Within the species coffea arabica, which produces the vast majority of high quality coffee, there are a large number of varieties. As consumers have become more interested in the nuances of coffee flavor, more attention has been given to the effects of plant variety. Here are some of the major coffee varieties, which you might see listed on your bag of coffee.
Typica - Historically the most commonly grown coffee variety, Typica is the coffee against which all other varieties are judged. The ancestors of modern Typica originated in Yemen, but in the 17th and 18th centuries were taken through India to Java, then sequentially to Amsterdam, Paris, and Martinique, before being exported to Latin America, Brazil, and Africa. Now grown worldwide.
Bourbon - In the 18th century, a mutation of Typica was found growing on the island of Bourbon (now known as Reunión, located off the coast of Madagascar) which was higher-yielding and more disease-resistant than Typica. Bourbon is also known for its sweetness and citrus-like acidity. Now grown mainly in Central America, especially in Guatemala and El Salvador.
SL28 & SL34 - Bourbon plants were also exported to Tanzania, then Kenya by French missionaries. Of these French Mission Bourbon varieties, two were selected by a coffee research institute, Scott Labs, as being of particularly high quality and suited to the dry Kenyan climate. SL28 & 34 produce a full-bodied cup with good acidity, often with notes of blackberry and blackcurrant. Kenya grows the vast majority of this prized coffee.
Caturra - A mutation of Bourbon discovered in Brazil in 1935, which was higher-yielding still. Very common throughout Latin America. Caturra can produce high-quality coffee, but even experienced coffee tasters probably wouldn't be able to distinguish a Caturra from a Typica in a blind tasting.
Catuai - A hybrid of Caturra and Mundo Novo (which is itself a natural hybrid of Bourbon and Typica). Catuai is high-yielding, and can produce good coffee, but, like Caturra, is not particularly distinctive. Grown in Brazil and Latin America.
Pacamara - A hybrid of Pacas, a descendent of Bourbon, and Red Maragogipe, a mutation of Typica. Developed in El Salvador in 1958, and still mainly grown there. Pacamara plants produce extremely large beans and often display a jasmine aroma.
Ethiopian heirloom varieties - Ethiopia is the birthplace of coffee, and most Ethiopian coffee is produced from native plants. The genetic diversity of Ethiopian coffee plants is far greater than the diversity of cultivated varieties, and Ethiopian coffee can display a huge range of flavors.
Gesha - A wild Ethiopian variety of coffee which was exported to Panama in the 1960s for its disease-resistance, but was found to be relatively low-yielding and therefore was not widely planted. In 2004, the variety was rediscovered when La Esmerelda, a farm in Panama, won the national Cup of Excellence competition with their Gesha coffee. Since then, it has become specialty coffee's most sought after coffee, at one point selling for $170 a pound—unroasted! Gesha is known for its intense floral aromatics, reminiscent of its Ethiopian heritage.
Sources:
http://www.atlascoffee.com/pacamara.pdf
http://wetmill.tumblr.com/page/2
http://www.coffeereview.com/article.cfm?ID=161
http://www.terroircoffee.com/content/view/260/
Thursday, December 27, 2012
Monday, December 24, 2012
San Diego Breweries
Over the past decade, San Diego has emerged as the leading beer city in America, possibly the world. With over 48 craft breweries in the county, mostly focused on beer geek styles like double IPAs, imperial stouts, and sour beers, it's certainly worth a visit. Before returning home for break, I spent some time with my Angry Monocle co-conspiritor, Jack, seeking out the finest ales San Diego had to offer. Here are some thoughts.
Day 1:
Breakwater Brewing Company, Oceanside – A bustling brewpup in downtown Oceanside. We were drawn in by the Biere du Jour, a raspberry-hibiscus mead blended with stout and aged in Brettanomyces-inhabited wine barrels. Strange, to say the least. Not much stout character left. I'm not a fan of hibiscus, so that was off-putting to me, but the main problem was the intensely dry, empty finish. Reminded me of something Dogfish Head might make. We also had a decent double IPA.
Pizza Port, Carlsbad – Raucous: family-style seating, with children to match. This was my second visit to a Pizza Port; I had previously been to their location in San Clemente. The pizza is quite good: I'm a fan of the Pizza Carlsbad, with pesto, mesquite grilled chicken, sun-dried tomatoes, artichoke hearts and feta. A good IPA is one of the few drinks that pairs well with artichoke. Pizza Port is known for their IPAs, so both of my visits I've ordered one. I don't remember the names, but they were both tap-only house beers, and both were underwhelming—lacking the intense aromatics I look for in a fresh IPA. However, I did also order a pint of Alpine's Duet IPA, which was hands down the best of the 11 IPAs I tasted that weekend. Super clean bitterness with pungent floral aromatics.
Lost Abbey, San Marcos – Located in one of the many industrial parks we visited, Lost Abbey is worth a visit just for its open-to-the-public barrel room. Unfortunately, there wasn't a single sour on tap, so we split a pint of Old Viscosity and moved on, after ogling the multitude of barrels with unconcealed envy.
Day 2:
Societe Brewing Company, San Diego – One of the nicer-looking tasting rooms we visited. I guess it should be, since Societe is only six months old. We had a few IPAs, which were all well-made and interesting, but none of which blew me away. I think my favorite of their beers was actually a Belgian pale ale called The Harlot. Definitely a brewery to watch, as they have a sour program going that should come to fruition in the next couple of years. Given the brewers' experience at Russian River and The Bruery, I'm excited to see what they turn out.
Toronado (Bar), San Diego – Hell of a bar. Had my first taste of Rodenbach Grand Cru (!). Also a couple more Alpine beers. Odin's Raven, an imperial stout, was flawless but uninspiring. Keene Idea, a double IPA with Nelson Sauvin hops, was incredibly pungent and unique, but I actually found the gooseberry hop aromatics in this beer to be off-putting (hints of onion). Food was ok. Burgers were generously thick—too thick, if you ask me—and the bottom bun was sopping wet by the time I was served. Also, a side of 'chips' meant potato chips, not french fries, which was a disappointment. Still, the astoundingly awesome tap list makes it hard for me to complain about this place.
Day 3:
Rough Draft Brewing Company, San Diego – We had some IPAs here. Hop Therapy, a double IPA, had a really nice melon note to it. Don't remember much else. The bartender wore bright red lipstick. There seemed to be a fair number of regulars.
Blind Lady Ale House & Automatic Brewing Company, San Diego – We tried to come here on Day 2, but it was closed for a private event involving Will Ferrell. We tried Automatic's Equal Rye & Justice, a rye pale ale dry hopped with Citra, which was pretty good. Looked like they had good food.
Green Flash – More taps than any of the other tasting rooms we'd been to. Some very interesting beers, such as Candela, a rye barleywine aged on cedar. Conclusion: don't age beer on cedar. Some of their IPAs were pretty good, but I still haven't found another Green Flash beer that comes close to their Double Stout.
Stone Brewing Company, Escondido – Classy restaurant. None of the Stone beers on tap looked terribly exciting. Had a bottle of Drie Fonteinen Oude Geuze, which was terribly exciting. Also had a glass of Stillwater's Cellar Door saison, which I didn't much care for. Something tasted off. Might've been the sage they added. The food was good, but not great, considering the classiness of the restaurant.
Part 2:
When I visited my uncle in San Clemente recently, we drove down to his friend Steven's place in Encinitas and brewed a rhubarb saison on his ($5,000) Sabco system. Since we started brewing at 6am, we were finished by mid-morning, and decided to make a couple more stops while we were in the area.
Ballast Point: An excellent selection of exclusive taps from their pilot system, including a few barrel-aged offerings, such as 2010 Three Sheets barleywine, aged in Syrah barrels. Well-made, but too oxidized for my tastes. Their brandy barrel-aged Navigator doppelbock, however, was the best doppelbock I've had. And, of course, Sculpin fresh from the brewery is about as good as it gets.
White Labs: This yeast lab hosts a tasting room where you can try the same beer fermented with several different yeasts. When we visited, they were featuring saison, hefeweizen, and robust porter. To be honest, I didn't think any of the saisons were very good. Two of the hefeweizens were quite good: the one fermented with WLP300 (the classic hefe strain) had typical banana aroma, with a dry wheat finish, while the one fermented with WLP380 (a different strain from Weihenstephan), had similar aromatics, but a cleaner, fruitier finish, with a bit more tartness. I was glad to find that the robust porter fermented with WLP007 (which I used for my porter) was the best of the four porters. WLP004 (Irish ale) was also decent, but sweeter and less aromatic. The porter with WLP011 (European ale) had some interesting esters, but did not compliment the roasted malts very well. The porter with WLP001 (California ale) was boring as heck.
Day 1:
Breakwater Brewing Company, Oceanside – A bustling brewpup in downtown Oceanside. We were drawn in by the Biere du Jour, a raspberry-hibiscus mead blended with stout and aged in Brettanomyces-inhabited wine barrels. Strange, to say the least. Not much stout character left. I'm not a fan of hibiscus, so that was off-putting to me, but the main problem was the intensely dry, empty finish. Reminded me of something Dogfish Head might make. We also had a decent double IPA.
Pizza Port, Carlsbad – Raucous: family-style seating, with children to match. This was my second visit to a Pizza Port; I had previously been to their location in San Clemente. The pizza is quite good: I'm a fan of the Pizza Carlsbad, with pesto, mesquite grilled chicken, sun-dried tomatoes, artichoke hearts and feta. A good IPA is one of the few drinks that pairs well with artichoke. Pizza Port is known for their IPAs, so both of my visits I've ordered one. I don't remember the names, but they were both tap-only house beers, and both were underwhelming—lacking the intense aromatics I look for in a fresh IPA. However, I did also order a pint of Alpine's Duet IPA, which was hands down the best of the 11 IPAs I tasted that weekend. Super clean bitterness with pungent floral aromatics.
Lost Abbey, San Marcos – Located in one of the many industrial parks we visited, Lost Abbey is worth a visit just for its open-to-the-public barrel room. Unfortunately, there wasn't a single sour on tap, so we split a pint of Old Viscosity and moved on, after ogling the multitude of barrels with unconcealed envy.
Day 2:
Societe Brewing Company, San Diego – One of the nicer-looking tasting rooms we visited. I guess it should be, since Societe is only six months old. We had a few IPAs, which were all well-made and interesting, but none of which blew me away. I think my favorite of their beers was actually a Belgian pale ale called The Harlot. Definitely a brewery to watch, as they have a sour program going that should come to fruition in the next couple of years. Given the brewers' experience at Russian River and The Bruery, I'm excited to see what they turn out.
Toronado (Bar), San Diego – Hell of a bar. Had my first taste of Rodenbach Grand Cru (!). Also a couple more Alpine beers. Odin's Raven, an imperial stout, was flawless but uninspiring. Keene Idea, a double IPA with Nelson Sauvin hops, was incredibly pungent and unique, but I actually found the gooseberry hop aromatics in this beer to be off-putting (hints of onion). Food was ok. Burgers were generously thick—too thick, if you ask me—and the bottom bun was sopping wet by the time I was served. Also, a side of 'chips' meant potato chips, not french fries, which was a disappointment. Still, the astoundingly awesome tap list makes it hard for me to complain about this place.
Day 3:
Rough Draft Brewing Company, San Diego – We had some IPAs here. Hop Therapy, a double IPA, had a really nice melon note to it. Don't remember much else. The bartender wore bright red lipstick. There seemed to be a fair number of regulars.
Blind Lady Ale House & Automatic Brewing Company, San Diego – We tried to come here on Day 2, but it was closed for a private event involving Will Ferrell. We tried Automatic's Equal Rye & Justice, a rye pale ale dry hopped with Citra, which was pretty good. Looked like they had good food.
Green Flash – More taps than any of the other tasting rooms we'd been to. Some very interesting beers, such as Candela, a rye barleywine aged on cedar. Conclusion: don't age beer on cedar. Some of their IPAs were pretty good, but I still haven't found another Green Flash beer that comes close to their Double Stout.
Stone Brewing Company, Escondido – Classy restaurant. None of the Stone beers on tap looked terribly exciting. Had a bottle of Drie Fonteinen Oude Geuze, which was terribly exciting. Also had a glass of Stillwater's Cellar Door saison, which I didn't much care for. Something tasted off. Might've been the sage they added. The food was good, but not great, considering the classiness of the restaurant.
Part 2:
When I visited my uncle in San Clemente recently, we drove down to his friend Steven's place in Encinitas and brewed a rhubarb saison on his ($5,000) Sabco system. Since we started brewing at 6am, we were finished by mid-morning, and decided to make a couple more stops while we were in the area.
Ballast Point: An excellent selection of exclusive taps from their pilot system, including a few barrel-aged offerings, such as 2010 Three Sheets barleywine, aged in Syrah barrels. Well-made, but too oxidized for my tastes. Their brandy barrel-aged Navigator doppelbock, however, was the best doppelbock I've had. And, of course, Sculpin fresh from the brewery is about as good as it gets.
White Labs: This yeast lab hosts a tasting room where you can try the same beer fermented with several different yeasts. When we visited, they were featuring saison, hefeweizen, and robust porter. To be honest, I didn't think any of the saisons were very good. Two of the hefeweizens were quite good: the one fermented with WLP300 (the classic hefe strain) had typical banana aroma, with a dry wheat finish, while the one fermented with WLP380 (a different strain from Weihenstephan), had similar aromatics, but a cleaner, fruitier finish, with a bit more tartness. I was glad to find that the robust porter fermented with WLP007 (which I used for my porter) was the best of the four porters. WLP004 (Irish ale) was also decent, but sweeter and less aromatic. The porter with WLP011 (European ale) had some interesting esters, but did not compliment the roasted malts very well. The porter with WLP001 (California ale) was boring as heck.
Sunday, December 23, 2012
Berliner Weisse (12/23/12)
This was my first attempt at a Berliner Weisse. For this batch I pitched lactobacillus at the same time as brewer's yeast, and let it ferment at 70F for several months. It never developed anywhere near the level of sourness that I wanted, so for subsequent batches I radically changed my approach to souring.
Vitals:
Yeast: 1/2 packet Nottingham, 2 packs of Lactobacillus delbruckii (Wyeast @ almost 6 months, White Labs @ 1 month but left 1 week unrefrigerated)
Starter: Wyeast lacto starter: 2 liters (1/2 DME, 1/2 cane sugar) for 5 days; no starter for White Labs lacto
Original Gravity (Calc): 1.034
Final Gravity (Measured): 1.002
ABV (Est): 4.1%
IBUs (Tinseth calcuation): 6
Strike temp: 165F
Mash in: 155F
End of mash: 149F
Mash length: 60 minutes
Mash thickness: 1.5 qt/lb
Mash efficiency: 63%
Pitching temp: 68F
1/3/13: Gravity is 1.004. Some mild esters in the aroma, but overall the beer is dominated by the sweetness of the doughy wheat malt. No bitterness to speak of. Some tartness, but less than I'd like. Added 3.75 lbs of thawed whole blackberries from Whole Foods.
2/13/13: Gravity at 1.002. Disappointing aroma and flavor.
2/22/13: Added 1 vial of Brett Brux.
3/1/13: Bottled to 2.5 volumes of CO2.
Vitals:
Yeast: 1/2 packet Nottingham, 2 packs of Lactobacillus delbruckii (Wyeast @ almost 6 months, White Labs @ 1 month but left 1 week unrefrigerated)
Starter: Wyeast lacto starter: 2 liters (1/2 DME, 1/2 cane sugar) for 5 days; no starter for White Labs lacto
Original Gravity (Calc): 1.034
Final Gravity (Measured): 1.002
ABV (Est): 4.1%
IBUs (Tinseth calcuation): 6
Strike temp: 165F
Mash in: 155F
End of mash: 149F
Mash length: 60 minutes
Mash thickness: 1.5 qt/lb
Mash efficiency: 63%
Pitching temp: 68F
| Malts Mashed | Amount | % | Max Pts. | |
| White Wheat | 2 | 27% | 40.00 | |
| 2 Row | 5.5 | 73% | 36.00 | |
| Hops/Additions | Amount | Time | AA% | |
| Spalt | 0.75 | 20 | 4.0% | |
1/3/13: Gravity is 1.004. Some mild esters in the aroma, but overall the beer is dominated by the sweetness of the doughy wheat malt. No bitterness to speak of. Some tartness, but less than I'd like. Added 3.75 lbs of thawed whole blackberries from Whole Foods.
2/13/13: Gravity at 1.002. Disappointing aroma and flavor.
2/22/13: Added 1 vial of Brett Brux.
3/1/13: Bottled to 2.5 volumes of CO2.
Saturday, December 1, 2012
Coffee Extraction
Coffee brewing advice is often hard to trust, due to much of the industry's lack of scientific knowledge, and the fact that most of the people giving the advice are trying to sell some fancy new brewing device. For exactly this reason, the most important coffee-related invention of the past few decades isn't a coffee brewer, grinder, or filter. It's a refractometer.
Both of these extremes are undesirable. While consumer preferences regarding coffee strength vary significantly, preferences regarding level of extraction are remarkably consistent. Coffee strength is expressed as the percentage of the brewed coffee that consists of dissolved coffee solids (% TDS). The Specialty Coffee Association of America recommends that brewed coffee consist of 1.15% - 1.35% TDS, while the Specialty Coffee Association of Europe recommends 1.2% - 1.5% TDS. These numbers are flexible; a ristretto shot of espresso can be upwards of 10% TDS and delicious.
Extraction yield is far less flexible. Extraction is expressed as the percentage of the ground coffee that is dissolved into the brewed coffee. The SCAA and SCAE recommend 18% - 22% extraction for both brewed coffee and espresso. This means that about one-fifth of the coffee in your brewer should end up in your cup, regardless of how strong you like your coffee.
Refractometers, as the name suggests, measure the refractive index of a material (i.e., the amount that light bends when passing through said material). If that material is a liquid, a refractometer can be used to measure how much stuff is dissolved in the liquid—the total dissolved solids (TDS)—by measuring the difference between the refractive index of the solvent (e.g., water) and the solution (e.g., brewed coffee). Of course, refractometers have been around since the 19th century, but it wasn't until 2008, when VST Technologies released a refractometer specifically designed for coffee, that specialty coffee shops started using them to measure coffee strength and extraction yields. (I'm sure the fact that VST released an iPhone app to go with the refractometer helped to encourage adoption.)
So why is this important? Don't we already know how to make coffee stronger or weaker? Just use more or less coffee! Well, yes, but there is a crucial distinction between strength and extraction. One might take a very small amount of coffee and boil it for an hour, or take a large amount of coffee and steep it in cold water for a few seconds. The resulting solutions might be the same strength, but would have very different levels of extraction. The boiled coffee would contain nearly all the soluble solids from the coffee grounds, while the coffee steeped for a few seconds would contain only a small fraction of those soluble solids.
Extraction yield is far less flexible. Extraction is expressed as the percentage of the ground coffee that is dissolved into the brewed coffee. The SCAA and SCAE recommend 18% - 22% extraction for both brewed coffee and espresso. This means that about one-fifth of the coffee in your brewer should end up in your cup, regardless of how strong you like your coffee.
Where did these numbers come from? The Coffee Brewing Institute (long since defunct) first studied consumer preferences for extraction levels in the 1950s, and their research has since been replicated by multiple organizations in several countries. The CBI originally came up with 17.5% - 21.2%, but more recent studies have settled on 18% - 22%. More information on these studies can be found in a post by Vince Fedele, head of VST. The point is, this number is based on empirical evidence regarding the preferences of the general public.
Overextraction results in intensely bitter coffee, while underextracted coffee is usually sour and lacking in complexity. The distinction between sourness and acidity is, as far as I can tell, unique to coffee. Acidity is generally a desirable characteristic in coffee; sourness refers to an acidic coffee that lacks the sweetness to balance its acidity. Since the caramelized sugars that give coffee its sweetness are less soluble than acids (the main acids in coffee are citric and malic), underextracted coffee is often sour in this sense.
Overextraction results in intensely bitter coffee, while underextracted coffee is usually sour and lacking in complexity. The distinction between sourness and acidity is, as far as I can tell, unique to coffee. Acidity is generally a desirable characteristic in coffee; sourness refers to an acidic coffee that lacks the sweetness to balance its acidity. Since the caramelized sugars that give coffee its sweetness are less soluble than acids (the main acids in coffee are citric and malic), underextracted coffee is often sour in this sense.
The ultimate goal of any coffee brewer, therefore, is to achieve extraction yields of 18% - 22%. Extraction yield is affected by a number of variables, including: water temperature, grind size, brew time, agitation, coffee/water ratio, water profile, and coffee density and roast level. The problem is that the only way to measure extraction directly is to dry the spent grounds in an oven and weigh them, a process that takes hours and careful attention to detail. Because of the difficulty of measuring extraction, for decades the only people doing so were at large research institutes. However, if one could accurately measure the strength of the brewed coffee and the mass of the ground coffee and brew water, it would be possible to calculate extraction yield by the following formula: Extraction[%] = BrewedCoffee[g] * TDS[%] / CoffeeGrounds[g]. The mass of coffee grounds and brewed coffee can be easily measured with a scale, but measuring TDS is more difficult.
An affordable option is to buy a cheap TDS meter, such as those used to measure water quality. I bought one of these, but found that my readings varied wildly. The refinement provided by VST's coffee refractometer was a major improvement. Unfortunately, the device costs $400, which is more than I could justify to myself; but for a café that has already spent thousands upon thousands of dollars on espresso machines and grinders, spending $400 to ensure consistent quality is a small price.
The emergence of an objective measure of quality is powerful. 18%-22% extraction does not guarantee a great cup of coffee; the coffee itself still has to be good. But extraction yield is an objective evaluation of the brewing method, allowing for further empirical research into coffee brewing. Two significant results were presented at this year's Nordic Barista Cup. The first was a study by David Walsh reconfirming the validity of the 18%-22% extraction preference, while also suggesting a secondary preference for extractions at 12.5%-14.5%.
The second was an analysis by Vince Fedele of the liquid retained by the coffee grounds after brewing. The standard equation for calculating extraction yield from brew strength disregards any coffee extracted by the liquid retained by the spent coffee grounds. This assumption turns out to be roughly true of percolation brewing methods (drip, espresso), but not of infusion methods (e.g., French press, syphon/vacuum, Aeropress). When brewing by percolation, the liquid retained by the coffee has only been in contact with the coffee for a short time, and hence has extracted very little coffee. When brewing by infusion, on the other hand, the retained liquid has been in contact with the coffee for the entire brewing process. Therefore, the liquid retained by an infusion brewer has a significant quantity of coffee solids in solution; the retained liquid is coffee of essentially the same strength as the cup you just brewed. The standard extraction formula doesn't take this extra extraction into account. Practically, this means that to brew coffee to the same strength and extraction by infusion requires ~10% more ground coffee, to account for the brewed coffee that is retained by the grounds.
In addition to allowing cafés and consumers to improve their brewing practices, fast and easy measurement of extraction is a valuable tool for engineers developing coffee equipment. For example, soon after developing the VST refractometer, Vince Fedele used his invention to identify a major weakness in commercial espresso machines—the portafilter basket—and develop an improvement.
The second was an analysis by Vince Fedele of the liquid retained by the coffee grounds after brewing. The standard equation for calculating extraction yield from brew strength disregards any coffee extracted by the liquid retained by the spent coffee grounds. This assumption turns out to be roughly true of percolation brewing methods (drip, espresso), but not of infusion methods (e.g., French press, syphon/vacuum, Aeropress). When brewing by percolation, the liquid retained by the coffee has only been in contact with the coffee for a short time, and hence has extracted very little coffee. When brewing by infusion, on the other hand, the retained liquid has been in contact with the coffee for the entire brewing process. Therefore, the liquid retained by an infusion brewer has a significant quantity of coffee solids in solution; the retained liquid is coffee of essentially the same strength as the cup you just brewed. The standard extraction formula doesn't take this extra extraction into account. Practically, this means that to brew coffee to the same strength and extraction by infusion requires ~10% more ground coffee, to account for the brewed coffee that is retained by the grounds.
In addition to allowing cafés and consumers to improve their brewing practices, fast and easy measurement of extraction is a valuable tool for engineers developing coffee equipment. For example, soon after developing the VST refractometer, Vince Fedele used his invention to identify a major weakness in commercial espresso machines—the portafilter basket—and develop an improvement.
But more than anything else, I appreciate the development of the VST refractometer, and the renewed focus on extraction it brought with it, for the simplicity it provides. Though extraction is a complex concept, it is a single, measurable number which tracks quality of brewing methods.
There's one major caveat to these extraction numbers, which is that they're based on what our grinders actually produce. Even the best burr grinders on the market produce a significant quantity of grinds that are finer than desired. These fines extract more quickly than the rest of the coffee, which puts a limit on how high we can push our extraction yield without overextracting. If you have a low-quality grinder (e.g., a blade grinder), even an 18% extraction is going to taste over extracted, due to the wide variation in grind size. Experiments with sifting ground coffee, which removes the fines, suggest that a perfectly even grind would allow extraction up to 23% or 24%. (Matt Perger won this year's World Brewer's Cup with sifted coffee at 23% extraction.) But sifting is impractical in most settings, so until the next grinder revolution, we're stuck with a 22% ceiling.
There's one major caveat to these extraction numbers, which is that they're based on what our grinders actually produce. Even the best burr grinders on the market produce a significant quantity of grinds that are finer than desired. These fines extract more quickly than the rest of the coffee, which puts a limit on how high we can push our extraction yield without overextracting. If you have a low-quality grinder (e.g., a blade grinder), even an 18% extraction is going to taste over extracted, due to the wide variation in grind size. Experiments with sifting ground coffee, which removes the fines, suggest that a perfectly even grind would allow extraction up to 23% or 24%. (Matt Perger won this year's World Brewer's Cup with sifted coffee at 23% extraction.) But sifting is impractical in most settings, so until the next grinder revolution, we're stuck with a 22% ceiling.