As I looked into the idea of how to test and improve cold-brewed iced coffee, I decided that I wanted to approach this systematically exploring all the variables affecting the brewing of coffee. I essentially wanted to go “back to formula” and really explore each of the variables and how they affect cold-brewed coffee. There are 24 variables that affect brewing according to the SCAA’s “The Basics of Brewing Coffee”, which is basically an abstract version of Lingle’s Coffee Brewing Handbook. The variables are broken down below by 3 major categories, which I modified slightly from the official dichotomies and nomenclatures:
Coffee Beans
1. Ratio of blend components
2. Bulk density of beans
3. Chemical composition of beans
4. Methodology of roasting
5. Rate of roasting
6. Degree of roast
7. Rate of degassing
Brewing
8. Average size of particles
9. Size distribution of particles
10. Particle shape
11. Time of water contact
12. Contact temperature
13. Temperature gradient during brewing
14. Complete wetting
15. Uniform flow
16. Particle movement
17. Method of separation
18. Degree of clarification
19. Length of time and method of holding
20. Holding temperature
Other
21. Coffee ratio (weight)
22. Water ratio (volume)
23. Water composition
24. Water treatment
How can this little bean be so complicated!?
Yes, that is a lot of variables. While it might be tedious fun to meticulously measure each variable, I believe some variables don’t really need to be tested but held constant (i.e. water treatment or rate of degassing) and some could even be grouped together (average size of particles, size distribution of particles, and particle shape are all related to grind and can be practically tested together). Also, I plan to split all the variables in 3 stages of trials where the first stage will progress sequentially and the other stages will be held concurrently and/or after the first stage, as time permits. Here is the outline of the stages along with a potential timeline:
The 3 Stages of Testing
Stage 1 – Refining the Brew Method – 10 weeks
I plan to brew 5 samples of cold-brewed coffee each week, 1 sample serving as the control which will be unchanged throughout stage 1 and 4 samples adjusting the same variable 4 different degrees. The difficulty will be keeping the other variables constant, particularly Coffee Bean variables, but I will go into detail in a future post as I discuss stage 1.
Stage 2 – Creating the Perfect Bean – 4 weeks
This stage is dependent on my current schedule of my roaster apprenticeship. I am currently learning how to roast by spending time roasting and asking questions at Cartel Coffee Lab and Cortez Coffee Company. These guys have been awesome and so helpful and I can’t thank them enough for putting up with me as I hang around their roasting. Understanding the roast process, selecting/grading greens, and improving my cupping sensory skills will probably take a few weeks to get to the level I am comfortable for the project. Once I feel confident in my understanding of the beginning half of seed to cup, I can start to test these variables and begin on stage 2.
Stage 3 – Fringe Science for Cold-Brewed Coffee – 4 weeks
Like the show “Fringe”, I plan to explore some areas where coffee usually doesn’t tread…
During stage 3, I plan to test some of my crazy unconventional ideas for iced coffee. I will do these experiments as time and resources become available but I think this is where I experiment with non-traditional methods and the results may be unwieldy. Here are some of the ideas I would like to explore:
-Introducing high pressure with cold water to cold-brew by the cup on demand, aka the cold-brew clover
-Using reverse osmosis and adjusting the membrane to produce a super concentrate cold-brew (special thanks to George from Spectrapure for the idea)
-Infusing cold-brew coffee with fruits, spices, and herbs simliar to fruit-infused vodkas
-Use molecular gastronomy to change textures and introduce extreme temperatures with liquid nitrogen
-Blending hot-brewed coffee with cold-brewed coffee attempting to capture the best elements of both
-Exploring robusta beans and if they have application to cold-brewed within specialty coffee
-Using a paint shaker to boost turbulence and extraction time during the brew stage
Finally I wanted to discuss how I will measure the results of the tests. Ultimately, the final and most important metric is the taste. Taste trumps all! However, taste is intrinsically difficult to quantify and calibrate among different people and taste palettes. As far as quantitative results, I will be using a refractometer from ExtractMojo which will measure the TDS (total dissolved solids) and yield of the coffee samples. I will also be using a grind analyzer hand sieve from QAQC to calibrate grind size throughout the tests. For taste, I will be conducting blind cuppings of samples at Cartel Coffee Lab, Cortez Coffee Company, and my church, all of which I think is a broad spectrum of tastes preferences and palettes, from professional cupper to ordinary coffee drinker.
. I was going to post each head-to-head match but instead I’ll just show some of my favorites and you can browse all the latte art in the gallery below. In the end, I think the best baristas met at the finals, Ashley from Cartel and Greg an independant. Ashley ended up taking the win but it was a very close competition overall.
