We’re all over-shopping a little bit these days. If you’re stockpiling coffee, you might be wondering how to keep it fresh for as long as possible. This week we’re going to talk storage and get into the details of how coffee ages, how to slow that process down, and how you can store coffee at home to optimize freshness and flavor.
Fresh coffee from your favorite café or roaster is a rich and complex experience. Wait a few weeks though, and what was once vibrant is now a little boring. It’s flat and lacks character, like most members of the symphony couldn’t be bothered to show up, and the dominant flavors are trying to carry the tune by themselves. It’s gone stale.
First, it’s helpful to know what we’re trying to achieve when we’re storing coffee. To keep it fresh, of course. But what does that mean? Well, there are two important pieces of chemistry that are happening after coffee is done roasting.
The coffee is degassing. The volatility of the roasting process produces quite a bit of carbon which is released from the coffee in the form of CO2. This process has a positive impact on coffee flavor for two reasons: first, CO2 is slightly sour (think of unflavored soda water) and the more CO2 leaves the coffee the less it covers up the coffee’s flavor. Second, CO2 repels water, actively reducing the amount of extraction in the brewing process. As a result, coffee that is very fresh can taste overly bright, sour, and salty. The rate of CO2 loss is dependent on a host of factors, and it can take up to 3 months for a coffee to lose almost all its CO2.
The role of CO2 in brewing is why a “bloom” is often recommended in manual brewing methods. Prewetting the coffee grounds encourages the coffee to release its CO2, allowing us to access flavor more efficiently. In very fresh coffee you will notice the grounds swell up and bubble as the CO2 escapes.
This doesn’t mean that coffee’s peak freshness is the point of CO2 depletion because there is another simultaneous process occurring: oxidation. During oxidation, coffee is releasing its volatile aromatic compounds into the air. These compounds, of which there are nearly 1000, are responsible for the vast flavor complexity we find in coffee.
With an understanding of degassing and oxidation, a picture starts to come into focus. As CO2 levels decrease flavor improves, and while oxidation increases flavor degrades. So, coffee tastes best when it has been allowed to sufficiently degas enough CO2 but oxidation has not yet absorbed too much coffee flavor. For most coffees peak freshness is typically in the 10-14 day window after roasting. The rate of degassing and oxidation are contingent on roast level, origin, bean density, the type of roaster used, and more, so this does not mean that coffee outside of a 14 day window is bad. Rather, simply that flavor changes over time.
The goal of storing coffee is to mitigate oxygen exposure and limit oxidation while allowing the coffee to degas CO2. The most important thing you can do is store your coffee in an airtight container somewhere cool and dry, as both heat and moisture accelerate oxidation. Jars are great, and there are many designed for coffee storage that allow you to flush the oxygen out of the vessel.
Often it is fine to store coffee in the package it came in. Our 12oz bags are resealable and have a one-way valve that allows released CO2 to escape without letting oxygen in. Additionally, they are flushed with nitrogen, an inert gas that doesn’t bind with coffee’s volatile aromatics so that the coffee inside is fresh as can be until that bag is opened.
If you’ve purchased more coffee than you can use in 2-3 weeks then getting that coffee somewhere cold can be helpful, but there are some things to look out for if you’re going to do so. I mentioned earlier that that heat accelerates oxidation so it follows that freezing it would grind staling to a halt. There are a few problems though: most home freezers don’t get cold enough to completely stop oxidation, and if we aren’t storing the coffee properly coffee can take on flavor from other items in our freezer (in my house that’s peas and chicken stock). Also, the dryness of freezers can cause condensation to form on the coffee if we aren’t careful. So, if you only have enough coffee to last a couple weeks leave that valuable freezer space for ice cream. It’s a win-win.
If you have a lot of coffee and want to store some of it in the freezer to slow the staling process make sure it’s in an airtight jar or bag and leave it there until you need it. Once opened just leave the coffee out at room temperature, sealed of course. It’s tempting to put the coffee back in the freezer while you work through the bag but moving between warm humid air and cold dry air promotes condensation.
Have a question or a topic you’d like to see covered? Shoot us an email at [email protected], or tune in to the livestream Wednesdays at 10:30am, Brian will be taking questions in the chat!