I realized the other day that we’ve been in radio silence here on the night kitchen blog. Some is because of a chicken run project we’ve been doing at home in addition to my regular day job and work at the roaster. Some, particularly talking about making coffee, is because I’ve been reluctant to take on the topic. But, here goes.
Coffee is an extraordinarily simple beverage. You can almost think of it as a 2 ingredient soup. While there are any number of different ways to brew coffee, ultimately the brew is a mixture of coffee solids dissolved in a liquid, usually water. In the 1950’s, MIT chemistry professor E. Lockhart started looking at defining what goes into a good cup of coffee. There are two primary factors that go into how you perceive coffee in the cup.
First is the Total Dissolved Solids (TDS). This is a measure, in parts per million, of how much of the soluble matter in the coffee is dissolved during the brewing process. TDS doesn’t directly relate to the strength of the coffee but the mouthfeel, or body of the coffee. French Press will have more of a mouthfeel then a pour over.
The second factor is the extraction yield. This is a measure of the weight of the coffee solids that are dissolved. The extraction yield, as a percentage, is shows how much of the ground coffee was dissolved and ends up in the cup.
The two terms are interrelated but different. Think of it this way, the percentage of TDS is a measure of how strong or weak the coffee is. If the TDS is below 1.15%, the coffee is colored water. TDS above 1.55%, black tar. The extraction yields is a bit more nebulous but really measures the flavor of the coffee. The ideal extraction yield seems to be between 18% and 22%. Without the right amount of TDS, you can’t get the best out of the flavor but you can have a perfect strength coffee where the flavor is underdeveloped. Here’s the data shown as a chart from the SCAA (Specialty Coffee Association of America). This version is the ‘American’ standard. European’s typically like more body (more dissolved solids) in the cup.
If you want, you can make a similar chart showing coffee body by brewing method. Espresso and French Press, because of the brewing methods, have the highest amount of total dissolved solids. Siphon coffees have the lowest amount of total dissolved solids. Percolators, drip brews, and pour overs fit in the middle. Within each of the different brewing methods, the flavor of the coffee can be developed differently within each of the brewing methods.
Sounds like a science project doesn’t it? There are actually gizmos out there (technically a refractometer) along with an app that will let you exactly measure the TDS and extraction yield. I’ve never used one and probably won’t. I prefer to use my sense of smell to drive the show.
Remember earlier I talked about coffee as a simple soup – the analogy through the science of brewing still holds. The secret is making sure you give yourself the best chance to dissolve the good ones and leave the bad tastes behind. Here are the four rules –
- Get good coffee. You want coffee that was roasted recently, less than a month old usually. Grind it right before you use it.
- Get the right balance of water to coffee. For a standard 40 oz (usually listed as either an 8 or 10 cup pot) home brewer, I will use approximately 2 ounces of ground coffee. That puts our coffee at home into the upper right hand corner of “ideal” in the chart above. Note here that I am working in weights for the coffee.
- Brew at the right temperature. For hot coffee, I prefer the water to be between 195 F and 200 F. Much higher and more bitter compounds come out, colder, and the coffee flavor doesn’t develop as well. Cold brew coffee is an exception as are the rules for espresso.
- Make sure you have the water in contact with the coffee for the right amount of time. A 4 minute brew cycle seems to be about right. Whether I’m using a French Press, pour over, or looking at my coffee pot, I look for a 4 minute brew. Espresso, Aeropress, the Bialetti Moka pots have their own rules for time.
For most of us, items 1 and 2 above are the only ones we can change. Unless you are doing pour overs on a daily basis, you get the time and temperature that your machine gives you. So, experiment with the coffee and the balance of coffee to water. Keep notes on what you like and don’t like. It’s also worth investing in a small kitchen scale. We use ours constantly and not just for coffee.
If you are in Denton and get in touch, we would be happy to meet up and talk about coffee. Good coffee is simple to make, it takes a small amount of attention to detail.
Life really is too short for bad coffee.