Have you bought some oyster sauce for a recipe but never got around to using it? If so, you’re probably wondering:
Has my oyster sauce gone bad? How long does it last?
Don’t worry. We will answer all of your questions below.
For those who want the answers now: In summary, unopened oyster sauce will generally last 3-6 months past the best-by date. As soon as you open the oyster sauce, it can stay fresh for 3-6 months for its optimal quality.
How To Tell If Oyster Sauce Has Gone Bad

Some tell-tale signs that your oyster sauce has gone bad are the presence of white or green fuzz on the surface or an off-smell. If you find this in your oyster sauce, discard it.
Over time, the sauce will darken, and its flavor will become stronger. If it’s too strong for you, you may want to throw it out as you’re unable to enjoy it in your dishes.
Oyster sauce is naturally thick, thanks to the presence of cornstarch. If you notice that water starts to separate on the surface, it’s a sign that the condiment is old. If your oyster sauce does this, it’s best to get rid of it.
How To Store Oyster Sauce

Unopened oyster sauce should be stored in a cool and dark place, like the pantry. Once the sauce is opened, the question is: do you refrigerate it?
Yes, the answer is affirmative!
The cold temperature helps to preserve the sauce for longer. It won’t go bad if you leave it at room temperature, but the quality will degrade faster.
For that reason, store the oyster sauce in the fridge if you’d like it to last longer, but if you know you’re going to use a whole bottle up within a month, you should be fine keeping it on the counter.
How Long Does Oyster Sauce Last?

Generally, oyster sauce has a shelf-life of about 18-24 months. Check the best-by date on the label to determine how long yours will keep for. Of course, the sauce can still last a couple of months after the best-by date.
If unopened, oyster sauce can last 3-6 months past the best-by date.
As soon as the sauce is opened, it will last 3-6 months in the fridge. If you’ve bought one of the more high-quality oyster sauces, it should retain quality even longer, like up to a year.
Substitutes For Oyster Sauce

Firstly, soy sauce can be used as an alternative to oyster sauce. Because it lacks the syrupy consistency and the sweetness of oyster sauce, use less soy sauce with a pinch of brown sugar.
Or you can try sweet soy sauce to add to your dish instead of oyster sauce.
One of the best substitutes for oyster sauce is hoisin sauce. You can use it in equal quantities to the amount of oyster sauce you would have used. Alternatively, use soy and hoisin sauce in a 1:1 ratio.
The Bottom Line On Oyster Sauce
Oyster sauce is made from caramelized oyster juice, salt, sugar, and sometimes soy sauce thickened with cornstarch. This brings a dark, syrupy sauce that is the signature of the condiment.
Oyster sauce can last a relatively long time. But if you’d like to keep it fresh for longer, store it in the fridge. Oyster sauce can last 3-6 months in the fridge after it’s been opened.