How soon do coffee beans lose flavor

Question

I mostly brew my coffee using a cold brew method.

I store my beans in an air tight container. But it is a bit of a hassle to open the container.

Would the beans lose much flavor if they were exposed to the air?

I use up the beans within 2 months.

Answer 1

There are a number of considerations, including:

• What happens in absolute terms.
• What happens relative to your own sense of taste and smell.
• The nature and usage of the air tight container.

Flavor loss

Two actions are the big contributors to coffee losing its flavor: loss of aromatics through evaporation and oxidation. These happen quickly on the surface and take longer in the interior of the beans or grinds. The finer the grind, the faster it loses flavor, both because there's more surface area and the interior is closer to the surface.

So coarse grind for cold brew will take longer to noticeably deteriorate than medium grind for drip coffee makers, and whole beans will take longer than coarse grind. Grinding the beans shortly before you're ready to use them will preserve the most flavor and minimize off-tastes from oxidation.

Personal differences in taste and smell

So that's what happens to the coffee, but different people are more or less sensitive to it. Connoisseurs may taste the difference in ground coffee that's been exposed to air for a number of hours. People with cast iron palates who drink utility coffee may not notice the degradation until the coffee is very old. People also start to lose some of their sense of taste and smell as they get older, and may be less sensitive to the difference in taste of old coffee. So it isn't so much a question of how much the flavor has degraded in ways you would measure in a lab, its how much degradation does it take for you to notice it.

If you're serving coffee to guests and you're a connoisseur and they're utility coffee drinkers, the nuances that give you great pleasure may be totally lost on them. If you're the one with a cast iron palate and your guests can appreciate good coffee, old coffee that tastes fine to you may leave your guests wondering how you get it down.

Air tight containers

Storing the coffee in an air tight container may slow the degradation, but not all air tight containers or methods of using them will do so. If the coffee is sealed in a close-fitting or vacuum evacuated, air tight container that stays sealed, it can last for a reasonably long time. But if the container contains a lot of air space, and/or you regularly open it to dispense coffee, the fact that the container may be air tight doesn't buy you much.

If the container is a pouch with a one-way valve so you can squeeze out the air when you reseal it, it will last longer than a can or canister with a tight-fitting lid. Every time you open the container, some of the aromatics escape, and you introduce air. With a can or canister, that fresh air oxidizes the coffee during storage after you reseal the container. If you have a vacuum canister that gets pumped out by a vacuum sealer, you minimize the oxidation but still lose some aromatics.

Storage time recommendations

The storage times recommended by coffee packagers varies by the market audience for the coffee. Specialty coffees whose market is discriminating drinkers are likely to carry a "best-by" date of around 6 months for the sealed package. On mass-market coffee, that's typically pushed to more like a year. But those recomendations are for the still-sealed container. Once you open it, the shelf life is much shorter. When you first open year-old coffee, you'll get the aroma that was trapped in the container, but the flavor will quickly degrade. Ground coffee will taste stale to many people within a few days.

So how long you can keep coffee without it losing flavor depends on how fresh it is. Freshly roasted coffee needs to age a little if you get it directly from a roaster, but otherwise, the fresher it is, the longer it will last. Start by buying coffee as close as possible to when it was roasted. You can contact the coffee company and ask how many months the use-by date on the package is from the roasting date. For the longest shelf life, try to buy coffee as much under 6 months old as possible.

For relatively fresh whole beans stored in a vacuum canister after opening the retail package, I've seen recommendations that the average coffee drinker can taste the difference after 6-8 weeks. Other recommendations say many people can taste the difference after 2-3 weeks. If you leave the beans in a retail pouch with a one-way valve and keep the air squeezed out, I've seen recommendations of 2-3 weeks shelf life before the average coffee drinker will notice the difference. For a non-air-tight container, the recommendations are even shorter. And all of those time frames are shorter for ground coffee.

How do the recommendations apply to you?

But if it is just you drinking it, go by what you can taste. My wife opens a year-old, giant canister of mass-market ground coffee, and spends many months working her way through it. By the time the canister is half full, the only aroma is of very stale coffee. By the time she gets to the bottom of the canister, it smells like medicine. But it tastes fine to her.