Preserving Open Wine
Red wines tend to have more tannins than white wines because the grape skins are left in contact with the juice as it ferments, which imparts both tannin and pigments to the wine, both of which act as preservatives. Reds are often aged in oak barrels more frequently than whites, which imparts even more tannin to the wine.
How to Keep Open Wine Longer
You can extend the life of any opened wine by giving it a few squirts of liquid nitrogen, such as Wine Preserve, a spray sold in many liquor and wine accessory stores.
Another trick is to pour your remaining red wine into a clean, empty half bottle size and cork it. This also minimizes the amount of oxygen that can affect the wine.
Keeping your red wine in the fridge slows down the oxidation process. You’ll just need to take your wine out of the fridge for at least 20 minutes before serving.
These little tricks will help to extend the life of an opened bottle of red wine but most red wines start to slip after two days.