In these trying times, it’s hard to imagine there could ever be leftover wine at the end of the night. But if you’re exercising restraint and having a glass of wine at dinner and not a bottle (well done), the remaining juice doesn’t have to become another dusty cooking wine.

According to online wine subscription service Good Pair Days, it’s important to understand what ‘bad’ means in the first place. This description can range from the ‘vinegar-isation’ of wine, which takes place over a long period of time, to the more common, flattening or deadening of a wine’s flavours and aromas after coming into contact with oxygen. The latter is more likely what’s happening to last night’s half-empty bottle of shiraz on the counter.

“When we open a bottle of wine, we allow air to fill the space between the remaining wine and the cork or stopper, and that air breaks down the acids and tannins, and cause it to lose its structure,” says Good Pair Days founder and sommelier, Banjo Harris Plane. “It’s the same process which helps wine age and ‘breathe’ when we swirl it around our glass, but extreme levels of oxidation can cause wine to be unpalatable.”

Harris Plane, a former sommelier at Melbourne’s Attica, says wines with a high level of tannin and acid (think full-bodied wines like cabernet sauvignon, for example) can handle more oxidation before they become “too flat and flabby” to drink. Lighter, gentler wines, such as pinot noir or sparking, on the other hand, will break down much more quickly and are best drank sooner rather than later.

What you need to consider, first and foremost, is storage. If you don’t intend on finishing the bottle, it needs to be kept away from oxygen, heat and light. For red wines, that means sealing the bottle with a cork or wine-stopper and leaving it in a cool, dark place. “Full-bodied red wines will probably taste even better for a day or two after opening,” says Harris Plane. “But three to five days is the general rule for most wines.”

White wines and rosés, meanwhile, should be corked and kept in the fridge for a similar time frame of three to five days. “These wines are still palatable and tasty for up to a week, although most people would agree that five days is really the longest you should store them once opened.”

It’s not that the wines will be dangerous to drink, but leaving it any longer will kill off a wine’s more interesting features and subtleties. “All of those lovely fruit flavours will be the first to die off, leaving behind something quite different from the winemaker’s intended character (and usually, a fairly harsh set of characteristics),” he says.

Folks at home should also get used to tasting any leftover wine before sending it to the sink or back of the cupboard. Look at the colour of the wine, smell it. This will help you understand how wines can change and develop over time, whether it’s for the good, the bad or the ugly. “Oxidised white wines turn muddy and amber in colour, and red wines go a murky brown,” says Harris Plane. “Oxidation in small quantities rounds out harsh edges, but too much oxygen and the aroma will stink of cider vinegar, and the wine will be as flat as a pancake.”

Good Pair Days is now hosting free virtual wine gatherings on everything from how to store wine, to tasting wine like a pro. See more at goodpairdays.com