7 Days, 1 Coffee Experimentation
Welcome to my little experiment on daily coffee. This topic came up after one of my customers asked, "Does coffee taste different every day after opening a bag for 7 days?" Personally, I have never brewed the same coffee consistently right after opening a bag. I usually have a variety of beans and often enjoy experimenting with different coffees each day.
This time, I decided to brew the same coffee for 7 days using the same tools to minimize variables and measure each brew with a coffee refractometer daily. For this experiment, I used Sopa Omkoi, a washed coffee from Chiang Mai, Thailand, with Boston water TDS 000, OREA V3 MKII Brewer, X Series M Glass from Brewista, Momentum from IAMNOTBARISTA, and Stagg EKG and Sally Scale from FELLOW.
Recipe and Process:
Coffee: 15g
Grind Size: Medium
Brewer: OREA V3 MKII with Kalita Wave 185
Water: 93'C (Boston tap water with ZEROWATER: TDS 000)
Ending Time: ~2:00
|  Time (s) |  Add Water (g) |  Total (g) |
| 0:00 | 50 | 50 Circle Pour |
| 0:30 | 60 | 110 Circle Pour |
| 1:05 | 70 | 180 Center Pour |
| 1:40 | 70 | 240 Center Pour |
I brewed the coffee using the following recipe for 7 days plus one additional week after opening:
- Day 1-2: The coffee had a sharp acidity and lacked uniformity and balance, but the aroma was the best of all the days.
- Day 3: The coffee became brighter, sweeter, and more refined in its acidity. The flavor continued to improve in sweetness and balance while the aroma decreased.
- Days 4-7: The coffee's sweetness increased, the flavor became more uniform and balanced, and the acidity remained dedicated. The aroma continued to decline slightly.
Throughout the experiment, I measured the TDS (Total Dissolved Solids) of the coffee daily, which averaged about 1.41%. Initially, the coffee had a sharp acidity, but as days progressed, it became sweeter and more balanced. I believe that once a bag of coffee is opened, the beans begin to stabilize as they interact with the environment, resulting in more consistent flavor from day 3 onwards.
Environmental Factors: I could not control the weather, and there were 3 days of rain with high humidity. On these days, the coffee tasted noticeably sweeter. This observation made me pay more attention to how weather changes, particularly rain, affect the coffee’s flavor.
Adding a Variable: On the last day, I introduced a new variable to the brew by adding AQUACODE to the water to reach 90 ppm. The result with 0 ppm water was sweet and similar to day 6, emphasizing sweetness. However, with 90 ppm water, the coffee became more acidic and highlighted stone fruit flavors.
- 0 ppm coffee: TDS at 1.42%
- 90 ppm coffee: TDS at 1.41%
For those who enjoy acidic coffee, adding minerals can enhance that flavor profile. Over the 7 days, I found that coffee becomes sweeter and less acidic as it ages. If you prefer less acidity in your coffee, aged coffee might be ideal.
Summary: In summary, I found that coffee gets sweeter and brighter while its acidity becomes more refined after opening a fresh bag. The more it ages, the sweeter it gets. This might explain why many roasters recommend waiting about 14 days for degassing or even a month before the coffee reaches its peak flavor. Some even suggest waiting up to 2 months, especially for certain premium coffee varieties.
For the Sopa Omkoi coffee, I found that it reached its best flavor around 30 days after roasting, becoming extremely sweet with a delicate acidity. This was a fun experiment, and I learned a lot from this session. There's always more to learn about coffee, and I hope you enjoyed this experiment and the insights it provided.
Interested in trying the same experiment? You can order Sopa Omkoi from Newbery Street Coffee Roasters, a local Thai specialty coffee roaster in Greater Boston.