I made my first batch of wine this season. I made it from a grape vine in my yard. The grapes may be a cross between Isabella and Couderc Noir from what I have found out so far. At the first rack I could smell a slight smell. This smell was like what you would smell in a wet cave with old wine spilt on rotting wood. The smell got worse as time went by. The taste of the wine was ok. I tried to aerate the wine to get the smell out twice but it did not work. When the smell got so that you could detect it from about 4 feet away, with the air lock off, I them used Bocksin (30 mm for 5 gal). This produced a purple slime on the bottom of the carboy a little thicker than 1/4 inch. I racked it and now, after a month all of the smell is gone.
I want to understand what caused this to happen so I do not have it happen again.
We picked the grapes sorted out the spiders, steams and dried grapes. We then rinsed the grapes with cold soft water. I took a stainless steel potato masher to crush the grapes (about a 1/2 cup at a time) in a stainless steel pot and poured into the primary. All items used had been washed and rinsed with soft water, rinsed with RO water with Campton tablets dissolved in it. Then we rinsed with RO water. When the primary was filled (5 gallons) we put 5 crushed Campton tablets in, pectin, and yeast nutrient and stirred. The next day we put Lalvin D-47 into
2 cups of warm DI water with 2 table spoons of table sugar, after 2 hours poured it into the primary. The next day the yeast was going to town. I did not have anything long enough to stir the primary so I went out and got a long paint stirrer. I rinsed it with soft tap water then in RO water with Campton tablets dissolved in it, then with RO water and used it to stir the must. I would rinse it after each use and go through the above before each use.After a few days the foam and yeast activity seemed to be over, so I racked the wine using items cleaned as before. On the bottom of the primary I could smell the smell, but thought it was dead yeast smell. After racking the wine into a 5 gallon carboy the yeast became alive again. It was blowing off the top of the airlock and shooting purple foam out. By the next morning it had settled down a bit. After 30 days the wine was racked again. The smell was a little more evident so I poured it into the clean primary splashing then racked back into the carboy.
The next month when I racked the smell was so bad that you could be about 4 feet away and you could smell it. I poured into the primary again and splashed the wine aggressively and ordered the Bocksin. A week latter the Bocksin arrived and the smell was still there so I used it as how the bottle indicated to use it.
Any one out there have any ideas of what may of caused the smell and what I could do to prevent it in the future.
BTW: I used the same method and items to make a white wine and did not get the smell. There was only one difference, I dissolved the 5 Campton tablets and stirred the liquid into the primary after crushing the grapes.