I often come across as an idiot to politely smiling and nodding coffee aficionados, burrowing in the retail display for the very freshest batch; “Yes, that is the most recent roast date we have. It's funny, I would actually recommend drinking our coffee between two and five weeks after it's been roasted. We find it tastes sweeter and more balanced once it's been rested.” Their eyes glaze over and a grin spreads across their face. How can coffee be too fresh? They think I'm trying to get rid of old stock. I don't blame them. At face value it doesn’t make any sense. The idea is counterintuitive. How can anything be too fresh? I’m frustrated that I'm unable to communicate, in a brief conversation with a customer, everything that needs to be said about this topic. So, let's dive into it in the hope that you can make more discerning choices when it comes to purchasing a bag of beans.
Fresh coffee isn't always a good thing
In a world where freshness is invariably a good quality, this sounds questionable - freshness is a tagline that many food businesses use to sell their products. Coffee businesses are no different; many coffee shops boast about having freshly roasted beans because that is what they think customers want to hear. And they do.
Surely a consumable product is best enjoyed immediately after its creation and, as freshness declines, so does the enjoyability of the product? We’re familiar with the opposite effect in alcohol; whiskeys and wines that just get better and better with age. Coffee, however, behaves like neither and both of these at the same time.
During the roasting process, raw coffee beans more than double in size, whilst losing around 15% in weight. This creates a cellular structure that is more porous which allows carbon dioxide gas, produced during the cascade of chemical reactions that is the roasting process, to escape from the coffee. After the coffee is roasted it begins degassing. I have learned from many unpleasant experiments and unfortunate logistical issues that you don't want to drink coffee, brewed in any fashion, during this process. I have tried roasts less than twenty four hours old as both espresso and filter and I will spend the rest of my life wishing I hadn't. Exquisite notes of grass and gas abound.
How long is the degassing process?
It depends on the roast level of the coffee. The more roasted a coffee is, the more porous it becomes, causing the degassing to happen faster. This is perhaps a reason why coffee freshness has been emphasised; coffee has historically been dark roasted, causing it to degas and therefore go stale quicker. However, even the darkest roasted coffee is not best consumed directly after roasting. Brewing dark roasted coffee as a filter, you may find a sweet spot between a few days and two weeks old. Contrastingly, a very light roasted coffee may not even start tasting good until up to two weeks old and will still remain tasty seven or eight weeks after its roast date.
Using medium roasted coffee brewed as a filter for an example, coffee enjoyability versus freshness can be mapped with a Bell Curve. Immediately after roasting, coffee is not enjoyable. Arguably around the five day mark, enjoyability increases slightly. Between one and four weeks, enjoyability suddenly peaks. It tapers off slightly from four to five weeks before decreasing dramatically from six weeks on. Coffee drunk as filter eight weeks off roast or more can still be enjoyable. Many coffee drinkers will not notice the difference. Those of us who have had their enjoyment of slightly sub par coffee ruined by endless meticulous experiments with roast dates will notice a fading of aromatics and a diminishing vibrancy after 6 weeks, particularly where acidity is concerned.
How do we brew coffees differently as they get older?
Over time, a coffee will appear to change its flavour characteristics. You may get different tasting notes drinking a coffee as it ages. This is not a result of the coffee itself changing its cellular structure, but in fact all to do with the science of how coffee is extracted. If there hasn't been sufficient time for the coffee to degas, the hot water will have to do extra work to remove this gas before it can dissolve the compounds we are trying to extract.
Coffee has three major groups of compounds in it, from most to least soluble; fruit acids, Maillards compounds and dry distillates (including caffeine). A coffee that is well extracted will have a good balance of all three. A coffee that is under extracted will have an unfavourable amount of fruit acids dissolved and will taste unbalanced. Similarly, a coffee that is over extracted will have an unfavourable amount of dry distillates and also taste unbalanced.
We know that coffee which is not sufficiently rested will more likely be harder to extract than a well rested coffee with the same brewing recipe, due to the presence of the carbon dioxide gas. Preferably, you should wait until your coffee is within an ideal time frame to use. However if you’re in a situation where you only have coffee that's too fresh and you’re really thirsty, you need to extract your coffee more in order to get a better brew. Using more water (and/or hotter water if possible) and a longer brew time, perhaps by finening your grind setting, will help ameliorate this issue. If you are brewing the fresher coffee as a filter, allowing more time to bloom (pouring hot water on it for the first time and allowing more gas to escape) is another way to lessen the “green” flavour in your cup.
Considering the way coffee ages, the inverse is also true; a coffee that has aged too much will be prone to over extraction. Some coffees can appear to become sweeter and more full bodied over time when using the same recipe. As the coffee ages, the less soluble compounds become easier to extract due to the absence of gas, making them more prominent in the balance of coffee solids dissolved, making it seem as though the coffee has become more sweet, bitter, more full bodied and less acidic. To counter this effect, when finishing off those last scraps of bag that are a bit on the old side, apply the reverse method. Less water, cooler water and shorter brew times (perhaps using a coarser grind) will give you a result closer to the taste of using your original recipe with age-appropriate coffee.
But what about espresso machines?
When brewing with a conventional espresso machine, you don’t have the luxury of blooming a coffee and removing gas that way - instead, hot water is applied with relentless force onto the coffee. If the coffee hasn’t been degassed it can be a real mess. Large bubbles may sputter violently out of your grouphead (espresso machine handle) as their only means of escape. This natural disaster will translate into the cup. Espresso is more concentrated and intense tasting than filter, so this only exaggerates the ghastly gassy flavours.
With this in mind, it's important that not only is coffee used for espresso roasted darker than its filter counterparts, but also that it is very well rested. We prefer to brew our medium roasted espresso between three and four weeks off roast, compared to between two and three weeks for the lighter roasted filter coffe (which takes longer to degas). If you’re inclined to really dark roasts, you can probably start brewing espresso between ten days and two weeks after that date on the bag. However, you might find they begin to go stale as early as four weeks.
I hope this information pops into your head the next time your coffee jar is emptied, the next time your gaze wanders over to an enticing retail display. Consider what brew method you’re using, what roast level the coffee is (baristas should be happy to tell you) and how long you think it will take you to get through the bag before making an informed choice. I believe that this is the best recipe for delicious coffee.