Effects of Humidity on stored coffee
Keeping coffee beans and grounds fresh is imperative to the overall flavor yielded by the desired brewer, meaning that fresh coffee is usually the best. One of the biggest threats to all kinds of coffee is humidity.
When it comes to green coffee beans, too little humidity will cause the beans to dry out too much, but too much humidity will cause mold growth.
Storing green coffee beans is a little more tricky when compared to roasted whole bean and ground coffee. This is primarily because green coffee beans are great at absorbing excess moisture in the air, which can lead to disastrous consequences.
For the most part, when buying green beans, they will come in packaging that is suitable for long term storage. But, once the package is opened, the leftover beans must be stored properly.
In the packaging, green beans can last upwards of a year, but once opened, Green beans are best stored in an airtight container in an environment between 50-55% humidity, and at around 50 degrees Fahrenheit, or 13 degrees Centigrade. This is to help ensure that the coffee beans maintain a humidity level as close to 12% as possible. If at any point the green beans become wet, it’s recommend to roast them as soon as possible, as while drying, mold may start to grow.
Humidity also has an impact on coffee that has already been roasted, especially ground coffee.
Whole beans are easier to care for once their one way package has been opened, as they have less surface area than ground coffee does, meaning it doesn’t go stale as quick. Much like green beans, roasted beans and ground coffee should be stored in an airtight container and kept in a cool and dark place.
As perfect as it may seem, the last place you want to store your coffee is in the fridge or freezer. This is because each time you pull the canister out of the fridge and open the lid, moisture will rush into it, effectively saturating the coffee. Opening the canister while cold can also cause condensation to build up inside, which can cause mold as well.
Keeping pre-ground coffee fresh is likely the most difficult, but keeping it in an airtight container, and in a similar environment that whole beans stay fresh in, the ground coffee should last into the week without any adverse flavors forming.