Measuring Roasted Coffee CO2 Degassing

As I read more and more on how CO2 is released from freshly roasted coffee I decided to try my own experiment. Basically the experiment is to measure the captured CO2 as it is released. A basic experimental approach is to use an eudiometer.

Eudiometer as shown in Wikipedia

My setup is not quite as elegant.

First Degas Measurement Experiment Setup

The purpose of this test is to try the setup. The flask is 500 ml with 211 grams (~7.4 oz.) of medium roast Costa Rica coffee. The beans were loaded 5 minutes after dump with a temperature of 94oF. The graduated cylinder is 250ml and the tubing 1/4″ OD flexible copper. I am concerned that the inside diameter is large enough that air will escape up and water flow down. I will add a water dropper on the next version to keep water from going in and the air bubbling out. Also the tube should be shorter so that it is easier to get into the graduated cylinder.

12 hours into degassing
Hours ml CO2
1.4 20
3.7 29
11.7 76
13.0 80
19.0 100
22.0 112
24.0 122
24.6 124
26.0 129
36.0 152
37.0 154
46.5 172
48.0 176
49.5 180
59.5 194
61.0 200
71.0 214
84.0 224
94.5 236
104.3 246
108.0 250

ml CO2 Released vs Hours

The papers I found said the degassing would continue on whole beans for 7 days. Now that the output reached 250 ml, the capacity of the graduated cylinder, I am going to end this experiment and set up one comparing whole bean and ground coffee. To avoid the 250ml capacity I will put in 100 grams of coffee.

Vacuum Bagging Fresh Roast Coffee Beans

On the commercial coffee LinkedIn group, there was a question on vacuum packing freshly roasted coffee to keep it fresh. When I was at roasting school, we learned how freshly roasted coffee gives off CO2. This is why you need a can or bag with a gas relief valve. Recently, I decided to get a hand vacuum bagging system. It is a low-cost unit available in Canada from Home Hardware for only $20. For a small cost I could experiment with vacuum packing coffee. The bags are reusable but not cheap, at about $1.25 each. As I just want to use the bags for my coffee at home, the price per bag is not a factor. If the coffee was for resale, a much lower cost per bag would be needed.

Vac N Store system from Home Hardware

The Vac N Store kit comes with three bag sizes. My sample roaster does 1/2-pound roasts that fit nicely in the small bag. By sealing the bags, the coffee is not exposed to oxygen, which is what contributes to making coffee stale. What surprised me was how much gas is released by the beans. Here is a bag of just-sealed, freshly roasted coffee. The little hand pump does a fair job of removing air, but is not commercial grade.

Vacuum bagged coffee

Here is the bag 5 days later.

Vacuum bag with released CO2

I was surprised how much air was in the bag. This is not from leaking. Here is a large bag of decaf green coffee beans that I packed several weeks ago. The vacuum seal is still tight.

Decaf Green coffee beans in vacuum bag

I put the bagged roasted coffee in my grinder this morning, and it was very nice. Did it hold the freshness better? I am not sure. I need to do a side-by-side on the same coffee, one roasted a week ago and stored, the other roasted the day before.

My question coming out of this is how do companies like Illy vacuum pack coffee? I believe theirs stays tightly packed because the coffee is ground. Perhaps on the next roasting batch, I will bag 1/2 as beans and in a second bag, 1/2 ground and see how it compares.

Down to Earth – Started by Mother Nature, finished by hand

Walking around the village
A year ago my wife and I spent a week at the Down to Earth Coffee Plantation in Dota/Costa Rica. While I have been trained to roast green coffee beans I had no idea how coffee was grown or harvested.

We learned about everything from planting seeds to transplanting, picking, processing, drying and milling (removing the parchment).

This is an opportunity to experience Costa Rica. We lived in the local village of 300 people 45 minutes by 4×4 from the paved road.

Weighing and Hulling (Removing the Parchment)

When the beans are at 11-12% moisture, they are removed from the parijuelas and bagged. Each bag has the parijuela number that it came from. The bags are then weighed and the results logged.

Weighing and logging the dry beans

Coffee beans have a hard shell covering the bean. Here is the coffee bean anatomy introduced in the Processing the Coffee Cherries article. This illustration from Wikipedia shows the cherry anatomy.
Continue reading “Weighing and Hulling (Removing the Parchment)”

Drying the beans

Wet Coffee Beans just from the cherry

The product of coffee cherry processing is bags of wet coffee beans. These new beans are about 2/3 water. Green beans ready for roasting need to be 11 to 12% moisture, so a significant amount of water has to be removed.

While large commercial processors will use a power unit, small operations use the sun. Beans are spread out to dry. Most spread the beans on a concrete pad; Matias uses drying racks called parijuelas, traditional wood-framed mesh racks.
Continue reading “Drying the beans”

Artisan – Visual Scope For Coffee Roasters

Martin from Sweden emailed me a few weeks ago about an open source software package for graphing roasting profiles. With the trip to Costa Rica, my work on software was delayed. This morning I loaded up the software and tried it. I was really impressed.


I have written software for graphing roasts from my HH506RA data logger connected to a computer and my HotTop roaster. My work focused on my hardware setup. When I built the coffee office I installed a small PC with the monitor acting as both TV and computer monitor. One of my plans was to use the monitor to track roasts.

Roasting with Artisan Program Monitoring

The software is available for PC, Mac and Linux. Continue reading “Artisan – Visual Scope For Coffee Roasters”

Processing the Coffee Cherries

Once the cherries are picked, the beans are removed and then dried. Processing involves separating the coffee beans from the cherry.

Beans removed from the cherry

Removing the beans from the cherry can be done in several ways:

  1. Ferment-and-Wash Method
  2. Machine-assisted Wet Processing
  3. Dry Process

Ferment-and-Wash is used mainly at large coffee processing factories. On the farm, the crop was processed with the machine-assisted wet process. Cherries that were too small to be machine processed were rejected, then dry processed by hand. Continue reading “Processing the Coffee Cherries”