Homebrewed hard cider turned sour after sitting for a few months

Question

I made two batches of hard cider back to back earlier in the year and they tasted great for the first two months after bottling. However, they turned into a sour mess around month three. Imagine dropping a warhead or two into your batch. It was a slightly disgusting taste. It definitely wasn't a normal, apple-y sour taste you'd expect. If this taste was much stronger I could almost compare it to an acidic vomit.

I'm trying to figure out WHY this happened so I can avoid it in the future. There was no visible signs of contamination. The cider itself smelled fine as well. The only problem was the strange, candy-like/fake (not sweet!) sourness.

My process was very simple on purpose. No chemicals or additives outside of BTF Iodophor to sanitize when needed. I wanted it as "organic" as possible. This stuff wasn't going to be around too long... I thought. Sugar water was added to the bottles themselves to get natural carbonation during bottling. I did add habanero peppers to one batch but they both had the sour issue anyways.

Process:

1. Apples bought from the store and juiced at home + .5 cups of sugar per gallon + yeast. This took about three days to ferment in the bucket.

2. Cider in bucket pumped to the carboy to sit for about a week to let tannins and bits of apple settle.

3. Cider in carboy pumped to the bottles sitting with a few teaspoons of sugar water in them.

4. Bottles sat for about a week to ferment and get the natural carbonation (which worked very well).

5. We enjoyed the cider from that point on to about two months later. However, it became obvious the cider (which had all been sitting in the fridge) was becoming sour like weak warheads.

Does anyone else know what happened or how I can prevent it in the future?

Answer 1

Sounds like you went organic alright. Which included a wild yeast on the apples or possibly an acetobacteria.

Using a big pitch of a aggressive yeast like Champaign yeast helps to insure it's the dominate yeast.

Wild yeast can consume sugars that brewing yeasts can't so one trick is to add sugar in hopes the dominate pitched yeast gets the cider above the ABV tollerance of the potential wild yeasts.

Campden tabs before or even after fermentation helps rid the must or cider of undesirable organisms too.

Some will even bring the must to a simmer or low boil for a few minutes to kill organisms, but this can drastically alter the must and flavor of the cider. So many true to the craft try to avoid it.