One weird thing about strength is that the difference between strong coffee and weak coffee is quite small in terms of the percentage of TDCS. For example, most people here in the United States would consider a cup that contains 1 percent TDCS and 99 percent water too weak and a cup that contains 2 percent TDCS and 98 percent water too strong. Most “good” cups of coffee fall somewhere between 1 and 2 percent TDCS, although it’s always up to personal preference.
The second part of evaluating extraction is yield (sometimes called extraction yield or solubles yield), and it’s a bit hairier to explain. Yield is a way to measure extraction, and it refers to the amount of material that the water has removed from the actual coffee grounds. Think of it like this: if you have a pile of coffee grounds, you are starting with 100 percent coffee material. The maximum amount of coffee material that is physically possible for hot water to remove (extract) is somewhere around 30 percent, and that would likely bear an utterly disgusting cup. Coffee professionals usually aim to extract somewhere between 18 and 22 percent of coffee material from the grounds.
Coffee that has a low yield (less than 18 percent of the coffee material has made its way into the cup) usually tastes underextracted, and coffee that has a high yield (more than 22 percent of the coffee material ends up in the cup) usually tastes overextracted. This all comes back to time: the longer that water and coffee mingle, the more opportunity there is for extraction.
The Takeaway
Your tongue can tell if your cup is over- or underextracted. In general, underextracted coffees lack complexity (meaning you are unable to taste multiple distinct flavors in the cup) and are often sour. Their aromas are normally faint and/or simple, and their bodies are thin. Overextracted coffees are often overly bitter and astringent (drying), which hides the yummy flavors in the cup. Their bodies are usually thick and syrupy. The best cups tend to be somewhere between under- and overextracted and are more likely to offer a range of pleasing flavors.
The Coffee Brewing Control Chart
For you visual learners, the Coffee Brewing Control Chart can help you wrap your head around strength and yield, which can help you understand how to correct over- and underextracted coffee until it’s just right. How do coffee makers know what “just right” means? An MIT chemist named E. E. Lockhart developed the Coffee Brewing Control Chart in the 1950s to try to answer that question. He surveyed a bunch of US coffee drinkers about their preferences and found that most people prefer coffee that falls in the “ideal” square shown on the chart: an extraction yield between 18 and 22 percent and a strength measurement between about 1.15 and 1.35 percent. Lockhart’s original findings are still supported by the Specialty Coffee Association (SCA) today—although these general preferences can vary around the world. While it may seem counterintuitive, you’ll see that it is possible to brew a cup of strong, underextracted coffee and a cup of weak, overextracted coffee (actually, the latter describes typical diner coffee).
COFFEE BREWING CONTROL CHART
Brewing Ratio: Grams per Liter
There are ways to calculate strength and yield with special tools and math (as indicated by the numbers on the chart), and it’s tempting, even for professionals, to try this—but I’m not going to tell you how to do that here. It’s nice to be aware of the ranges described in the chart, but I can’t emphasize enough that you shouldn’t let numbers distract you from taste. There is a sentiment among some coffee professionals that measurements like these encourage folks to stamp a cup of coffee as “good” based on calculations rather than taste. However, numbers don’t tell the whole story—a bunch of different factors affect how coffee extracts, including the type of coffee, the processing method, and the roast. This means that even if two coffees have the same yield—20 percent, for example—they could still taste very different from each other.
The upshot of understanding how strength and yield work is that you will be able to experiment with both measures in your home brew. In order to do that most effectively, you’ll need to understand the different brew variables that affect strength and yield—brew ratio, grind size, contact time, water, and temperature. These are the building blocks of every coffee recipe.
BREW RATIO AND DOSE
If you’re going to make coffee, you need to know how much coffee and water to use. When I first started making coffee at home, I literally just guessed how much to use based on vague memories of what I had seen others do. If optimizing your cup is your goal, I don’t recommend this method. Instead, you should consider two things: (1) how much coffee you want to end up with and (2) your personal preferences for strong or weak coffee.
Your brew ratio—the amount of coffee to water you use—has a direct effect on the strength of your cup. Remember, strength refers to the concentration of coffee compounds present in the brew, which affects the mouthfeel of your coffee, or how it feels in your mouth. The more coffee to water you use, the stronger your coffee will be. The less coffee to water you use, the weaker your coffee will be. The more coffee you start with, the more compounds end up in your cup.
Brew Ratio and Taste
High brew ratio (too much coffee):
thick mouthfeel, muddled flavors, very aromatic
Low brew ratio (too little coffee):
thin mouthfeel, weak flavors, faint aroma
Lots of people will tell you that the correct brew ratio is two tablespoons of ground coffee for every six ounces of water. For his part, Beethoven reportedly counted out 60 whole beans for each cup of coffee he made. You can start with either of these tactics if that’s easiest for you, but I (and most professionals) use a slightly different method of measuring coffee because consistency—being able to replicate desired results—is key, and the methods described earlier are not consistent.
The two-tablespoons method requires ground coffee, and if you are using fresh whole beans, you won’t be able to measure until you grind them, which can be wasteful and expensive (high-quality beans aren’t cheap). Beethoven’s method removes the waste factor, but beans can vary greatly in size. Sixty beans from one type of coffee plant may end up providing significantly fewer grounds than 60 beans of another type of coffee plant. The solution? Use a brew ratio based on weight in grams.
Most coffee professionals in the United States use a brew ratio between 1:15 (that’s 1 gram of whole coffee beans to 15 grams of water) and 1:17 as a starting point. That will get you close to the “ideal” range on the Coffee Brewing Control Chart. Yes, this means measuring both beans and water by their weight, instead of by their volume, which is what you’re likely familiar with. Still, measuring both items with a single unit of measure means you can simplify this stage of the process by using only one piece of measuring equipment—an inexpensive kitchen scale.
How Much Does Accuracy Matter?
I know a lot of you will choose the two-tablespoons method, and that’s fine. But for next-level brewing, I highly recommend measuring by weight and using a brew ratio for three reasons:
•It’s more accurate.
•It makes it easier to troubleshoot/adjust your cup.
•It accounts for the variability in devices.
What some people may not realize is that the actual mass of the amount of coffee that fits inside a measuring spoon can vary greatly. Despite what you may have heard to the contrary, that’s not something coffee people have made up to be complicated; it’s science. It’s why experienced bakers tend to measure by weight. One cup of all-purpose flour might not be the exact equivalent of the next cup you measure; maybe you inadvertently packed the second cup more, meaning there was more mass in that cup than in the first. Even a bit too much flour in baking can lead to less-than-ideal results.
For coffee, there’s even more room for inconsistency. I already mentioned the fact that different coffee beans can vary significantly in size (just look carefully at your next bag of blended beans). This means the mass of one tablespoon of this bean might differ from the mass of one tablespoon of that bean. I
t’s like the difference in weight between one cup of all-purpose flour and one cup of whole-wheat flour. These masses can differ by a gram or more, which is significant when you are dealing with relatively small measurements. Additionally, if you are measuring coffee grounds, the grind size also comes into play. A tablespoon of finely ground coffee will certainly have a different mass from a tablespoon of coarsely ground coffee. When the difference between your perfect cup and a not-as-good cup can be half a gram or less, it’s critical to get exact measurements. The same is true for water—a tablespoon of water is supposed to weigh about 14.8 grams, but try weighing tablespoons of water and see how often that ends up being the case.
Measuring by weight, however unfamiliar, is the only way to ensure precise, consistent brew ratios and consistent cups. Otherwise, you may luck out with a delicious cup, but it will not be a result that’s easily replicated unless you record the ratio for future use. After all, coffee has only two ingredients—even small variations affect the taste. When you do something consistently, it makes it easier to know what to adjust, if need be. For example, if your coffee feels quite thick and overwhelming in your mouth (strong), you might be using too much coffee, and next time you can use less. If it feels too watery (weak), you might be using too little coffee, and next time you can use more.
Lastly, ideal brew ratios vary depending on the device you are using. As you’ll see in the next chapter, devices are specifically designed to optimize extraction, but their designers have different ideas about how to go about doing that. How your device works to extract coffee can certainly affect the brew ratio (or ratios) that tend to work best with it.
How to Calculate Dose
The amount of coffee that’s used in a brew ratio is called the dose. Calculating dose requires math. I hate math because in sixth grade I failed my advanced placement test, but my teachers decided to advance place me anyway, which prompted a six-year struggle through AP classes that I’m clearly not over yet. But even I can calculate dose. And the good news is that once you figure out your dose, you can use the same numbers over and over again without having to calculate anything! The other good news, which I mentioned before, is that my brew ratios let you measure both water and coffee by weight in grams, which makes things very easy. Huzzah metric system!
The first things you need to know are what size your brewing device is and how much coffee you want to end up with. (Don’t under- or overfill your device—choose one that’s the proper size for the amount of coffee you want to brew.) Let’s use a small BeeHouse dripper as an example. The manufacturer says it is designed to hold grounds for one to two cups of coffee. Let’s say you want one cup. One cup is eight fluid ounces. One fluid ounce of water is 29.57 grams. Let’s start with a 1:16 brew ratio and see what that means for your coffee dose (to make things easier, I’ve rounded all of the measurements to the nearest whole number):
Since you already have the calculation for the 16 part of the ratio (237 grams), all you have to do is divide it by 16 to get the coffee dose. That ends up being 15 grams (actually about 14.8, but I find it easier to adjust my dose if I start with whole numbers). This means you would start with 15 grams of coffee beans and 237 grams of water, grind, brew, and see how that tastes. Depending on what you think of the taste, you can adjust your dose accordingly, half a gram or so at a time. (As a heads up, 15 grams might be a lot more coffee than you’re used to using. One of the most common mistakes of people making coffee at home is not using a big enough dose. If you try using a 1:16 brew ratio and think your dose looks like too much coffee, I urge you to follow through and see what happens before reducing the dose.)
You can also apply the chart to different quantities and different devices. If you were brewing for a crowd using a large Chemex, you could use the chart to see that you would start with 1,419 grams of water and between 83 and 95 grams of coffee beans to brew six cups. However, if you own multiple devices, note that you likely will not be able to use the same brew ratio across all of them. As you’ll see in chapter 6, the ratios I use vary from 1:12 to 1:17, depending on the device.
Once I figure out the brew ratio I like for the device I’m using, I write it down and use it each time I make coffee. Most craft coffee shops do too, and that ratio becomes part of the device’s base specifications, or base specs. The point isn’t to reinvent the wheel each time you brew. Instead, you can use the base specs as a starting point. A coffee shop might adjust its specs daily (or at least every time they’re working with a new batch of coffee), a process called dialing it in, in order to optimize quality. At home, I rarely tweak mine. The base specs usually work well enough.
Choosing the Right Dose
Bad: Guessing
Okay: Two tablespoons of ground coffee per six ounces of water
Better: 1:15 to 1:17 whole beans to water in grams
GRIND SIZE AND CONTACT TIME
Grinding coffee involves breaking whole coffee beans into smaller pieces. A whole bean, with its relatively small surface area, does not afford water much opportunity to penetrate it and extract the good stuff. Also, trying to extract coffee from whole beans would take forever, which isn’t practical. That’s why beans are ground up into big (coarse) or small (fine) pieces before being used—it makes it easier for water to extract coffee from them. Understanding how grind size affects extraction will help you adjust your cup to suit your preferences.
Grind size has a significant effect on your coffee’s extraction and, by extension, its flavor. Finer grounds give your dose a greater overall surface area than coarser grounds, which translates to more room for water to flow in and extract flavor. This means that if you start using finer grounds without changing anything else about the way you currently make coffee, you will end up with a higher extraction yield than usual. When water has more opportunity to penetrate the grounds and dissolve the coffee’s flavor compounds, more dissolved material ends up in your cup.
Of course, more isn’t always better. Because extraction happens faster with finer particles, you can easily overdo it. Brewing methods that use finer grounds tend to require less contact time with the water to make a yummy cup. Likewise, brewing methods that use coarser grounds tend to require more contact time with the water.
While finer grounds may extract faster, they don’t necessarily help the coffee brew faster. This is because grind size can drastically affect flow rate, or how quickly water passes through a pile of coffee (this applies to pour-over brewing methods more than full-immersion brewing methods; see page 46). Coarse grounds have more space between them, which means water can pass through them more quickly. Finer grounds are more compact, so water moves through them more slowly. Think of it like this: Would water travel faster through a column of gravel or a column of sand?
Unfortunately, there isn’t one special grind size that will guarantee you a better cup; great (or terrible) coffee can be made with all manner of grind sizes. To make things more mysterious, there are no universal grind sizes and no standardized language to talk about grind size beyond the terms fine, medium, and coarse, which are highly subjective. Further, different grinders come with different nomenclature. One grinder set to 14 might not produce the same size grounds as a different grinder set to 14. Other grinders may not even use numbers. There are scientific ways to measure particle size, but you need extra equipment, and it simply isn’t practical for the home brewer (or anyone).
GRIND REFERENCE CHART
For these reasons, it’s often simpler to compare the size and texture of the grind with more familiar kitchen items, like salt and sugar. In the Grind Reference chart above, I’ve illustrated the spectrum of grind sizes, along with a tactile comparison and the brewing devices covered in the next chapter that typically use each size.
Different devices generally work best within a certain range of grind sizes to better control the flow rate. If you use grounds that are too coarse for a device, the water will pass through them so quickly that you’ll end up with underextracted co
ffee. On the other hand, if you use too fine a grind, the water will move through the grounds at a snail’s pace (or even stop!), and you’ll end up with overextracted coffee. This is why, if you’re in a rush, you can’t just tighten the grind to make your coffee brew faster.
One big indicator that your grind size is too fine for your device—at least if you’re using a pour-over device—is the state of your coffee bed: if it looks muddy, the grind is likely too fine. Another indication is your water takes too long to draw down through the coffee bed. In chapter 6, I provide a target drawdown time for each of the pour-over methods. Overshoot that time and your grind might be too fine; finish ahead of schedule and your grind might be too coarse.
Devices also tend to be associated with certain windows of brewing times. A French press is among those with the longest brewing times and an AeroPress is among those with the shortest brewing times. That isn’t to say there is a single correct combination of grind size and contact time for each device, even if the manufacturer says otherwise. You can find multiple ways to make a great cup of coffee on one device; it’s just that success is probably more easily obtained in the windows described in the chart—at least for beginners. However, some devices are more versatile than others. For example, this book provides specs for both an eight-minute and five-minute French press method, and the coffee community seems to crank out endless wild recipes for the AeroPress.
It’s important to note that grind size is never truly uniform because roasted coffee beans, by their nature, break up irregularly. All grinders produce a distribution of grind sizes, from relatively large chunks to tiny fines. This is one of the reasons why it’s important to use a good grinder (and why I suggest that if you buy only one coffee implement, it should be a burr grinder), but I’ll discuss this further on page 84.
Craft Coffee Page 3
