It was literally rotten like it didn’t just smell and taste off it was rotten like the peaches went bad during the whole process
Hm... you could look at your process. Here's what I do:
1. Choose fully ripe peaches, discard any overripe or spoiled ones. Remove the stones, but leave the skin. Cut off any bad spots. Freeze until ready to proceed.
2. Thaw peaches. While they are thawing, add pectic enzyme to help break down the fruit pulp.
3. As soon as they are mostly thawed, put in primary fermenter, add water and sugar, add Kmeta (or a Campden tablet) to kill natural yeast and bacteria.
4. Wait 12-24 hours, then check the pH and add acid blend as needed. I also add a little bit of powdered wine tannin as "sacrificial tannin" (look it up).
What keeps them from spoiling?
* Start with ripe peaches in good condition.
* Add Kmeta as soon as they are mostly thawed (that will kill natural yeast and bacteria, and help prevent oxidation). If you don't freeze them, add the kmeta as soon as they are cut up and in the fermentation bucket.
* Adjust the pH to around 3.4 (that will kill many micro-organisms)
* Added tannin is an anti-oxidant and will help to preserve fruit flavor
Taste at every stage along the way. It should always taste good, not spoiled. During fermentation, I taste a few drops every day to help me monitor progress. If it starts to taste rotten, at what stage does that happen?
Yes we added yeast and nutrients. Half a pack of yeast and 1tbsp 2 days after yeast and then another 1 tbsp 2-3 days after the first time.
What size what your batch? If you add too much wine nutrient, it can give it a bad flavor. It also provides nutrients for spoilage organisms. So you want enough, but not too much. When I first started, I used "Yeast Nutrient," but I have switched Fermaid-O and Fermaid-K. When I was using Yeast Nutrient, I think I used 1-2 tsp. per gallon, so if you were doing a 1 gallon batch you might have used way too much nutrient.