It's possible there could be some contamination causing the sourness, but if it looks turbid, there's likely a lot of yeast in suspension which can give a harsh bitter/sour flavor until it drops more clear. Also, using fruit tends to make beers drier and tart - it seems like you'd get fruity sweetness but the actual sugar ferments away. I say give it a week or two at those cold temps and sample. Once the beer is clearer you'll have a real idea what you have. Let us know.