I learned of a different way to test for titratable acidity, the other day. At the last meeting of the Puget Sound Amatuer Wine and Beer Makers club, Don Proctor demonstrated this method using an odd looking device. He used ordinary baking soda (sodium bicarbonate) to neutralize the acid in a test sample. The important thing about this chemical reaction is that it gives off carbon dioxide (CO2) in direct proportion to the amount of acid neutralized. Now his device didn’t look so odd. The stoppers, tubing, glass cylinders, and green liquid were used to measure the amount of CO2, and if you know how much wine was in your sample and how much CO2 was produced, you can find the acidity of your sample.

The difference is in what you measure

This method, and conventional titration, both aim to measure the amount of acid by neutralizing it with a base. In a titration, you add a carefully measured amount of base until all the acid is neutralized. It’s important that you add just enough base to neutralize all the acid – no more and no less – because you determine the amount of acid in the sample from the amount of base that you add. Because you have to measure the base so precisely, it’s best to add it in liquid form. That means you need to have a solution of base at a precise concentration. Now, this is easy to find, but it’s expensive and it has a short shelf life.

Why the new way is better

You need to neutralize all the acid in Mr Proctor’s method too, but you don’t need to know how much base it took to do that. That means you don’t need to determine the end point (no pH meter) and you can use cheap, shelf stable baking soda instead of expensive perishable sodium hydroxide. That’s a big plus, as I found out the last time I ran out of chemicals. I’m going to have to get one of these contraptions!

Update 9/8/2008: A picture is worth a thousand words

If you’re having trouble visualizing it, take a look at this photo.

Higher yield from red wine?

I’m still surprised by the yield from my Merlot grapes. I bought 100 lb (45.45 kg) in October, and I was expecting about 5-gallons of wine, which is about what I’m getting from the 100 lb of Chardonnay grapes I bought at the same time. I think I know what happened. I treated the Merlot with pectic enzyme, then fermented it like any red wine, so the skin and pulp were soaking in a water-turning-to-alcohol mixture for a week. This, to say nothing the fermenting yeast, broke down cell walls and membranes making it a lot easier to squeeze liquid out of the pulp. The Chardonnay, on the other hand, were pressed immediately after crushing. The result: more Merlot wine from the same amount of grapes. I’ll have to make a note of this for next year to see if the extra yield from red wine is real or if this year’s experience was just a fluke.

The old and new measurements are all within 1 g/L. Since I’m measuring my liquid volumes with the plastic syringe that came with my cheap acid test kit, not pipettes or burettes, I don’t think I can claim accuracy better than 1 g/L. So I’m not going to say the new buffer is great, but any error its causing is pretty small.

You need to calibrate your pH meter for it to work properly, but to do that, you need to immerse it in a solution of known pH. Buffer solutions are the way out of that little chicken and egg problem. These are made of precisely measured ingredients that combine to form a solution of known, and highly stable, pH. It would be pretty tough for most home winemakers to make their own buffer solution, so it’s a good thing that they’re widely available at homebrew shops.

Not all buffers are created equal

I was out of pH 4 buffer, and bought some more from a local shop. The first difference I noticed, between the new and old solutions, was the color – the new one was pink and the old one was colorless. There were two other differences, though, that were more significant. Each solution came with a temperature table that indicated the precise pH, to two decimal places, at a given temperature. The old solution listed the pH from 0C to 95C in 5 degree increments, and over that wide range the pH varied from 4.00 to 4.22. The new solution listed the pH at 20C (pH = 4.02) and 30C (pH = 4.99). The detail and temperature stability of the old solution gave me a lot of confidence. The new one is … pink.

How to shop for buffer solution

My pH meter had been pretty steady, often needing no adjustment at all between uses. When it had drifted, it was only by 0.02 or 0.03. So I was taken aback to see my pH meter read 3.74 when I first put it in the new solution. Maybe the meter drifted by that much since the last time I used it, but maybe the pH of these two “pH 4″ buffers differed by 0.26. I was out of the old solution, so I couldn’t check this. The new solution is fresher, so it’s possible that the old one drifted over time, but I’ve got my doubts about the new one. Live and learn. The next time I buy buffer solution, and that’s going to be pretty soon, I’ll try to find out when it was made and how much detail is in the temperature table.

Once I pressed the Merlot, it was time to watch airlocks bubble as the wine fermented out and then slowly cleared. It was also time to clean the fermenter. This is on the list, along with washing bottles, of my least favorite things about making wine. The best way to do this is to get someone else to do it, maybe a friend or loved one. This isn’t as easy as you might think, so sometimes we must take drastic action. Yes, there are times when we have to do it ourselves.

If you gotta do it, do it the easy way

So how do you clean a 24 gallon fermenter? It’s big enough that bending over, or tipping it on it’s side and crawling in, to scrub the inside and bottom will be hard on your back and knees. Besides, why scrub when you don’t have to? I like to rinse it with a garden hose right after I’m done with it, that way nothing has a chance to dry and harden on the surface. Next, I fill it with water and a detergent, I like to use Oxiclean. You’re not going to want to move it while it’s full, so make sure it’s in a good spot before you fill it. You’ll want it someplace where you can leave it for a long time, someplace where you can tip it on its side, to drain, without getting it dirty, and someplace near a garden hose. The garage, just inside the door to the driveway, works for me. I like to let it soak for several hours, often overnight. After soaking, I’ll drain it and rinse with the garden hose. After I’ve rinsed thoroughly and I think I’ve gotten every bit of detergent, I’ll fill it with clean water and let it sit for a while (again, several hours or even overnight). I want to make sure there isn’t a thin film of detergent on the bottom or on the sides. I drain it after that and turn it upside down to drip dry over my utility sink.

Not as bad as it seemed

As you can see, this process can take several days, but for most of that time, the fermenter is just soaking. It takes very little time and effort on your part, leaving you free to make more wine!

When making red wine from grapes, you crush the grapes then ferment them. You leave the skins and pulp in the fermenting wine, for a time, then you press it and leave the solids behind. The amount of time will vary according to the style of wine you’re making. Three or four days, will yield a light bodied wine. A few weeks will yield a tannic, full bodied wine. A good full bodied wine requires top notch fruit, and since I don’t have detailed information on how my grapes were grown I decided to make a medium bodied wine, and pressed after a week.





Here you can see the bladder press I used to press my Merlot.

Using a bladder press

I loaded the fermenting wine, pulp skins and all, into a perforated cylinder. At first, “free run wine” flowed out of the perforations, leaving seeds, pulp and other debris behind. Later, I applied water pressure to inflate a rubber bladder that squeezed the grapes against the sides of the cylinder and “press wine” flowed out. Altogether, I got over eight gallons (30+ liters), which is more than I expected from my 100 lb (45+ kg) of grapes. I was going by the rule of thumb that 100 lb would yield 5 gallons (about 19 liters).





I kept the free run and press wine separate. The carboy on the left, with the orange handle, contains press wine, while the carboy on the right contains free run. It’s still fermenting, and I expect it to finish in another week. Once it starts to clear, I’ll rack into fresh containers for aging. At that point, I’ll have to decide if I want to keep the press and free run separate or combine them.