Here is the third batch of 10 articles (Articles 21 through 30). Focusing on technical barista skills, coffee science, and Kenyan-specific industry knowledge.
Article 21: Understanding Coffee “Channelling” and How to Fix It
(Category: Barista Skills | Word Count: ~320)
In espresso brewing, water is lazy; it will always seek the path of least resistance. Channelling occurs when high-pressure water finds a small crack or a less dense area in your coffee puck and blasts through it, rather than flowing evenly through the entire bed.
The Result: The coffee in the channel is over-extracted (bitter and harsh), while the rest of the puck is under-extracted (sour and thin). The final shot will taste both sour and bitter simultaneously.
How to Identify Channelling:
- If using a bottomless (naked) portafilter, you will see “spurts” or multiple streams that don’t merge into one.
- The espresso flow will suddenly speed up and turn blond very quickly.
- Looking at the spent puck, you might see small pinholes or cracks.
How to Fix It: - Distribution is Key: Ensure the grounds are level in the basket before tamping. Use your finger or a distribution tool to eliminate clumps.
- Level Tamping: If your tamp is tilted, water will rush to the lower side. Keep your tamper perfectly horizontal.
- Check Your Basket: Ensure the basket is bone-dry before adding coffee. Moisture on the walls causes the coffee to “pull away,” creating a channel around the edges (edge channelling).
Mastering distribution is the most effective way to eliminate channelling and ensure a balanced shot.
Article 22: The Impact of Altitude on Coffee Flavor
(Category: Coffee Bean Knowledge | Word Count: ~350)
In the world of specialty coffee, altitude is often treated as a badge of quality. You will frequently see labels like “SHG” (Strictly High Grown) or “SHB” (Strictly Hard Bean). But why does height matter?
Slower Maturation:
At higher altitudes (typically above 1,500\text{ meters}), the climate is cooler. This causes the coffee cherry to ripen much more slowly than it would at sea level. This extended maturation period allows the plant more time to develop complex sugars and organic acids within the bean.
Bean Density:
High-altitude coffee is physically harder and denser. These “Hard Beans” can withstand higher temperatures during roasting, allowing roasters to apply more heat and unlock more complex flavor profiles without burning the exterior of the bean.
Flavor Characteristics: - High Altitude (1,200\text{m} – 2,000\text{m}+): Expect high acidity, floral notes, and complex fruit flavors (berries, citrus). This is where most Kenyan SL28 and SL34 varietals thrive.
- Low Altitude (Below 1,000\text{m}): These beans mature quickly. They tend to have lower acidity, more earthy/nutty flavors, and less complexity. They are often less dense and require a gentler roasting profile.
When you buy Kenyan coffee, you are often buying some of the highest-grown coffee in the world, which is why it is famous for its “bright” and “winy” acidity.
Article 23: The 4:6 Method for V60 Perfection
(Category: Brewing Methods | Word Count: ~380)
Developed by World Brewers Cup Champion Tetsu Kasuya, the 4:6 Method is a revolutionary way to think about pour-over coffee. It suggests that you can control the flavor of your coffee simply by adjusting the volume of your pours.
The Concept:
The total water volume is divided into two parts: 40\% and 60\%. - The First 40\%: Controls the balance between Acidity and Sweetness.
- The Remaining 60\%: Controls the Strength (TDS/Concentration).
How to Do It:
Let’s use 20\text{g} of coffee and 300\text{g} of water. Your total water is 300\text{g}. - Step 1 (Acidity vs. Sweetness): Divide the first 120\text{g} (40\%) into two pours.
- If you want more acidity, make the first pour smaller (e.g., 50\text{g} then 70\text{g}).
- If you want more sweetness, make the first pour larger (e.g., 70\text{g} then 50\text{g}).
- Step 2 (Strength): Divide the remaining 180\text{g} (60\%) into equal pours.
- For a lighter coffee, make fewer pours (e.g., one 180\text{g} pour).
- For a stronger coffee, divide it into more pours (e.g., three 60\text{g} pours).
The Grind:
This method requires a very coarse grind (like Kosher salt). Because you are pouring multiple times, the water spends more time in contact with the coffee. A coarse grind prevents the brew from becoming over-extracted and bitter.
The 4:6 method turns brewing into a mathematical formula, allowing you to “dial in” the exact flavor profile you prefer.
Article 24: Degassing: Why You Shouldn’t Brew “Freshly” Roasted Coffee
(Category: Roasting/Coffee Science | Word Count: ~240)
It is a common misconception that coffee is at its best the second it comes out of the roaster. In reality, coffee needs to “rest.”
During the roasting process, carbon dioxide (\text{CO}_2) builds up inside the bean. For the first 24\text{ to }48\text{ hours} after roasting, the bean is rapidly releasing this gas—a process called degassing.
Why Brewing Too Early is Bad:
If you brew coffee that is only a few hours old, the escaping \text{CO}_2 acts as a barrier. It pushes the water away from the grounds, preventing proper extraction. - In Espresso: It creates an unstable, bubbly crema and uneven pressure, making the shot taste sour and “metallic.”
- In Filter: It causes an aggressive bloom that can lead to uneven saturation.
The Sweet Spot:
Most specialty coffees reach their peak flavor between 5\text{ and }14\text{ days} after roasting. This allows enough gas to escape so that water can easily penetrate the bean, but keeps the volatile aromatic oils fresh. Always check the “Roast Date” on your bag, not the “Expiry Date.”
Article 25: Cold Brew vs. Iced Coffee: What’s the Difference?
(Category: Brewing Methods | Word Count: ~280)
Many people use the terms interchangeably, but Cold Brew and Iced Coffee are entirely different brewing processes that yield very different flavor profiles.
Iced Coffee: - Process: Coffee is brewed hot (using a V60, Chemex, or drip machine) and then cooled down or poured over ice.
- Flavor: Because it is brewed with hot water, it retains the acidity and bright floral notes of the bean. However, it can become bitter if not brewed slightly stronger to account for ice dilution (a method called “Flash Chilling”).
- Best For: High-quality African beans where you want to taste the “zing” and fruitiness.
Cold Brew: - Process: Coffee grounds are steeped in room temperature or cold water for a long period, typically 12\text{ to }24\text{ hours}.
- Flavor: Cold water does not extract the same acids and oils that hot water does. The result is a coffee that is 60\% – 70\% less acidic. It is incredibly smooth, naturally sweet, and heavy-bodied, with notes of chocolate and molasses.
- Best For: People with sensitive stomachs or those who enjoy a rich, creamy, and low-acid caffeine kick.
Whether you want the “brightness” of iced coffee or the “smoothness” of cold brew, both are excellent ways to enjoy coffee during Kenya’s warmer months.
Article 26: The Anatomy of a Coffee Cherry
(Category: Coffee Education | Word Count: ~220)
To understand coffee, you must first understand the fruit it comes from. The “bean” we roast is actually the seed of a fruit called a coffee cherry. - Outer Skin (Exocarp): The thin, green skin that turns red (or yellow/orange) when ripe.
- Pulp (Mesocarp): The fruit flesh. In “Natural” processing, this stays on the bean while drying; in “Washed” processing, it is removed immediately.
- Mucilage (Pectin Layer): A sticky, sugary layer beneath the pulp. This layer is responsible for much of the sweetness and body in the final cup.
- Parchment (Endocarp): A tough, paper-like hull that protects the seed. Coffee is often stored in its parchment (called “Parchment Coffee”) to keep it fresh before export.
- Silver Skin (Spermoderm): A thin, papery skin that covers the bean. This becomes the “chaff” that flies off during the roasting process.
- The Bean (Endosperm): The actual seed. Most cherries contain two seeds facing each other. If there is only one round seed, it is called a Peaberry.
Understanding these layers helps baristas appreciate the processing and milling steps required before the coffee ever reaches the café.
Article 27: Introduction to the Aeropress
(Category: Brewing Methods | Word Count: ~310)
Invented by the creator of the Aerobie frisbee, the Aeropress is a cult favorite among baristas due to its portability, durability, and extreme versatility. It combines three brewing styles: Immersion, Pressure, and Paper Filtration.
Why it’s Unique:
Unlike a V60 (gravity) or a French Press (immersion), the Aeropress allows you to experiment with almost every variable. You can change the grind size, temperature, and steep time to create anything from a concentrated, espresso-like shot to a clean, light filter cup.
The “Inverted Method” vs. “Standard Method”: - Standard: You place the Aeropress on the mug, add coffee and water, and press. Some water may drip through before you start pressing.
- Inverted: You flip the Aeropress upside down. This turns it into a full-immersion brewer (like a French Press). Once the steep time is up, you screw on the cap and flip it onto your mug to press. This gives you total control over the brew time with zero “leakage.”
Basic Recipe: - Ratio: 15\text{g} coffee to 250\text{ml} water.
- Grind: Medium-fine (like table salt).
- Process: Add water to the coffee, stir, wait 2\text{ minutes}, and press gently for 30\text{ seconds}.
The Aeropress is the perfect entry point for anyone starting their home brewing journey because it is almost impossible to break and very difficult to mess up!
Article 28: What is Specialty Coffee? (Beyond the Marketing)
(Category: Coffee Education | Word Count: ~330)
The term “Specialty Coffee” is often used in marketing, but in the industry, it has a very specific, technical definition. It is not just “good coffee”—it is coffee that has been verified at every stage of the supply chain.
The 80-Point Rule:
Coffee quality is graded on a 100-point scale by certified tasters known as Q-Graders. To be classified as “Specialty,” a coffee must score 80 points or higher. Coffee scoring below this is considered “Commodity” or “Commercial” grade.
The Requirements: - Zero Primary Defects: A 300\text{g} sample of green beans must have no “primary” defects (like black beans, sour beans, or stones).
- Traceability: Specialty coffee must be traceable to a specific farm, washing station, or lot. It is not a generic “Blend of East Africa.”
- Sensory Excellence: In the cup, it must exhibit distinct positive attributes in acidity, body, aroma, and flavor. It should be free of “taints” like mold or chemical tastes.
Why It Matters:
Specialty coffee focuses on quality over quantity. Because it is harder to produce, roasters pay farmers a significant premium above the market price. When you choose a specialty café like those supported by Kenya Coffee School, you aren’t just buying a better-tasting drink; you are supporting a system that rewards farmers for excellence rather than just volume.
Article 29: Cleaning Your Grinder: The “Purge” and the “Deep Clean”
(Category: Barista Skills | Word Count: ~260)
Even if you buy the most expensive coffee in the world, your brew will taste bad if your grinder is dirty. Coffee contains oils that stick to the metal burrs. Over time, these oils oxidize and turn rancid, adding a “fishy” or “stale” taste to your fresh coffee.
The Daily Purge:
Every morning, before you make your first coffee, “purge” your grinder. Grind about 10\text{g} – 20\text{g} of coffee and throw it away. This removes the “stale” grounds that were sitting between the burrs overnight.
The Weekly Deep Clean: - Grinder Cleaning Pellets: Use products like Urnex Grindz. These are food-safe tablets that you “grind” just like coffee. They absorb the oils and knock loose the stuck particles without you having to take the machine apart.
- Vacuuming: Use a vacuum hose to suck out the remaining dust from the chute and the hopper.
- The Hopper: Wipe the bean hopper with a dry cloth. Never use soap or water unless you dry it perfectly—moisture is the enemy of your grinder’s motor and burrs.
A clean grinder ensures that the only thing you taste in your cup is the coffee you just bought.
Article 30: The Role of the Kenya Coffee Board
(Category: Coffee Export/Business | Word Count: ~300)
The Kenyan coffee industry is one of the most regulated in the world, which is a major reason for its consistently high quality. Central to this regulation is the Coffee Board of Kenya (now part of the Agriculture and Food Authority – AFA).
What They Do: - Licensing: They issue licenses to growers, pulping stations, millers, and marketing agents. This ensures that every player in the chain meets specific hygiene and quality standards.
- The Auction System: Most Kenyan coffee is sold through the Nairobi Coffee Exchange (NCE). The Board oversees this transparent auction system, where samples are cupped by dozens of international buyers who bid on the best lots.
- Quality Control: They provide the official grading (AA, AB, C, etc.) that informs the world of the bean size and quality of each lot.
- Research and Development: They work alongside the Coffee Research Institute (CRI) to develop disease-resistant varietals like Ruiru 11 and Batian.
For students at the Kenya Coffee School, understanding the role of the Board is essential for navigating the legalities of the local industry, whether you want to open a café or start an export business. This regulatory framework protects the “Kenya Coffee” brand on the global stage.
I have now provided 30 articles. Should I continue with the next batch of 10? (I have 220 more to go!)