The coffee you buy at the store isn’t fresh.
Usually, the coffee sitting on the shelves at the grocery store is months or even years old.
You might be used to drinking this coffee. Most people are. Coffee beans that are too old have gone stale, and when you brew coffee with those beans, you’re missing out on flavor.
Coffee beans are at their best between 2-10 days after they have been roasted, although they can typically keep their fresh flavor for about a month.
What causes this?
When coffee is roasted, the beans are being cooked, which means CO2 is being released, and a lot of it is trapped inside. If there is a lot of CO2 in the beans when you brew them, it ruins the taste. After roasting beans, it takes time for them to degas. Roughly 40% of the CO2 is released within the first day.
Letting the beans degas for a couple days before brewing them is optimal. You’ll even notice bubbles forming when the ground beans are soaked in water to be brewed. This is the excess CO2 being released, even several days after roasting.
There is an upper limit to beans, too. They can become stale after too long.
Exposure to oxygen will cause your beans to become stale. Storing your beans in a sealed jar and in a cool, dry place will help keep them fresh longer.
This is also why you should never buy pre-ground beans. The oxidation process is affected by the amount of exposed surface area; because ground beans have more of their surface area exposed, oxygen affects them quicker. Grinding up your beans can cause them to lose their freshness within hours, so always brew soon after grinding and never buy pre-ground.
How can you buy good beans from the store?
If you walk down the coffee aisle at the grocery store, you’ll see many brands, some mainstream, like Starbucks or Dunkin, and others more local. If you want the freshest coffee, look for bags that show the roast date. If there is no roast date, you can guarantee those beans are stale. Ideally, you want to buy beans less than a week old.