How Long After Roast Date is Coffee Good For?

How Long After Roast Date is Coffee Good For?

What Does Coffee Roast Date Mean?

The roast date simply tells you when that particular batch of coffee was roasted. The roast date should be stated clearly on any bag of specialty coffee. If you can’t find it, ask the retailer or roaster–but that may be a red flag, since this is a basic piece of information that’s important for knowing how fresh a coffee is. Roast date serves as an indicator of the optimal window of time for consuming the coffee. While coffee doesn’t ‘expire’ per se, it will eventually reach a point where it becomes nearly flavourless.

How Long Does Coffee Last After Roast Date?

Technically, coffee ‘lasts’ forever. Your coffee beans aren’t going to evaporate–they will still be there, sitting in the bag. They are also unlikely to grow mould. Instead, the question we want to ask is how long coffee can be considered ‘fresh’ for after it’s roasted. Or in other words, what is the optimal consumption window for roasted coffee?

Important note: In this piece, we are referring to whole coffee beans. We always recommend buying whole beans and grinding just enough each time you prepare a tasty beverage. Ground coffee will lose its flavour much faster, as we will explain below.

Coffee Freshness After Roasting

By freshness, we mean that the coffee has not become stale, which happens through a process called oxidation. Oxidation happens to almost everything, as an effect of the oxygen present in the atmosphere. Since coffee is an agricultural (‘living’) product, it’s particularly subject to oxidation, just like most other foods. Oxidation is involved in fruit ripening, rust forming on metals, and even the ageing process of our bodies. It’s natural, but we want to work with that knowledge to drink coffee while it’s at its peak flavour.

For roasted coffee, we would measure ‘freshness’ from the roast date (not when it was harvested or processed). So on the day it’s roasted, that coffee is technically the ‘freshest’ it will be. However, in the case of coffee, fresher doesn’t necessarily mean better. That’s largely because roasted coffee contains CO2 gas trapped inside the beans. Too much CO2 interferes with the extraction, so it's best to be patient and allow the CO2 to escape naturally, in a process known as degassing—which we’ll get into next.

We like simplicity, so here's the direct (and somewhat simplified) answer:
Coffee should be left to degas for the first few days after its roast date.
After that, the coffee will be at its peak, shining in all its glory, for ~5 weeks.

Coffee Roast Date, Degassing, Freshness Custom Graph

*The graph above is an oversimplification on many fronts. But the idea is that, the best time to drink the coffee–its peak flavour–is when the brown line is above the green line; from about a week to up to 2 months after its roast date.

Important note: This time window is only an approximation! Different coffees will degas slightly differently, depending on the bean, the darkness of the roast (lighter roasts take longer to degas), the type of roaster used, and other factors that we won’t get into here. This info is just meant to serve a rough yet practical guide to help you when buying coffee beans.

One key takeaway we’d like to highlight is this:
Coffee can be at its peak for quite a while after it's roasted. There’s no need to buy the absolute freshest coffee, nor to discard the bag that was roasted a few weeks ago.

Let’s see how we might use our new knowledge of roast date when heading into Abyss to restock our home coffee supply.

How to use Roast Date When Buying Coffee

It’s really simple – most coffee will be at its prime between ~1 and 8 weeks after it “was roasted. An example:

So, I just woke up and realised I’ve run out of coffee. Bad. I need more. Now. Today, the 26th of March. So I waltz into Abyss, spend 15 minutes browsing the amazing selection, and finally decide on Ethiopia Genji Challa, since I love washed Ethiopian coffees for my V60.

I pick up a bag, flip it around, and see that it was roasted yesterday, March 25th. Oh, so fresh! But suddenly, I remember reading this article, and then I consider that I want to drink this coffee as soon as I get home. I understand that these beans would be okay today, but the coffee hasn’t had time to degas, and it won’t yet display its full potential cuz that pesky CO2 is gonna get in the way. So I pick up another bag – also roasted yesterday. Then I pick up another, and voila! This one was roasted last-last week, on March 15th. That’s 12 days ago – almost 2 weeks. While I might not want to buy a sandwich that was made 12 days ago, this coffee is perfect right now. It’s in its prime. Also, since my partner and I drink a lot of coffee, I know that this bag will only last us a week, or 10 days at most. So we’ll definitely finish it while it’s still optimally fresh. Bingo–this is the one!

Now we’ve got the practical side covered. But you might still be curious–what’s the deal with this ‘degassing’ thing? Time to get a bit more technical.

Degassing Beans: The Science Behind Roast Date

Degassing means letting trapped gas out of something. Here, we are talking about CO2 gas (carbon dioxide) trapped inside of roasted coffee beans. You might be wondering how the CO2 gets in there in the first place. Basically, it’s created as a byproduct as complex molecules are broken down into smaller molecules during the roasting process. The CO2 gets released from within, but lots of it remains stuck (temporarily) inside the hard coffee bean. The gas will slowly escape over time, until the point where it no longer interferes with the extraction.

Degassing coffee is important because, for the flavours to come through, the level of extraction needs to be just right. During extraction (brewing), the hot water penetrates the coffee grounds, grabbing all sorts of molecules–like caffeine and tons of aroma and flavour components–and brings them into the final cup. If there’s too much CO2 present in the coffee, the heat will accelerate its release, and it will counteract the extraction as it escapes and pushes the water away from the good stuff.

It’s said that too much CO2 in the coffee masks its flavours. That’s precisely because it prevents the water from penetrating properly, usually resulting in under-extracted coffee, which would tend to be sour. In Tim Wendelboe’s podcast with Malin Borgås, he uses the metaphor of overly fresh coffee being blurry and unclear, like before you put your glasses on. Once the degassing process has been allowed to proceed for long enough, the CO2 gets out of the way and allows the clarity of the flavours to be extracted fully.

Can we speed up or slow down degassing?

The short answer to this is that you don’t need to. You can just leave the coffee beans in their original bag, on the counter, and degassing will proceed at its natural pace. If you were to store the beans in the fridge (not recommended) or freezer, the cold would slow down the process. If you were to heat it up or leave it out in the sun, it would accelerate it (also not recommended, since it will also greatly speed up oxidation and ruin the flavours). Opening the bag will not speed up the degassing of the beans, but putting the beans in an airtight container might slow it down just a bit. But what about grinding?

Freshness of Ground Coffee vs. Whole Beans

We know that CO2 is trapped inside the bean, slowly being released, and that too much of it gets in the way of the extraction. But won’t it just all escape instantly upon grinding? Grinding will, indeed, release a lot of the trapped CO2 However grinding isn’t really a substitute for the natural degassing process, since lots of CO2 can still be trapped. Remember, we are talking about the molecular scale, so even very fine espresso grounds can have CO2 trapped inside the coffee solids.

Grinding your coffee all at once (for example when you buy the bag) accelerates the degassing process. This is not directly “bad,” but lots of the good flavour compounds are volatile (meaning they evaporate and fly away), so they also leave with the CO2. This doesn’t happen to the same extent during natural degassing, since many of those molecules aren’t as volatile as CO2 (which is a gas) and don’t sneak out so quickly.

Further, grinding significantly speeds up the oxidation of the coffee. As the bean is ground into fine pieces, the surface area increases exponentially, allowing the oxidation process to happen much more quickly. This combination of accelerated oxidation and accelerated evaporation of flavour components means that the peak flavour window for the coffee can be shortened from 2 months (for whole beans) to just a week or two! Again, this is only a rough approximation, and other factors might play into your decision here–see next.

Light roast coffee beans

Grinding Coffee Beans at Home vs. Buying Ground Coffee

So, in an ideal situation, we would want to buy roasted coffee as whole beans, let it degas for a few days if it’s super fresh, measure the amount we need, and grind it just before brewing. If you don’t have a grinder at home, but you frequently spend money on quality coffee and brew it at home in a nice machine, investing in a grinder might be a good idea. Skipping that step while investing in the rest is sort of short-changing the cup quality you can achieve at home.

At the very least, we want to avoid those electric “spice grinders”, as they just ravage the beans and crack them up into randomly sized pieces, making the extraction messy. Instead, we always want to use a burr grinder, which methodically crushes the coffee into more consistent grounds. A handheld burr grinder will cost you the same as ~2 bags of coffee, but is a major upgrade from a spice grinder. It might also be better than buying ground coffee, depending on your situation. If you tend to drink the coffee really quickly–like within a week–and you’d rather not invest in a grinder or do a daily wrist workout, the upside is that the grinders behind the bar are professional-grade, and will generally achieve a more consistent grind than entry-level burr grinders. But if you sometimes drink coffee out, making one at home only sporadically (so the bag lasts you 6 weeks), you might notice the cup quality gets less and less impressive. Grinding on the spot would extend the peak of the coffee quite a bit.

Conclusion

Tl; dr: Coffee contains lots of pressurised, trapped CO2 right after it’s roasted. By resting the coffee, it is allowed to degas, and the CO2 escapes naturally. After a few days to a week, the CO2 will no longer interfere with the extraction, and the freshly roasted coffee will be in its prime for up to 2 months after that (assuming it’s whole beans). Ground coffee will oxidise more quickly, and should be consumed as quickly as possible to enjoy its full flavour profile. Consider investing in a decent burr grinder if you drink lots of coffee at home, so you can buy whole beans and enjoy the coffee at its peak for longer.
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