Maybe it’s the name that’s the problem. Good olive oil gets to be called ‘extra virgin,’ a sign not just of its quality, but that it should be treated with respect. Good sesame oil, on the other hand, has no such grading system; other than the words ‘refined’ or ‘toasted,’ you’re pretty much on your own when reading the label on a bottle of sesame oil and deciding whether or not to buy it.

But quality sesame oil matters. The good stuff is mind-expanding: an intense flavor, not just of sesame, but hints of other nuts; a delicate sweetness; and a rich viscosity that clings tight to the food it touches. Good sesame oil is just as important to your cooking as good olive oil or butter. So take a moment to be honest with yourself: How old is that half-empty bottle that’s sitting in your pantry, and is it any good?

Does sesame oil go bad?

The short answer: yes. Like olive oil, unrefined sesame oil is primarily composed of unsaturated fats that doctors say are good for us but, unfortunately, don’t last forever. The very moment a sesame seed is milled open, the clock starts ticking and the oils inside start to degrade as oxidation and hydrolysis break triglyceride fat molecules down into glycerol and free fatty acids. Phenols and other antioxidants naturally found in sesame oil slow this breakdown, and good storage can slow it even more, but the decay itself is inevitable.

Eventually, the oil will become rancid: it will turn darker in color, develop a harsh aroma like paint thinner or nail polish remover, and start to taste unpleasant. But there’s no tipping point at which the oil goes from ‘fresh’ to ‘rancid’—it’s a gradual process, and different for every oil.

Is rancid sesame oil safe to eat?

Unless something’s gone horribly, nightmarishly wrong, yes. Rancid does not equal spoiled or rotten; it simply means that oxygen has degraded the oil enough to change its taste and aroma. You’ve probably eaten rancid oils dozens of times and never noticed. However, since we mostly use unrefined sesame oil as a finishing ingredient at the end of cooking, freshness matters. If your sesame oil smells and tastes okay to you, eat it. If it doesn’t, chuck it.

How long does sesame oil last?

As much as we’d like to, we can’t give you a set lifespan for sesame oil. The best-by date on the package, using rules mandated by the FDA, is a start, but it’s honestly not that meaningful. The shelf life of a bottle of sesame oil has to take into account the initial quality of the sesame seeds before processing, how long the oil was stored after milling, the conditions of that storage, whether it was blended with other quality oils, the length of its trip in a shipping container on a barge, and the rate at which you use it at home. By the time you bring it home from the supermarket, most commodity sesame oil is already months or years old, and has substantially degraded from its original condition. Poor quality sesame oils are effectively dead on arrival—perfectly edible, but hardly the fragrant, toasty marvel that you’ve paid good money for.

Let’s put all that aside for a minute and assume you’ve bought some quality sesame oil and just need a ballpark figure. Once you’ve broken the seal, try to finish your sesame oil within six months. Store it in the fridge and you’ll get a few more months at peak condition, but don’t expect oil immortality. If you have an old bottle of unopened sesame oil, go ahead and give it a try, but it's best to open your bottle within six months of purchase.

What’s the best way to store sesame oil?

The most important part of storing sesame oil well is buying good sesame oil in the first place. Conscientious small batch producers will start with high quality sesame seeds and move their inventory quickly. Try this lightly toasted sesame oil from Queens Bucket, a producer in South Korea that specializes in low-temperature infrared roasting, which preserves more of the sesame seeds’ innate flavor. If you want a darker-tasting oil, we love Wadaman’s black sesame oil, which starts with intensely aromatic sesame seeds and has hints of roasted walnuts and cocoa nibs. The better the oil you start with, the better it’ll keep.

Another reason we love these bottles is because they’re petite; the smaller the bottle, the less air that can fit inside it once you start cooking with it, and the greater likelihood that you’ll finish it before the oil turns. Large tins of sesame oil may seem economical, but not if you wind up throwing a half-full one away because it’s become rancid.

Heat and light are just as bad for your oil as air, so keep your sesame oil in a cool, dark place, like a closed cabinet away from the stove or refrigerator. And never refill a bottle that contains old oil with new sesame oil; even trace amounts of older oil will rapidly break down the fresh stuff.

And most importantly, use your sesame oil early and often! This kung pao chicken recipe is a weeknight favorite of ours, and as you’re getting ready for grilling season, try these pineapple-grilled short ribs. Or make some spicy beef dumplings for a rainy day. Each of these recipes only uses a teaspoon or two of sesame oil, but when you have a small bottle of the good stuff, that’s all you need.

Get your hands on the good stuff

Queens Bucket Light Roasted Sesame Oil

Made using sesame seeds toasted by infrared rays at a much lower temperature than the mass market variety. This cooks the seeds through evenly without burning them, resulting the silkiest, nuttiest oil you will ever taste. Shop now.

Wadaman Black Sesame Oil

Don't let the light color fool you. This organic sesame oil is incredibly potent, with the dark cocoa nib and roasted nut flavors of Japanese black sesame seeds. Use as a finishing oil just like extra virgin olive, either on Japanese recipes or your favorite dessert. Shop now.

Wadaman Roasted Black Sesame Seeds

Best-quality roasted black sesame seeds from a Japanese roaster with 130 years of experience. Heady with nut and dark cocoa flavors and ready to sprinkle on seared tuna or your next bagel. Store in the freezer to keep fresh for as long as possible. Shop now.

Wadaman White Sesame Paste

A smooth tahini-like puree of organic white sesame seeds, also known as shirogoma in Japanese. Just a spoonful adds a light but luscious sesame flavor to Japanese recipes and desserts, and its lightness in comparison to black sesame paste is ideal for sweet fillings. Refrigerate after opening to keep it at peak flavor. Shop now.

Wadaman Black Sesame Paste

Made like the white paste, but with black sesame seeds; it’s also known as kurogoma in Japanese. Use a dollop to dress steamed edamame or make a killer batch of black sesame ice cream or panna cotta. Shop now.