Answer:
The factor is called a "catalyst." The wine sours more slowly when stored in closed bottles because there's no "oxygen" inside the bottle that could lead to an increase rate of decomposition.
Step-by-step explanation:
Wines are naturally stored with a cork. The cork prevents oxygen from entering into the bottle. As you probably know, wines have natural bacteria which play a role in the process of fermentation. Once bacteria are introduced to oxygen, they multiply. However, in the process of fermentation, there's no oxygen present. So, once the bottle of wine is opened, it should be consumed immediately because exposing it to air will change its flavors.
A "catalyst" is a factor that affects reaction rates. Their presence hastens the time for decomposition.