Rutabaga Soup Fermented? (Contained apple sauce)

[Franklen]

Made a rutabaga bisque and boy that was a big pot of soup from a bowling ball sized 'baga. Whole pot of soup was stored on our kitchen steps shelving (unheated area, but warms up some from sunlight). However, I continued to eat the soup for a week or so afterwards, then forgot about it for a few days. At about the two wek point I brought it into the kitchen, transferred to a smaller pot, and stored in the fridge. A few days later I decided to freeze what was left.

I opened the pot, the soup looked fine, no mold or anything present, tasted it and it seemed like it had a bit of a vinegary flavor to it. I thought nothing of it, packaged it up in canning jars and froze in our freezer. But as I was doing so a housemate tasted it and said it was no good, another housemate tested it and said it has just fermented (but she wouldn't eat it).

It had applesauce as an ingredient (almost a whole quart jar's worth), and so the thought is that is the fermenting ingredient here. But the question is, is the whole soup still okay to eat? I'm thinking due to the vinegary taste that eating it as soup might not be so yummy anymore, but it could be used in baked goods perhaps?

Thanks for reading my first post here!