While we took a break last week to highlight relief efforts for the Nashville Tornado over on our Facebook page, we’ve been in the midst of a series where we’re talking about what you need to brew great coffee at home. Check out part one and part two here.
Coffee-making, as we’ve learned, doesn’t have to be over-complicated. If you don’t own café-grade equipment in your kitchen, you can still achieve café-quality results with products under $150. So, now that you have the tools you need to make your coffee, let’s dig into the science behind making coffee.
For those of you who didn’t do so well in high school chemistry (like me), it may be intimidating looking at formulas, reactions, and really anything to do with science stuff. When it comes to coffee science, all you really need to understand in your at-home coffee making is that different parts, aka variables, of the equation cause different results. The final product of the combination of variables is what we like to call extraction.
What is extraction exactly? Simply put, extraction is the act of pulling the good stuff out of your coffee grounds using water. In extraction, there are five different variables that you can manipulate in order to influence how your coffee is brewing.
Dose refers to the physical weight of the ground coffee being used while you’re. Adding more coffee would slow down water as it passes through the coffee, which increases the perceived body and mouthfeel as well as time, but decreases extraction assuming you haven’t changed other variables. The opposite is true if you add less coffee; water spends less time with the coffee, which lowers extraction.
This refers to the total contact time of water and coffee, best understood as contact time. Contact time can be separated into two portions: pour time and dwell time. Pour time refers to the given amount of time that you are adding water to the coffee. Dwell time refers to the amount of time following pour time to when water is no longer in prolonged contact with the coffee. Longer dwell times will equal more extraction, while shorter dwell times will equal less.
Grind size is the most common of the five variables that you will change in our brew bar setups. It refers to how large or how small your coffee grounds are. A finer grind or smaller coffee particle size will increase surface area. Increasing the exposed surface area will increase extraction. Conversely, a coarse grind setting will decrease the exposed surface area of the coffee, thus decreasing extraction.
Temperature refers to how hot the water is that you’re using to brew coffee. The ideal coffee brewing temperature range is 202°F – 205°F. While you can experiment by increasing or decreasing your brewing temperature, you’ll generally find the best results when you use this range.
Agitation (turbulence) is exactly what it sounds like: disturbing the coffee by any means. More specifically, it refers to the speed and velocity in which your water is coming in contact with the coffee. As an isolated variable, more intense agitation will result in extracting more. In contrast, a pour that is nearly motionless with a slow flow rate close to the bed would produce very little extraction compared to the aforementioned “intense” pour style.
There are two kinds of agitation you can employ when brewing: natural and manual. Natural agitation is influenced purely by how you’re adding water to the coffee. This includes pouring patterns and how fast or slow you’re pouring water. Manual agitation, however, is the means by which you influence agitation through external methods. This includes swirling the coffee bed before and/or after brewing and stirring using a spoon.
Water quality varies greatly depending on geographical origin, local water treatment, and in-house filtration. Calcium, alkalinity, pH, and sodium impact how readily compounds are extracted from coffee, so it’s important to know what’s in your brewing water. In order to ensure that you have great brewing water at home, one of the easiest solutions is using Third Wave Water. Their mineral packets are specifically designed to dissolve into distilled water to create the most optimal water chemistry for your brewing needs.
Putting It All Together
As you gain control of these variables, you can harness them and adapt them across the different types of brewing methods. Each kind of brewer requires different applications of time, turbulence/agitation, and grind size since each brewer is designed to produce different results based on shape, material, and filter design. There are two kinds of brewer designs that you’ll regularly encounter as you do your research: flat bottom and conical.
Flat Bottom Brewers
Like your standard Mr. Coffee or a commercial-grade batch brewing machine, flat bottom brewers hold coffee at a uniform density/depth throughout the entire brewer/basket, which means that the coffee is evenly distributed. Flat bottom brewers bring out heavy sweetness and substantial body from the coffee, allowing for a higher perception of strength. When brewing with a flat bottom brewer, you do have to increase agitation to make sure that all the coffee has a chance to interact with the water.
Conical brewers are much more forgiving when brewing. Methods V60’s and Chemexes allow for water to funnel to one single exit point, giving coffee more of a chance to interact with water as it drains down. Conical brewers typically produce more balanced results, allowing for a structured presentation of the notes associated with the coffee. Depending on your recipe, you may need to reduce agitation as well as use a finer grind size.
I’ll admit: on paper, there’s a lot that goes into making coffee. But, as we’ll see next week, it’s not all that difficult! We’ll share our favorite ways to brew coffee!