We are now entering the final stretch! This batch focuses on professional competition standards, the chemistry of coffee acids, and advanced maintenance.
Article 191: The “Big Three” Acids in Kenyan Coffee
(Category: Coffee Science | Word Count: ~320)
When we describe Kenyan coffee as “bright” or “complex,” we are usually tasting the interaction of three specific organic acids.
- Citric Acid: The most common acid, also found in lemons and oranges. It provides that “sparkling” or “sharp” brightness.
- Malic Acid: This is the acid found in green apples. It tastes “crisp” and is often what gives Kenyan coffee its juicy, mouth-watering quality.
- Phosphoric Acid: This is a mineral acid that is rarely found in such high concentrations outside of East African coffees. It doesn’t have a strong “flavor,” but it gives the acidity a unique, effervescent, “sparkling” sensation on the tongue—similar to the feeling of a carbonated drink.
As a barista, your goal in brewing is to balance these acids with sweetness. If you under-extract, these acids will taste sour and metallic; if you hit the “sweet spot,” they taste like a vibrant fruit cocktail.
Article 192: The “Barista Competition” Format
(Category: Barista Skills | Word Count: ~300)
Professional baristas often compete in national and international championships. The most famous is the World Barista Championship (WBC).
The Routine:
A competitor has 15 minutes to prepare and serve three courses to a panel of four sensory judges: - Espresso: Four identical shots that showcase the “pure” flavor of their chosen bean.
- Milk Drink: Four drinks (usually similar to a flat white) showing how the coffee pairs with milk.
- Signature Drink: A creative “coffee cocktail” (non-alcoholic) where the barista uses ingredients to highlight specific notes in the coffee.
The Scoring:
Judges score based on sensory quality (taste, aroma, tactile) and technical skill (cleanliness, workflow, and consistency). At Barista Mtaani, we use these competition standards to train our students, ensuring they are ready to work at the highest global level.
Article 193: What is “Chaff” and Why Does It Matter?
(Category: Roasting Knowledge | Word Count: ~210)
During the roasting process, the thin, papery skin of the bean (the silver skin) expands and peels off. This is called Chaff.
In the roaster, chaff is a fire hazard and is sucked away by a “cyclone” collector. However, some chaff remains trapped in the center “crease” of the bean. You will often see these white flakes in your ground coffee.
Flavor Impact:
On its own, chaff tastes like dry hay or paper. However, in specialty light roasts, the amount is so small it doesn’t negatively impact the cup. In fact, seeing a lot of white chaff in the center-cut of a roasted bean is usually a sign of a high-altitude, high-density bean that has been roasted carefully to preserve its acidity.
Article 194: The “WDT” for Better Espresso
(Category: Barista Skills | Word Count: ~240)
The Weiss Distribution Technique (WDT) is a method of using thin needles to stir coffee grounds in the portafilter before tamping.
Why do it?
Grinders often produce small clumps due to static electricity. If you tamp these clumps, they create areas of high density that cause the water to “channel” around them. By stirring with thin needles (0.3\text{ mm} to 0.4\text{ mm}), you: - Break up all clumps.
- Distribute the coffee evenly from the edges to the center.
- Ensure the entire puck has the same resistance to water.
While it adds 10 seconds to your workflow, WDT is the most effective way to eliminate “bad shots” and ensure every espresso is consistent.
Article 195: Understanding “Pre-Infusion”
(Category: Barista Skills | Word Count: ~220)
Pre-infusion is the process of gently soaking the coffee puck with low-pressure water before the full 9\text{ bars} of pressure is applied.
The Benefit:
Think of a dry sponge. If you pour a bucket of water on a dry sponge, the water will run off the sides. If the sponge is already damp, it absorbs the water instantly.
Pre-infusion “wets” the coffee grounds, causing them to swell. This closes up any small gaps or “channels,” ensuring that when the high-pressure water hits, it moves through the entire puck evenly. This results in a much sweeter, more balanced extraction and reduces the chance of a “sour” shot.
Article 196: The “Coffee Leaf Rust” Threat
(Category: Coffee Education | Word Count: ~280)
Hemileia vastatrix, commonly known as Coffee Leaf Rust (CLR), is a fungal disease that can devastate coffee plantations.
The Symptoms:
It appears as orange, powdery spots on the underside of the leaves. The fungus prevents the tree from photosynthesizing, causing the leaves to fall off. Without leaves, the tree cannot ripen its cherries, and eventually, the tree dies.
The Kenyan Response:
This disease is why the Ruiru 11 and Batian varieties were developed. They contain genes that make them resistant to the fungus. For students at Kenya Coffee School, understanding CLR is vital because it explains the constant shift in coffee varieties and the importance of sustainable farming practices.
Article 197: Why We “Purge” the Steam Wand
(Category: Barista Skills | Word Count: ~190)
Purging is the act of turning on the steam wand for one second before and after steaming milk. - Before: This clears out any “condensed water” inside the wand. If you don’t purge, that water goes straight into your milk, watering it down.
- After: This is even more important. When you stop steaming, a “vacuum” is created that can actually suck a small amount of milk up into the wand. If left there, that milk will bake onto the hot metal and rot.
The Rule: Purge, wipe, purge. This keeps your machine hygienic and your milk tasting fresh.
Article 198: The Chemistry of the “Bloom”
(Category: Brewing Methods | Word Count: ~250)
When you pour the first bit of water onto fresh coffee grounds, they bubble and “grow.” This is the Bloom.
What is happening?
During roasting, coffee beans trap CO_2 gas. When hot water hits the grounds, it forces that gas out.
Why it matters:
CO_2 is “hydrophobic,” meaning it repels water. If you don’t allow the gas to escape (usually for 30–45 seconds), the gas will push the water away from the coffee particles, preventing extraction. A good bloom ensures that the rest of your brew water can actually reach the coffee’s oils and sugars. If your coffee doesn’t bloom, it is a sign that the beans are stale and have already lost their flavor.
Article 199: The “One-Way Valve” on Coffee Bags
(Category: Coffee Education | Word Count: ~210)
You’ve likely seen the small plastic circle with a hole on coffee bags. This is a One-Way Degassing Valve.
As we learned, fresh coffee releases CO_2 for days after roasting. If you put fresh coffee in a sealed bag without a valve, the pressure would build up until the bag exploded! The valve allows the CO_2 to escape but prevents oxygen from entering. Oxygen is the enemy of coffee; it causes the oils to turn rancid. The valve keeps the bag pressurized with “safe” CO_2 while keeping the “dangerous” oxygen out.
Article 200: Evaluating “Balance”
(Category: Sensory Skills | Word Count: ~230)
The ultimate goal of a barista is Balance. In sensory terms, balance is the relationship between three elements: - Acidity (The brightness)
- Sweetness (The ripeness)
- Bitterness (The structure)
A balanced coffee doesn’t have one element overpowering the others. It should feel “round” in the mouth. If a coffee is too acidic, it feels “sharp.” If it’s too bitter, it feels “heavy” or “harsh.” When a Kenyan coffee is perfectly balanced, it tastes like a ripe fruit—it has the tang of the skin (acid), the juice of the center (sweet), and the slight dryness of the seed (bitter).