% from the 32 gallon fermenter, 17.5 for the 20 gallon fermenter and 18.5 for the 5 gallon bucket. There is still one more calculation to make. Since the hydrometer is calculated to 60 degrees F, and none of the juices tested were at that temperature, a little tweaking formula needs to be used. For ever degree above 60 degrees F add .03 to the Brix. Conversely for every degree below 60, subtract .03 Brix. Thus the final totals weren't substantially altered, but we're shooting for extra points for accuracy. Final total for the 32 gallon fermenter is 18.1 Brix, the 20 galloner is at 17.6 Brix and the 5 gallon fermenter's temperature difference gets rounded to 0 so the result remains 18.5 Brix.
The Last test for the day is the acid test. We did not get an acid test reading from the vineyard, so this one is our first reading of the acid level. We did get a pH reading, but the acid level and pH can differ enough to want to check both. A low acid level can lead to a weak tasting wine that isn't stable enough to age. Not something we want to deal with. If we're going to raise the acid level, now is the time to do it. All it takes is the right set of chemicals, a little juice and a steady hand with the titration.
First step in the process is to get yourself a acid test kit. Next you need 5 mL of juice to test. This measurement is important since the quantity of juice is a constant in the titration formula. Off a little bit in either direction will skew your reading high or low.
Add a little water, since the red of the juice will will mask the color change that will indicate when the Sodium Hydroxide has neutralized the acids in the wine. The last prep step is to add a few drops of the Phenolphthalein indicator. The indicator causes the color change when the pH of the solution hits 8.20.
Again precision when working with the Sodium Hydroxide (NaOH) is important. Draw 10mL of NaOH into the syringe. Add a little at a time to the juice solution. Adding more than .25 to .5 mL is not recommended, since you could overshoot the neutralization point and end up with an inaccurate reading. You also want to cap the testing chamber and give a stir after each addition NaOH from the syringe. This ensures that the entirety of the mixture is being neutralized by the NaOH.
There are a few color changes to be aware of. The first one is when the pink mixture of juice and water darkens, this is not the one to concern yourself with. The color change that indicates complete titration is when the mixture takes on a green tint. 
When the green precipitate is visible immediate stop adding NaOH. Record the amount of NaOH remaining in the syringe. Then subtract that number from 10mL. That is the amount of NaOH it took to completely neutralize the acids in the juice. Then take the final number and multiple it by 1.5. This will give you the grams per Liter of acid present in the juice. In my fermenters it required 4.6mL of NaOH to neutralize the sample from the 32 gallon batch. In the 20 gallon bath it took 4.2mL. In the 5 gallon batch it only to 3.9mL. Apply the chemical reaction formula and the final numbers are 32 gallon: 6.9g/L; 20 gallon: 6.1g/L; and 5 gallon: 5.85g/L. For a dry red wine, the target acid level is between 6.0 and 8.0 g/L. Looks like we might need to add some acid to the 5 gallon batch.
That will have to wait for later. I've got a bit of clean up to do in the meantime.For a recap:
- 32 gallon - 20 gallon - 5 gallon
Temp 65 F - 64 F - 59.5 F
Sugar 18 Brix - 17.5 Brix - 18.5 Brix
Acid 6.9 g/L - 6.1 g/L - 5.85 g/L
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