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Updated for 2021
If you talk to most coffee experts, they’ll tell you that the age of your beans has a huge effect on the end product in your cup. But how important is it really to use fresh beans?
AJ from Whole Latte Love ran an experiment to test the effects of time and different storage methods on coffee beans when being used for espresso.
Using a fresh, 5-pound bag of Fuego Coffee Roaster’s Ethiopia only 5 days from roast as the test subject, AJ tested to see how beans age over 30 days when left in a bag, an air-tight container or put in a freezer.
What AJ looked for during this experiment was how a 30-day time period changes extraction time, appearance, and taste. What he discovered might surprise you.
On day 1 of the experiment, AJ opened the bag of Fuego Coffee Roaster’s Ethiopia and immediately set aside some of the beans in a Coffeevac air-tight container. These beans stayed sealed for the duration of the 30 days as a control for the experiment.
AJ also measured out 15 individual doses of 18 grams and put them in the freezer.
The rest of the beans stayed in the original roaster’s bag. This is not ideal storage in the real world, but for the sake of this testing, AJ hoped it would highlight, or even expedite, the effects of aging.
As is the case with any controlled experiment, the goal was to maintain consistency.
AJ chose all of his equipment with that in mind to minimize variables in extraction. By single dosing with the Ceado E37SD grinder, he ensured there were no leftover grounds from the previous day.
Using an Asso The Jack Leveller provided consistent distribution and compression without inconsistencies in tamping pressure or technique.
AJ also chose to use an ECM Synchronika with PID temperature control, again to ensure consistency from shot to shot. Shots were pulled in a temperature-controlled room at the same time of day to minimize even slight variation in humidity or other factors.
To check the retention on the grinder, AJ measured 18 grams of whole beans with an Acaia Pearl Scale and added one small squirt of water with an RDT sprayer to moisten the beans and control static before grinding.
He measured his output at 18 grams for essentially zero retention. This process was repeated a few times, always with .1 gram more than or less than of variability.
AJ used an Acaia Lunar scale on the drip tray with a timer set to start when it registered the first drops of liquid. The goal throughout the experiment was to dial in a 2:1 brew ratio of 18 grams in to 36 grams out in 25 seconds from first drip.
The E37SD is a dedicated single dose grinder from Ceado, designed for use with all methods of coffee preparation. Its massive 83 mm titanium coated burrs produce consistent grinds with near zero retention. The included barista tools are designed to eliminate static for perfect dosing.
A scale for the pro, the barista, and the discerning coffee lover at home, the Acaia Pearl offers precision you could only find in a lab. Now, cafes the world over are coming to rely on this scale to deliver cutting-edge results in the cup.
AJ's first shot was a bit too fast so he adjusted to a finer grind and pulled another one. This got him closer, but now the shot pulled a little too slow. After a couple more shots and adjustments, everything checked out.
He stirred his glass, took a sip and noted the dose, time, and taste in an extraction log, which served as a reference point for the rest of the experiment.
AJ then pulled two more shots to make sure he was right on with grind size before taping down his quick set gear knob to avoid accidentally changing it at any point.
Past experiences led AJ to believe that as beans age but kept at the same dose, you generally have to grind finer to get the same extraction time. To quantify this change, he decided to leave his grinder untouched at the initial grind setting for the duration of the experiment and measure the difference in time it takes to get as close to a 2:1 brew ratio of 18 grams in to 36 grams out when manually shutting off the pump.
AJ then proceeded to pull a shot with the same technique everyday for the rest of the month. After each shot he noted the time and taste. Right off the bat, the results were not what he expected.
He anticipated the extraction would get faster and faster as the days went on. Instead, the first few days were wildly inconsistent. First 25 seconds, then 41, then 26, then 53. For the next week, the time actually increased, indicating that his grind was too fine, even though he hadn’t changed anything. At this point he started to worry that he was going to choke the machine and ruin the entire experiment. But, after day 10 things started to turn a corner and extraction times began steadily decreasing again.
It's worth noting that from day 15 on, AJ took his entire set-up out of the office and recreated it at home. This was due to having to work remotely with the COVID-19 pandemic ramping up in the middle of the experiment.
For the next week, shot times were faster, falling between 30 and 35 seconds, and the large, inconsistent swings experienced early on were stabilized. The final 9 days of testing resulted in a steady, consistent decrease in extraction time, which confirmed AJ's initial expectations.
AJ came to the conclusion that when looking at extraction time vs. bean age, the first half of the month was much less consistent than the second. There was a clear point when extraction time turned a corner and started decreasing, which also resulted in a shrink in variances and more consistent shots for the remainder of the experiment.
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As for appearance, the results were far from earth-shattering. Any small variations throughout the month were likely due to the differences in extraction, rather than the time having a direct impact on the appearance.
That said, the crema on the shot pulled on day 1 had noticeably more depth and color compared to the older beans. This makes sense considering fresh-roasted beans retain a large amount of CO2 before degassing as time goes on.
The last thing AJ noted throughout the experiment was taste. It's important to mention that when shots were improperly dialed in, such as the days when the extraction times exceeded 1 minute, the taste was wildly different. Additionally, different roasts and batches will behave differently, so these results only relate to this specific test.
On day 1 of the experiment, the espresso was very bright, acidic, sour, and almost overpowering, which was expected of beans that fresh.
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As the first week went on, some of the sourness started to fade away and was replaced by sweet, fruity, and tangy tastes. On day 10, AJ noted hints of bitterness. This was also the day of the longest shot pulled during the entire experiment, so much of the bitterness can be largely attributed to over extraction. As extraction time started to come back down, sourness started returning in the form of sharp and tart flavors.
Day 16 was when AJ took note of what he considered (at the time) to be the best shot of the experiment, citing a great balance of brightness and full-bodied flavor.
As extractions continued to stabilize, some of the early bright, tangy, and grapefruit flavors returned. Over the following week, the acidity toned down, and AJ felt like he was drinking a more balanced and enjoyable, less overpowering, version of the shots pulled on the first few days.
By day 28, the fruit flavor had faded a bit and the results remained that way for the final three days of tasting.
In summary, the tastes varied widely throughout the month, but seemed to be tied more to extraction time than the age of the beans.
From a subjective standpoint, AJ's favorite tasting shots were pulled on days 21-27. On those days, the flavor profiles seemed the most mature and balanced without being overwhelming.
In this experiment with these particular beans, 1 month was not long enough to make the espresso taste old or stale, even when stored in the original paper bag.
So, can you freeze coffee beans?
AJ revisited the beans he set aside in the beginning of the experiment, which remained sealed or frozen over the course of the 30 days.
He first wanted to see how, without adjusting the grinder, their extraction time compared to the bagged beans.
That evening, he took the frozen beans out to thaw, but left the bags sealed. He also left two bags in the freezer to test grinding them while still frozen.
The next morning, AJ started with the now-thawed beans. With all other factors identical to the rest of the experiment, he pulled two shots; both in 36 seconds. In comparison to the paper-bagged beans which pulled a shot in 27 seconds the day prior, something was definitely different.
Based on the length of the shots pulled from the paper-bagged beans over the course of the month, the thawed beans after 30 days in storage pulled shots at the same level as days 2-4, day 16, or day 22. Based on this, it does appear the freezer did something to slow aging of the beans.
When AJ stirred and sipped the shots pulled from the thawed beans, he noted the taste was very sour and reminiscent of the first few days of the experiment. This led him to believe that the "age" of the thawed beans were closer to days 2-4 of the experiment.
As for the still frozen beans, AJ pulled two shots and the extractions came in at 36 seconds and 32 seconds. They tasted identical to the shots from the thawed beans.
For the final storage method, the air-tight container, two shots were pulled in 36 seconds and 37 seconds. These times were essentially the same as the frozen and thawed beans and the taste was similar, but with better balance and an acidity toned down to a tolerable level.
The very last part of the experiment was to stop comparing apples to oranges when it came to taste. For the first time in a month, AJ changed the grinder adjustment knob.
He dialed in the three different storage type samples back to the experiment's ideal brew ratio and time of 18 grams in and 36 grams out in 25 seconds, and compared the taste of all three.
This much more closely resembled a real-world scenario of keeping your grind dialed in for your current beans and conditions, and where the tastes could be accurately compared.
The bagged beans tasted about the same as at the end of the experiment, which makes sense considering the tests ended with a 27-second extraction time.
The beans from the air-tight container tasted incredible. The flavor was rich and balanced with sweet and tropical fruit flavors. For AJ, this was the best shot of the entire experiment.
Last up were the frozen and thawed beans. While they didn’t taste vastly different from the previous shots, they were still a bit too bright for AJ's liking. Advocates of freezing coffee note that the cold temperatures slow the rate of CO2 degassing and oxidation within the beans.
While freezing beans may be helpful for storage periods much longer than 30 days, it didn’t appear to do much during this experiment. One reason for this may have been that that the beans were put in the freezer before they had a chance to sufficiently degas and got locked in at a premature, overly-sour stage before flavors could fully develop.
This process answers some questions, but also leaves the door open for more experiments, such as longer time periods or different roasts. If you have an idea for something you’d like us to test out let us know!
For even more tips, check out our video on How to Keep Coffee Beans Fresh: A 30-Day Espresso Experiment.