As an expert sommelier and brewer, I can confidently say that it is generally safe to drink a bottle of wine that has been left open overnight. While it is always recommended to re-cork the bottle and place it in the fridge to preserve its freshness, there are circumstances where you might forget to do so or even discard the cork. In such cases, you can still enjoy a glass of wine without worrying too much.
When a bottle of wine is left open, it is exposed to oxygen, which can start to deteriorate its quality. Oxygen reacts with the compounds in wine, causing oxidation, which can lead to changes in taste, aroma, and overall character. However, the extent of this oxidation depends on various factors such as the type of wine, its age, and the amount of time it has been exposed to air.
In my personal experience, I have found that younger wines tend to hold up better when left open overnight compared to older, more delicate wines. This is because younger wines generally have more robust flavors and tannins that can withstand a bit of oxidation. On the other hand, older wines, especially those with subtle nuances and delicate aromas, can be more adversely affected by exposure to air.
If you find yourself with an open bottle of wine that has been left out overnight, there are a few things you can do to mitigate the effects of oxidation. Firstly, give the wine a quick taste and evaluate its quality. If it still tastes pleasant and enjoyable, then there's no reason not to pour yourself a glass. However, if you notice that the wine has taken on a flat or vinegary taste, it may be best to discard it.
Additionally, you can try decanting the wine before serving. By pouring the wine into a decanter or even a large glass jug, you can help reintroduce some oxygen and potentially revive the flavors. Swirling the wine in the decanter can also help aerate it further, allowing any lingering off-notes to dissipate.
It's worth noting that not all wines are created equal, and some varieties are more resilient to oxidation than others. For example, robust red wines like Cabernet Sauvignon or Syrah tend to fare better than delicate white wines like Riesling or Sauvignon Blanc when exposed to air. This is due to the higher tannin and acidity levels in red wines, which act as natural preservatives.
While it is generally recommended to re-cork and refrigerate an open bottle of wine, drinking a bottle that has been left open overnight is usually safe. The extent of oxidation and its impact on the wine's quality will vary depending on factors such as the type of wine, its age, and the duration of exposure to air. Trust your palate and give the wine a taste before deciding whether to enjoy it or discard it.