Question

Gracie squeezed some grapes and kept the juice in a vessel for 5 days at room temperature. On the fifth day she found that the juice tasted sour and appeared frothy.

Answer 1

The juice is most likely infected with yeast (which floats around in our atmosphere) which start to ferment the fruit. The product would obviously be ethanol and a lot of additional products like acetic acid and lactic acid which increase pH

Answer 2

thank you! :)