Five Variables of Brewing Coffee

For many of us, coffee is an essential part of our day that always stays the same. It turns out that coffee is also an incredibly complex beverage. Before coffee reaches you in its roasted form, it has gone through many hands. Everything from the soil, to the processing method, to the roasting method will contribute something to the flavor of your coffee. When you buy a bag of coffee, much of the flavor has already been determined by these factors. However, brewing is the final factor that contributes to how the coffee will taste. And, of course, whether or not you add milk or sugar.


One of the most helpful things when brewing coffee at home is to remember that there are 5 basic brewing variables that impact its outcome. These variables must all work together or else you’ll end up with an imbalanced cup (think sour or astringent). These variables are water temperature, grind size, brew time, agitation, and the ratio of coffee to water.


Water temperature refers to the temperature of your brewing water. The basic principle here is the hotter the water, the faster the brew time. A great example of this is cold brew. Because the water is room temperature or fridge temp, the brewing process can be slowed to take place over many hours. When brewing hot coffee, it’s recommended to heat your brewing water to 195º-205ºF. 


Grind size refers to how fine or coarse you grind your coffee. Because a finer grind produces more surface area of coffee to extract, you would use a faster brew time for a very fine grind. For example, espresso utilizes a super fine grind, and it typically takes about 30 seconds to brew a shot of espresso. Because the coffee has been ground so fine and because of the pressure (or agitation) being applied as it brews, it takes much less time to extract the coffee. 


Brew time, as you’ve seen in the above paragraphs, is the time it takes to actually brew the coffee. How long you decide to brew your coffee will rely heavily on the other variables. If you are brewing a french press with a coarse grind, you might take 5 minutes to brew the amount of coffee that would normally take 3 minutes in a V60 with a medium grind. 


Agitation refers to the amount of movement that is enacted upon the coffee during the brewing process. This could be the pressure exacted upon espresso or the water flowing through the brew bed of a pour over or drip brewer. Every brew method utilizes at least a small amount of agitation. An example of a high agitation brew method is espresso. Manual pour overs and drip brewers also utilize agitation throughout the brewing process. Lower agitation brew methods are french press, aeropress, and cold brew. All of the lower agitation methods have at least one moment of agitation, usually an initial stir of the grounds to make sure they are fully saturated. The higher the agitation, the less brew time you need. 


Ratio of coffee to water refers to how much coffee you’re using in relation to how much water you’re using. This variable will usually be static with the rest of the variables changing to adjust the flavor. For example, when brewing a pour over, you might keep a ratio of 16 parts water to one part coffee but change the brew time, grind size, and water temperature throughout testing the recipe. On the other hand, when brewing espresso, it’s more common to adjust the amount of coffee being used for a shot and keep other factors such as brew time the same. 


It’s difficult to talk about one variable without discussing how it interacts with another. A good thing to remember is if you’re increasing one variable, you might need to decrease another. These variables are helpful in such cases where you’re using a new brew method. For example, if you’re using an unfamiliar drip brewer on vacation, you know that the agitation, brew time, and water temperature are determined by the brewer, so you can adjust the way the coffee tastes by changing the grind size and ratio. If you’re testing a recipe, it’s good to adjust one variable at a time so you can decipher the changes each make in the final product. 


Learning about these variables made brewing coffee so much easier for me, and I hope it will do the same for you. Let us know what you think in the comments below! 

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