I’ve never been happier with a specific gravity measurement than this one: 0.993 on 8/31/07. After the pH crash and the stuck fermentation, after the potassium bicarbonate addition and the yeast starter, and after all that waiting my Oregano Wine has finally fermented out! I racked on 9/3/07 to a 1-gallon jug and a half-bottle. I poured the thick slurry that was left into a beer bottle to settle. I’m a little worried about oxidation because I’ve kept the wine in it’s primary fermenter since June, but there is no sign yet and I’ve treated with sulfite.
I’ve been stirring my oregano wine every day since I used potassium bicarbonate to raise the pH. Yesterday I took some measurements, and I found some good news and some bad news. The good news is that I succeeded in raising the pH to 3.67, and that’s high enough to permit fermentation. The bad news is that it hasn’t actually started fermenting again. It’s a waiting game for now, but if I don’t see activity in the next few days I’ll add more yeast.
I tested a sample of my oregano wine yesterday. The specific gravity is 1.053 and the pH is 2.62. These results are virtually unchanged from 7/13/07 when I first noticed the pH crash that stopped the yeast in their tracks. I’ll try to get them going again by neutralizing some of the acid, raising the pH, with potassium bicarbonate (KHCO3). I had planned on adding two teaspoons because I wanted to add about 10 grams, and I believed that one teaspoon was 4.8 grams. The vendor, Crosby & Baker, says that 1 teaspoon is about 6 grams and warns against using more than 10-13 grams per gallon. That would put two teaspoons, at about 12 grams, very close to the upper limit, and since measuring spoons are not precise I decided to only add one teaspoon this time. I’ll see if fermentation restarts and I’ll retest the pH.
I’ve also decided to add one teaspoon of cream of tartar. The reaction of KHCO3 with tartaric acid will create cream of tartar. By adding some more, I’m seeding the wine and that will encourage the newly created stuff to precipitate out more easily. I’m also hoping it will improve the buffering capacity of the wine.
I’ve been thinking about the pH drop that brought fermentation to a near halt, and I’ve decided to deacidify with potassium bicarbonate (KHCO3). Most of the information I could find on neutralizing acid has to do with reducing the total acidity (TA); I couldn’t find anything about deliberately raising the pH. That means I have no clear guide in deciding how much KHCO3 to add. When I last measured the TA, it was 6 g/L. I’ve arbitrarily decided to neutralize half of it. To reduce the acidity by 1 g/L, you need to add 0.9 g/L of KHCO3. Since I’ve got a gallon (3.785 L) of wine and I want to neutralize 3 g/L of acidity, I need to add 10.2 g KHCO3 (0.9 * 3.785 * 3). I haven’t got a scale accurate enough to measure out 10.2 grams of anything, but a teaspoon of KHCO3 is about 4.8 g so adding two teaspoons (about 9.6 g) gets me pretty darn close to 10.2 g.
So what happens when I add the KHCO3? It combines with the tartaric acid to form potassium bitartrate (cream of tartar), carbon dioxide, and water. The cream of tartar precipitates out and the CO2 bubbles off leaving a tiny bit of water. That should leave the wine with a high enough pH to kick start the fermentation. I’ve ordered the KHCO3, it will arrive in a few days, and then we’ll see if there’s method to my madness.
Most of the info on neutralizing acid came from Philip Jackisch’s Modern Winemaking. It’s a good book that provides technical detail on winemaking processes with examples. It’s for the winemaker looking to go beyond the basics, and I highly recommend it. There’s even has a chapter on non-grape wines!
My oregano wine has been fermenting very slowly, and I suspected a pH problem. I was following a recipe that called for 3 tsp of acid blend. I decided to add only 1 tsp at the beginning, because I was afraid the pH could drop so low that it would inhibit the yeast. The must was mainly sugar and water, so there wasn’t much to buffer it – a little acid could push the pH a long way. Yeast has a difficult time when the pH drops below 3. I decided to take a sample and do some measurements. The pH meter, reading 2.69, confirmed my suspicion. The specific gravity was 1.052, which is less than the 1.060 on 6/30/07. That means it’s still fermenting, but it’s been over a month and it’s still got a long way to go. I measured the TA as 6 g/L (tartaric). I’m not sure what to do about this yet. I might be able to rack it and let it ferment out slowly under an airlock. I could try and neutralize some of the acid, pushing up the pH, to get fermentation going again.
Update 7/25/2007 – Fixing the pH crash by neutralizing acid
To fix the pH crash, I neutralized some of the acid with potassium bicarbonate (KHCO3). This will raise the pH and should get things going again
Here’s a photo of the oregano wine I started the other day. It was quite frothy just after I stirred it, but the bubbles subsided before I could capture the image. I stir for two reasons: During the first day, I want to incorporate oxygen into the fermenting wine to help the yeast grow. Later, I stir to keep the yeast in suspension. If I didn’t do this, the yeast might settle near the bottom, quickly consume the nearby sugar, then start to go dormant.
And you thought tomato wine sounded strange! Years ago I started an oregano bush from seed. Each year I harvest a little for cooking, but it’s huge and most of it goes to waste. What’s a winemaker to do? Use this recipe from Terry Garey’s Joy of Home Wine Making, my first winemaking book. It’s a great way to start – it’s how I got started – making your own wine.
4-6 cups (1-1.5 liters), packed lightly, of fresh herbs
1 gallon (3.785 liters) water
3 lb (1.4 kg) sugar or 3.5 lb (1.6 kg) honey
1 tsp (5 grams) yeast nutrient
0.125 tsp (0.3 grams) tannin
3 tsp (15 grams) acid blend
sulfite to 50 ppm (equivalent to 1 campden tablet)
Initially, you will need a fermenter, hydrometer, thermometer, stirring spoon, measuring spoons, and a couple of pots. Later, we’ll use a gallon jug, a racking cane, some siphon hose, and pH papers.
Start by sanitizing the clean equipment by immersion in boiling water or sanitizing solution. Harvest about 6 cups (about 1.5 liters), lightly packed, of oregano. Then remove dead leaves and any other plants that have gotten mixed in. After a quick rinse in cold water, place the oregano in a 2 quart (2 liter) saucepan, add 1 quart (1 liter) water, and bring to a simmer. As soon as it started simmering, take it off the heat and let sit for 1-2 hours. In the meantime, I dissolve the sugar in boiling water.
Strain the oregano and add the sugar water. Next, I dissolve the tannin and nutrient in water and add to the fermenter. Wait until fermentation is complete before adding the acid because the pH could drop too much during fermentation and inhibit the yeast. Finally, I add 1 tsp of sulfite solution (equivalent to 1 campden tablet).
Always take a hydrometer reading before pitching the yeast. I recorded a specific gravity of 1.108 @ 82 Fahrenheit (about 28 Celsius) when I made this recipe. My hydrometer is calibrated to work at 60F (15.5C), and I adjusted for the higher temperature with a lookup table. The adjusted SG was 1.110, so the potential alcohol was 15%. I thought it might turn out to be high, but I like to follow recipes closely the first time. I’ll probably cut the sugar and aim for and SG of 1.090 (12% alcohol) the next time.
At this point, turn if over to the yeast. Once fermentation subsides, rack the wine to an airlocked glass jug. When fermentation is complete (check with a hydrometer), add the acid.