Sugar and Acid

Time to figure out how much sugar to put in, and adjust the acidity. The place I bought the juice from kindly tests all of their juices and puts the results up online so I don't have to. The sugar level is pretty easy. You can get a pretty good idea of the sugar level by using a hydrometer to test the specific gravity of the juice. The acid is more difficult. That requires titrating a sample up to a specific pH level so you can measure how much base is needed to change the acidity. Titrating requires some equipment and chemicals that I don't have (maybe $60 worth) and is an added hassle that I don't feel like I need to do. If I were to get really serious about wine making, I'd have to get that equipment. If I remember from chemistry, titrating isn't really all that fun. Jaime begs to differ, so if it needs to be done in the future, she's the one doing it.

The test results for this years Seyval juice were posted on monday and are as follows:

15.8 Brix (Brix is just percent sugar)

1.185% total acidity

3.10 pH

It seems as though this is not a good year for the Seyval grapes. That is the lowest Brix level and the highest acidity and lowest pH out of any of the last 8 years or so that are shown on the website. Ugh. I like the idea of just leaving the juice the way it naturally is and letting the wine turn out however it turns out, but these levels are so far off the ideal that I'll definately have to do some adjusting. Perhaps when I get some more experience I'll have a better feel for when I can do that and when I can't.

The ideal Brix level (according to 101 Winemaking) is around 21-23. Yeast has the potential to turn the sugar to alcohol with a factor of about 0.575, so the 15.8 Brix means that the wine would have at most 9% alcohol, and that is if it is allowed to ferment till all the sugar is gone (0% residual sugar). Bumping up the Brix to 21 gives it a maximum possible alcohol level of 12%. So that seems like a reasonable target to shoot for. I'd like a little bit of residual sugar left, so hopefully the wine will end up with around 11% alcohol. According to the above website, 1/8lb of sugar will raise the Brix of one gallon of juice by 1.0. Then for my juice, 21-15.8 is 5.2 Brix times 6 gallons times 1/8 lbs equals 3.90lbs sugar. Thats a lot of sugar. I have corn sugar. 101 Winemaking says this is good to use because it is simple sugar (unlike cane sugar) and the powdered form dissolves pretty easily. I guess Jaime's useless food scale may actually come in handy here.

On to acidity. For all but one of the previous years' Seyval juice, the acidity was ideal or a bit low. So when I was picking up my juice, I also picked up some tartaric acid to bump up the acidity of my juice. Then I found out that the juice was actually way too acidic this year. I had to order something to reduce the acidity. Fallbright was sold out of many of the chemicals that are used to reduce acidity when I tried to order it, so I would assume that lots of people are having the same problem. I was able to order a bag of calcium carbonate (old-school chalk). The calcium carbonate does reduce the amount of acid, but it takes a couple months for the acid salts to precipitate out, so I definately want to get that started soon. Luckily the calcium carbonate came in the mail only 2 days after I ordered it!

I don't fully understand the relationship between pH and total acidity. My guess is that total acidity is a measure of the amount of basic chemicals that are needed to buffer the acidic juice. I think(?) different liquids have different buffering capacities, so adding the same amount of basic chemicals to two different liquids that have the same pH may not raise the pH by the same amount. Most of the calculations on the website are based off of the total acidity, so thats what I'll be focusing on as well.

The website suggests a finished total acidity (hearafter called TA) of 0.7 to 0.85. My juice is at 1.185. Some of the acid will go away during fermentation (0.12), plus if it is cold stabilized some of the acid will precipitate out (an additional 0.08). So the first thing to do is remove that from the total, leaving 0.985. I'll aim for a finished TA of 0.785, mostly just because the math is easier that way. So I'm aiming for a change of 0.20 in the TA level. According to the website, 2.5grams of calcium carbonate will reduce the TA by 0.1. I need twice that change, so I'll add 5g/gallon times 6gal, which comes out to 30grams of calcium carbonate.

The website also says that you don't want to go over a pH of 3.45 or the wine gets unstable and it gets easier for bacteria to grow. Since its already at 3.10, it can only change by 0.35. According to the website, approximately 0.35g/liter (1.323g/gal) will change the pH by 0.1. So that means that I shouldn't add more than 4.63g/gal. Now I don't remember chemistry all that well, but I seem to recall that the pH scale is logarithmic, which would make this whole calculation bogus. Nevertheless, I'll err on the side of caution and only add 4.5 g/gal. That would mean that the TA change would be 0.18, so the finished TA would be around 0.805. So the total calcium carbonate added will be 4.5 times 6gal or 27grams.

For the calcium carbonate, it strongly recomends taking 1/3 or less of the juice out, adding the calcium carbonate to that(slowly over an hour), letting it sit for a day or so, then siphoning it back into the rest of the juice, leaving any precipitate behind. "This helps to prevent excessive distortion of the entire natural acid profile." Whatever that means. Actually it says that ideally I should take out just enough to reduce the TA of the small batch to zero. OK, so 1.185 times 1 gallon times 25g (2.5g per 0.1) is 29.625 grams. Thats the amount that will neutralize one gallon. I'm putting in 27g, so I'll need just under one gallon.

So to summarize, I'm going to take out 1 gallon of juice, add 27grams of calcium carbonate, let it sit for 24 hours, siphon the juice back into the big batch, then add 3.7 lbs of corn sugar and stir till its dissolved. Sweet!