Cup of joe taste a little more bitter than usual this week? It’s quite possible you’re sipping on stale coffee. Contrary to popular belief, how long ago you bought your coffee beans isn’t the only determinant of how fresh they really are.

Indeed, there are several ways to tell if your beans are fresh or passed their prime that actually might be more effective than checking their expiration date. To help you enjoy deliciously fresh coffee from the comfort of your home daily, we spoke with a coffee expert to learn exactly how to tell if your coffee beans have gone stale, plus how to prevent it from happening so quickly.

How can you tell if your coffee beans are stale

According to Genevieve Kappler, Roasting Plant Coffee’s roast master, beans are susceptible to spoilage just lke any other food. “People don’t typically think of coffee beans as a food that can go bad, but coffee drinkers should learn to treat their coffee beans like produce or baked goods, which are highly perishable and so much tastier when fresh,” Kappler says.

This means that how long it’s been since you bought your coffee beans is just one factor that comes into play when determining how fresh they are. To conduct a more well-rounded and accurate analysis than simply checking the use-buy date on your coffee’s packaging, Kappler recommends basing your judgment on a few sensory cues (including the look, taste, and smell) instead of just the use-by date to determine whether or not your beans are good to consume.

For starters, Kappler says to analyze how the coffee reacts with water upon contact. “Look for the crema or bloom of foam when brewing espresso, pour-over, or French press,” she says. “This is a visual cue that the beans are still at their prime.” In tandem with how the coffee looks, Kappler also notes how it tastes and smells. “If you taste full flavor and smell the wonderful aroma of a smooth cup with no bitterness, that means you’ve got a cup of freshly-roasted coffee,” she says. On the flip side, coffee with a flat, bitter flavor or weak aroma are telltale signs of stale coffee.

So, what exactly makes these precious beans go bad? “Time and oxygen have the biggest impact. Scientific studies explain that roasted coffee is inherently volatile and quickly degrades regardless of how it’s stored, losing up to 70 percent of its flavor and aroma in a week or two. After that, exposure to oxygen turns the natural oils rancid and bitter,” Kappler says.

The best way to store coffee to prevent it from premature spoilage

According to Kappler, heat, light, moisture, and air (i.e. the oxygen mentioned above) are the key elements that will lead to the premature demise of your fresh coffee beans.

To protect your delicate beans from these conditions, it’s best to store them in an airtight container in a cool place for optimal freshness (like a cupboard) and use a container of the appropriate size. “The size of your container in relation to the volume of coffee is also important. You should try to leave as little space as possible for oxygen, so the coffee is protected from oxidation,” Kappler says.

Once you have your beans in an appropriately-sized container, they can be stowed away in a cool place in your home—but don’t let them get too cold. “Coffee should not be stored in the refrigerator or freezer, as it will absorb all the smells and moisture plus risk being exposed to condensation,” Kappler says.

Coffee bags with valves can also help keep beans fresher. “High amounts of carbon dioxide are released after roasting, and the one-way valve prevents a sealed bag from bursting. It also stops oxygen from getting into the bag, as oxidation turns the natural oils rancid and bitter,” Kappler says.

Keep in mind, however, that despite how you store coffee, it will continue to diminish in quality regardless—just not as quickly as it would if fully exposed to the elements. “It’s important to note that even in the absence of oxygen and moisture, roasted coffee will lose its freshness over time, as it is intrinsically an unstable product,” Kappler says. And, unfortunately, once the coffee has gone rancid, there’s no turning back. “Think of it this way: Can you revive a rotten tomato or a carton of rotten eggs?”

TL; DR? For peak quality, brew your coffee beans within a week or two for optimal freshness.

Other steps to take to make the freshest coffee at home

1. Buy freshly-roasted beans

For starters, Kappler recommends using freshly-roasted beans whenever possible. “Make sure you’re buying beans that were freshly roasted. Roasting Plant Coffee is the only coffee chain to roast in every café so that every cup is full-flavored, smooth, and never bitter,” she says. “If you’re curious when the coffee at your local coffee shop was roasted, just ask! If they don’t know the answer, chances are it’s probably stale.”

2. Avoid grinding them until you’re about to brew

Another important way you can help prolong your beans’ freshness is by keeping them whole. “Whole beans trap the carbon dioxide and aromas inside. The moment you grind, you create millions of pathways for the trapped gasses and aromas to escape, staling in a matter of hours,” Kappler says.

This also correlates to how finely-ground the coffee is. According to Kappler, “The finer the ground, like an espresso ground, the faster you’ll lose all the aromas, which is why espresso should always be prepared by grinding just before being extracted.”

3. Use a burr grinder

Kappler recommends keeping a burr grinder handy at all times. “I like a Baratza or a TIMEMORE hand grinder. Having a good grinder allows you to grind easily right before you brew, and burr grinders help ensure that your beans will be in their freshest, most consistently-ground, not-heated-up state for as long as possible.”

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