Why You Should Never Try To Regrind Already-Ground Coffee
In the bleary-eyed hours of the morning, every action before a cup of coffee may seem blurred. Say the beans are thrown into the grinder, and a setting that's too coarse is hastily selected. Or even worse, the bag snagged last minute at the store was ground for cold brew, rather than the espresso machine on hand.
When a batch of ground beans is too coarse, it may seem logical to simply regrind for the desired application. However, coffee grinders are not actually designed for such an operation – The grounds will turn into a thick, sticky paste that will infiltrate every crevasse of the grinder. Additionally, the result won't be suitable for a brew of any kind since the texture will be completely off.
To add to the disappointing result, regrinding the coffee will also worsen the taste. Exposure to oxygen lessens a brew's flavor, and a regrind is an overabundance of oxidation in one go. So instead, stick to using the grounds for their designated brewing method, or repurpose them as fertilizer. Let's explore more reasons to always grind fresh.
Freshly ground coffee brings out the best of a brewing method
Foremost, it's necessary to understand how grind size is intertwined with the brewing application, By the nature of the extraction method, espresso necessitates a much finer coffee size. The grounds need as much surface area as possible since water is quickly sent through them at high pressure. Conversely, for a method like cold brew — where the coffee seeps — the grind size is substantially larger. Grind size also affects taste — the coarser it is, the more acidic the result (per Matter).
In a perfect world, the best way to prepare a morning cup is by grinding the beans right before preparation. Buying pre-ground beans and drinking them within a few days is also doable, as such a course of action minimizes the coffee's loss of flavor, which happens quickly.
Once a bag of coffee is opened, even whole beans will go stale in about a month. Grind the joe, and the freshness gets cut even more — down to only a week. While an expired bag of coffee won't cause illness, it will lack any palatable flavors, per Beanground. However, the caffeine levels won't be affected, so it's fine to gulp it down in a pinch. As a result, try to keep your whole beans sealed and double-check the grind size to avoid any waste.