This set moves into the technical maintenance of equipment, the biology of the cherry, and the sensory experience of “mouthfeel.”
Article 161: The Anatomy of a Coffee Cherry
(Category: Coffee Education | Word Count: ~320)
To understand processing, we must understand what we are removing. A coffee cherry is made of several distinct layers:
- Exocarp (Skin): The outer, waxy green skin that turns red (or yellow) when ripe.
- Mesocarp (Mucilage): The “flesh” of the fruit. It is sticky, sugary, and pectin-rich. This layer is what drives fermentation.
- Parenchyma (Pectin Layer): A thin, slimy layer between the mucilage and the parchment.
- Endocarp (Parchment): The tough, paper-like shell that protects the bean inside.
- Spermoderm (Silver Skin): A thin, papery film that clings to the bean, even after milling.
- Endosperm (The Bean): The actual seed we roast and grind.
When we say coffee is “Washed,” we are removing layers 1, 2, and 3 before drying. When it is “Natural,” we dry the bean with all these layers intact. Each layer removed or kept changes the final flavor profile of your cup.
Article 162: Cleaning the Grinder: The “Burr” Reality
(Category: Barista Skills | Word Count: ~230)
Many baristas remember to clean their espresso machine but forget the grinder. Over time, coffee oils stick to the steel burrs and the exit chute. These oils turn rancid, adding a “fishy” or “stale” taste to your fresh coffee.
The Maintenance Steps: - The Brush: Every evening, close the hopper and grind out the remaining beans. Use a stiff brush to clean the “teeth” of the burrs.
- The Vacuum: Use a small vacuum to suck out the old grounds from the chute.
- Cleaning Tablets: Products like Grindz (food-safe tablets) can be run through the grinder once a week. They absorb the oils from the burrs without you having to take the whole machine apart.
Clean burrs produce a more uniform grind, which leads to better extraction and a much cleaner flavor in the cup.
Article 163: Understanding “Tannins” in Coffee
(Category: Coffee Science | Word Count: ~210)
Tannins are polyphenols found in coffee (and tea and wine). They are responsible for the astringency or “dryness” you sometimes feel on your tongue after a sip.
In a well-brewed Kenyan coffee, tannins are present in very low amounts, providing just enough “structure” to the drink. However, if you over-extract your coffee (by using water that is too hot or grinding too fine), you pull out an excessive amount of tannins. This causes the proteins in your saliva to clump together, leaving your mouth feeling dry, like you’ve been sucking on a tea bag. If your coffee leaves you reaching for a glass of water, you’ve likely over-extracted the tannins.
Article 164: The “Flat Bottom” vs. “Conical” Dripper
(Category: Brewing Methods | Word Count: ~290)
The shape of your brewer changes the way water moves through the coffee bed. - Conical (V60/Chemex): The water converges at a single point. This creates a deeper bed of coffee, which leads to higher “clarity” and highlights acidity. It requires a more precise pouring technique to avoid “channelling.”
- Flat Bottom (Kalita Wave/Fellow Stagg): The water moves straight down through a flat bed. This creates a more uniform extraction and usually results in a heavier body and more “sweetness” or “chocolate” notes. It is much more “forgiving” for beginners.
At Kenya Coffee School, we often prefer conical brewers for Kenyan beans to highlight their famous “sparkling” acidity, but we use flat-bottom brewers for lower-acid beans to maximize their creamy mouthfeel.
Article 165: Why “Pressure Profiling” is the New Frontier
(Category: Barista Skills | Word Count: ~250)
Standard espresso machines pump water at a constant 9\text{ bars} of pressure. Advanced machines allow for Pressure Profiling, where the barista can change the pressure during the shot.
The Benefits: - Pre-infusion: Starting at 2\text{ bars} for 5 seconds “wets” the puck, reducing the chance of channelling.
- The Ramp-Up: Moving to 9\text{ bars} for the main extraction.
- The Taper: Reducing to 5\text{ bars} at the end of the shot. This prevents the “blonding” phase from extracting bitter tannins, resulting in a much sweeter, smoother finish.
Pressure profiling allows a barista to “rescue” a light-roasted coffee that might otherwise taste too sour, or a dark-roasted coffee that might otherwise be too bitter.
Article 166: The “Coffee Taster’s Flavor Wheel”
(Category: Sensory Skills | Word Count: ~310)
The Flavor Wheel is a universal tool used by baristas and cuppers to describe coffee. It moves from the center (General) to the outside (Specific).
How to use it: - Start in the center: Do you taste “Fruit,” “Floral,” or “Roasted”?
- Move one layer out: If it’s “Fruit,” is it “Berry,” “Dried Fruit,” or “Citrus”?
- Find the specific: If it’s “Citrus,” is it “Grapefruit,” “Orange,” or “Lemon”?
In Kenya, we spend a lot of time in the Fruit/Berry section. When we say a coffee has “notes of blackcurrant,” we aren’t saying someone added fruit to the bag; we are saying the chemical compounds in the coffee trigger the same receptors in our brain that actual blackcurrants do. The Wheel helps us communicate that experience to the customer.
Article 167: What is a “Flat White” Really?
(Category: Barista Skills | Word Count: ~240)
Originating from Australia and New Zealand, the Flat White has taken the world by storm. But how does it differ from a Latte or a Cappuccino? - Latte: 8\text{ oz} – 12\text{ oz} cup, 1\text{ cm} of foam, mild espresso taste.
- Cappuccino: 6\text{ oz} cup, 1.5\text{ cm} of “stiff” foam, balanced taste.
- Flat White: 5\text{ oz} – 6\text{ oz} cup, very thin layer (0.5\text{ cm}) of high-density microfoam.
The Flat White is designed to be a “coffee-forward” drink. Because there is less milk and very little air in the foam, the espresso flavor is much more intense. It is the perfect milk drink for someone who actually wants to taste the specific character of a specialty Kenyan bean.
Article 168: The “Vibration” vs. “Rotary” Pump
(Category: Coffee Business | Word Count: ~220)
When buying an espresso machine, you will see two types of pumps: - Vibration Pump: Small, inexpensive, and loud. Found in most home machines. It takes a few seconds to build up to full pressure.
- Rotary Pump: Large, expensive, and nearly silent. Found in all commercial café machines. It provides instant, rock-solid pressure and can be “plumbed in” directly to your water line.
For a professional café, a Rotary Pump is essential. It is built to pull hundreds of shots a day without overheating, whereas a vibration pump will struggle to maintain consistency in a busy environment.
Article 169: Understanding “Mouthfeel” (Body)
(Category: Sensory Skills | Word Count: ~210)
Body is not a “taste”; it is a tactile sensation. It is the weight and texture of the coffee on your tongue.
Common Descriptions: - Watery/Thin: Like tea.
- Silky/Creamy: Like whole milk.
- Syrupy/Heavy: Like maple syrup or honey.
Kenyan coffees are unique because they often have a “Juicy” mouthfeel. This means they have the brightness of fruit juice but with enough “weight” to feel satisfying. Body is created by the oils and undissolved solids in the coffee. A French Press will always have more “body” than a V60 because it doesn’t have a paper filter to catch those oils.
Article 170: Why we “Purge” the Grinder between Changes
(Category: Barista Skills | Word Count: ~180)
Whenever you adjust your grinder from “coarse” to “fine,” there is always about 5\text{g} – 10\text{g} of coffee “retained” inside the machine.
If you don’t “purge” (grind out and throw away a small amount), your next shot will be a mixture of two different grind sizes. This makes “dialing in” impossible because you aren’t seeing the true result of your adjustment. Waste is a necessary part of precision—always purge before you pull your “test” shot!