Welcome to our final day. Day 30 of 30! It has been a long and bumpy ride but we’ve made it in one piece. Obviously the plan was to have this post finished quite a while ago, but somehow the world never seems to slow down enough. Regardless, you have made it here with me. Congrats on your survival. I originally intended for this post to be a sample chapter of the book I have been working on, though I should have known that it would take longer to write a book than I expected!

To start off today I want to talk about a few things that have been going on in my world. First of all, I’m super excited to talk about what I have been experimenting on for the upcoming book, so today’s post will touch on that, even if it isn’t as deep as I wanted.  Next, we finally have a new WBC champion in Dale Harris from the UK! I met him in Seoul, and he is going to be a great representative of Specialty coffee. Lastly, though certainly not least in my mind, I’ve been working on a very limited coffee roasting subscription which I intend to launch in January (It’s a new venture, so there are some nerves to be sure). I’ll talk more about that soon as well.

So let’s get going.

If I have to sum up the book I am working on, I would tell you it is “my take on brewing” or “useful methods to make better coffee”. In reality it is a combination of good old fashioned brewing methods combined with specific correlations to each brewing parameter. It is important to point out that this first book will be strictly focused on filter brewing, and espresso will be featured in my following book endeavor. The reason I have been testing and researching a lot is to prove, disprove, or evolve my theories. Even the best ideas need refinement, and I feel that I have finally gotten enough results to put everything into a proper method. I will be talking about some things you are familiar with; the specific brewing parameters and techniques are not going to blow your mind, but the reason why they are used and how they specifically correlate to coffee extraction may very well surprise you. 

The book will also include detailed experiments for you to follow so you can experience the specific flavor impacts that different parameter changes have on coffee. The intention behind this is to not only show you my methods, but also to give you active experience in correlating brewing variables with flavor changes. This can give you a much deeper understanding of coffee brewing in the long run. 

In order to perform many of these experiments at home or in your own cafe, you will want some equipment such as a variable temperature brewing kettle (or a highly accurate thermal probe), pour-over drippers (I like 2 hole beehouse ceramic), white paper filters (NEVER use unbleached in my opinion), consistent water (distilled water + Third Wave Water is an easy option), a couple scales with resolution to 1/10th gram, decanters, and a good quality grinder (I prefer a Guatemala Lab). After equipment we have to establish consistency in methods. If you are using a ceramic dripper it needs to be preheated to roughly the same temperature each time, if you are manually pouring water you need to pour at the same speed, with the same grind contact and water flow. The idea is that every variable is controlled as much as possible so that you can see the results of changing the parameter you are focused on. Of course it is best to brew your variant experiments as close together as possible so you don’t have massively different temperatures between brews in the end, but depending on your investment or available equipment that may not be possible, so you would need to keep detailed note logs. 

An interesting thing that this research and theory evolution has done for me is to see just how inadequate the use of TDS refractometers is in brewing coffee. You can refresh yourself on my thoughts about refractometers here. I have been coming to the realization that the TDS and extraction yield are direct reflections of: 1) the grind size 2) the brew ratio, and 3) (a bit less) the extraction time. 

This is interesting to me because it is often assumed that any variable in the brewing can radically change the TDS, which I have been finding to be incorrect. Now don’t get me wrong, any change in variable will change the overall extraction itself, though not necessarily the actual TDS. 

One of the big ideas I had that lead me to this book was the thought that everything in the coffee extraction can be directly tied to energy. Thermal energy (the temperature of the brew water) and kinetic energy (turbulence, water pour rate, stirring, etc) should, in theory, be able to manipulate the extraction significantly.

Here is the interesting thing.

These energy inputs DO in fact change the extraction, but DO NOT change the TDS and extraction numbers significantly. I have gotten identical TDS and yield results for numerous brews which have had large changes in thermal energy as well as the flavor itself. So our standard measurements for coffee are failing the test big time, at least for the majority of the reasons they are used in the first place, and it tells me that we need a new measurement (which I have been saying for a long time). 

In the mean time, I am trying to develop the best methodology and systems that will help us not only extract coffee better, but be able to analyze what exactly we are getting in the cup from a sensory point of view. We are a ways off from having a truly useful measuring device for brewed coffee though. Maybe the acceptance that the current methods are inadequate will push us as an industry to find a new metric? Time will tell…

I want to leave you with an experiment that I have used numerous times now, so you can try it for yourself. 

You will need the equipment I discussed above. Ideally 3 of each brew device and variable temperature kettles should be used so that all brews can be done in fast sequence. Here is the method:

  • Measure 3 – 20g doses of whole bean coffee (use a different dose and ratio if you like, but make sure all brews are identical)
  • Grind each dose separately on the same grinder, with the same setting. Doses should be ground separately to ensure a similar amount of fines production. Sifting the grinds for this experiment is not necessary, but it can add another layer of consistency.
  • Set your kettles for 195f, 200f, and 205f (90.5c, 93.3c, and 96.1c)
  • Prewet the filter and heat your brew device immediately prior to brewing
  • Brew each batch of coffee using the same pre-wet time, pour rate, and method. Keep everything identical other than the water temperature. I recommend using a 1:16 ratio, which is 320g of water for the 20g dose.
  • If you are going to use a refractometer, be sure the measure the final brew weight immediately after brewing each batch. Set aside a portion of each finished brew and measure the TDS % after the samples are fully cooled. Plug all of your measurements into your app to get the yield and strength (or do the math if you like that sort of thing)
  • While your TDS samples are cooling, taste each batch of coffee side by side. Tasting blind is unnecessary for this experiment, as the purpose here is to experience the impact in flavor that each temperature brings. 
  • Your TDS and measurements should be very, very close or identical. The primary reason I have found for variance in TDS/yield on this test is from slight differences in the amount of fines from grinding. 

In my experience with this particular test, the lower temperature brew may be less “full” in flavor, and the higher temperature brew may be more over-extracted and tannic. However, some brews do better at high temperatures and some do better at lower temperatures. I believe I have found the reason for that, but you will just need to pick up the book to find out.

Until then, happy brewing!

Pete