Coffee Degassing Experiment 3 – Ground vs Whole Bean

Experiment three was a chance to apply all of the lessons learned in measuring CO2 degassing of roasted coffee.

Degas 3 Setup

Lesson 1: A photo copy stand was used to support the graduated cylinders. Fill the cylinders with water and place upside down in the tank. Lower the photo rack then support the cylinders with square wooden rods, hold with several rubber bands then raise the attached cylinders with the camera holder adjuster.

Eye Droppers on Tubing

Lesson 2: Using eyedroppers is very effective but you have to slightly point them downhill or the air will escape, just slower. The most effective dropper has a turn on the end pointing down. This made it easier to prevent gas escaping and water filling the line. The eye droppers were purchased at Walmart for $2 a pair. Keep the eyedroppers as close to the cylinder bottom without touching. Water pressure becomes a factor if you put them deep in the water.

Flask with Funnel on Scale

Lesson 3: The critical timing is from grinding the coffee, place in the flask, weigh and stopper. By putting a funnel in the flask on the scale ground coffee could be scooped quickly and accurately.

Lesson 4: I wrote a trivial program to log the time vs the readings. This meant recording readings was just typing in the levels. The program tracked the time. For the time value I used a Unix Timestamp, the number of seconds since January 1 1970 00:00:00 GMT. So to calculate offset is simple subtraction from the first reading. The data was then copy/pasted into a spreadsheet for calculations and graphing.

Costa Rica Degas Exp 3 w Degas 2 in Background

Lesson 5: Track as many variables as possible. By using Artisan I could compare degas roast 2 to degas 3 roast.

Hours Ground ml CO2 Whole ml CO2
30 0
0.05 45 0
0.10 58 0
0.12 62 0
0.13 66 0
0.18 75 0
0.20 80 0
0.27 90 0
0.34 100 0
0.44 110 0
0.51 118 0
0.53 120 0
0.65 130 0
0.75 136 0
1.04 154 0
1.17 160 0
1.28 165 0
1.76 183 15
1.94 190 18
3.79 226 37
11.69 270 89
12.12 280 94
22.12 290 124
23.36 290 126
24.04 290 128
24.58 294 130
25.61 296 132
27.25 296 135
35.65 296 145
36.87 296 154
46.35 300 170
47.62 178
48.65 182
50.75 182
59.44 188
60.89 194
72.75 198
85.32 210
91.38 220
100.10 227
108.91 236
111.60 240
114.28 243
117.01 246
120.31 248
155.70 264
157.01 267
166.09 270
Hours vs ml CO2 Ground (Blue) vs Bean (Red)

Conclusion 1: Ground degassing is pretty well complete in this experiment at 12 hours. 280 ml of CO2 released at 12 hours while 300 by 48 hours. After day 3 the whole beans are still degassing but slowing down.

Next experiment is to repeat this setup but with a medium roast (430o drop.) I also ordered a school grade color spectrometer and am investigating roast colour analysis.

Most Important Conclusion: Crawling into the raw science basics of roasting is really fun.

Ground vs Whole Bean Degassing

In this experiment, I roasted Costa Rica coffee to Full city. I dropped the roast at 450oF. While I normally do not roast so dark, I knew from documentation this would result in more CO2 to be released.

Ground on left vs Whole Bean on Right

I placed 100 grams of ground coffee in the the left flask, while 100 grams of whole beans were placed in the right flask. I loaded the ground coffee into the flask as quickly as possible, but the degassing speed surprised me. In one hour of capping the flask, 120 ml of CO2 was already released. This is much faster than whole bean degassing. In the previous whole bean experiment with a medium roast and twice the coffee it took 24 hours to release 120 ml.

Degassing CO2.

Another change from the previous setup was to add eye droppers to the end of the tubes. This made it easier to see the bubbles form. Play the video to see how fast the ground coffee released CO2.

Eye Droppers on Tubing
Hours ml CO2
0 0
0.08 28
0.13 40
0.23 58
0.27 62
0.28 65
0.35 72
0.38 78
0.45 84
0.52 90
0.60 96
0.67 102
0.80 110
0.90 116
0.95 118
1.00 120
1.07 126
1.15 130
1.37 138
1.48 144
1.88 158
2.00 160
2.30 166
3.13 186
3.53 194
5.00 212
6.83 228
8.78 238
19.00 256
31.00 268

ml CO2 Released vs Hours

Roast profile from the Artisan tracking screen.

Costa Rica Roast Profile for Degas 2 Experiment

Degassing Grind w 1/16" Scale

This shot image was captured with a Celestron digital microscope. The scale on the right is 1/16″. The beans were ground with a Macap MC4.

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.
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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.
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