Wine that is turning sour is not Kosher for Kiddush.
Even if it's not yet vinegar - and it still deserves the Bracha of Hagefen - but it smells sour, then it cannot be used for Kiddush.
Kiddush wine should not be left uncovered for long periods of time.
Wine that isn't clear should preferably be strained before Shabbat before being used for Kiddush. If it has a white "skin" on it then it cannot be used for Kiddush as it's probably going sour.
One may use grape juice for Kiddush.
Source: Kitzur Shulchan Aruch 77:5
- Danny Erev Shabbat Eikev, 21 Av 5768
Please daven for ESTHER DEVORA bat MINDEL RUTH - אסתר דבורה בת מינדל רות