because it gets oxidised when it gets contact with air.
It's called oxidation. The acids will give up electrons (take in oxygen) and turn from bitter to sour.
sour wine, or vinegar, is called 'du vinaigre' in French.
Vinegar (vin aigre = sour wine)
Vinegar can be produced from wine.
vinegar is just sour wine. lol
VINEGAR
The most ideal place would be a cellar that does not get much sunlight. That is wine needs a cool place to ferment and if there is sunlight it can make the wine go sour.
vin acide
The sour liquid produced by the fermentation of wine is called vinegar. It is created when acetic acid bacteria convert the ethanol in wine into acetic acid. Vinegar is commonly used in cooking and as a condiment.
air is not good for any wine it makes it sour so froth or bubbles are not really wanted anyway.
The milk gets infected with bacteria present in the environment, some of which produce acids and other compounds as a byproduct of their digestive process when they consume compounds present in the milk. That's what gives it the sour taste and sometimes rank smell. If you inoculate it with the right strain of bacteria, lactobacillus acidophilus being one, you get yogurt. L. acidophilus consumes lactose, a sugar in the milk, and produces lactic acid that gives yogurt its tangy flavour.
Try red currant jelly melted in