This batch dives into the chemistry of milk, advanced extraction theory, and the specific history of Kenyan coffee varietals.
Article 101: The Chemistry of Milk: Why Fat Matters
(Category: Barista Skills | Word Count: ~280)
For a barista, milk is not just a liquid; it is a complex biological emulsion. When we steam milk for a latte or cappuccino, the fat content plays a crucial role in both the texture and the flavor.
The Role of Lipids:
Milk fats (lipids) are responsible for the “creamy” mouthfeel of a latte. More importantly, they act as flavor carriers. However, fat is also a foam suppressor. This is why whole milk (3.5\% fat) creates a denser, more velvety microfoam than skim milk, which creates a “stiffer,” drier foam.
Temperature and Fat:
As you heat milk, the fats melt and coat the air bubbles you are introducing. If you overheat the milk (above 70^\circ\text{C}), these fats can break down, causing the foam to collapse and the milk to lose its natural sweetness. The “sweet spot” for milk is 60^\circ\text{C} to 65^\circ\text{C}, where the lactose (sugar) is most perceptible and the fats provide a stable, silky texture.
Article 102: Understanding “Ruiru 11”
(Category: Coffee Bean Knowledge | Word Count: ~320)
While SL28 and SL34 are the “kings” of flavor in Kenya, Ruiru 11 is the “survivor.” Developed in the 1980s at the Coffee Research Station in Ruiru, this variety was a direct response to the devastating Coffee Berry Disease (CBD) and Leaf Rust outbreaks.
The Genetic Mix:
Ruiru 11 is a “composite” variety. It was bred using a complex pedigree that includes:
- Ruminant Sudan: For CBD resistance.
- Hibrido de Timor: For Leaf Rust resistance.
- SL28 & SL34: To try and maintain that classic Kenyan flavor.
The Profile:
Ruiru 11 is a compact tree, meaning farmers can plant more trees per acre. While purists often argue that it lacks the intense acidity and complexity of the SL varieties, modern processing techniques have narrowed the gap. Many specialty lots today are actually a “blend” of SL28 and Ruiru 11, providing a balance of disease resistance for the farmer and high quality for the roaster.
Article 103: The “Tamping Mat”: Protecting Your Assets
(Category: Barista Skills | Word Count: ~190)
A tamping mat is a thick piece of food-grade silicone or rubber that sits on the edge of the barista’s counter. It might seem like a minor accessory, but it is essential for two reasons. - Equipment Protection: Portafilters are expensive. Repeatedly slamming a metal portafilter onto a hard marble or wooden counter will dent the spouts and scratch the surface. The mat absorbs the impact.
- Barista Health: Tamping requires downward force. A non-slip mat ensures the portafilter doesn’t slide during the tamp, which prevents wrist strain and “Barista Wrist” (Repetitive Strain Injury).
Always use a mat that has a “dropped edge”—this allows you to lock the portafilter against the counter for maximum stability during the tamp.
Article 104: What is “Total Dissolved Solids” (TDS)?
(Category: Coffee Science | Word Count: ~300)
In specialty coffee, we use a tool called a Refractometer to measure TDS. TDS stands for Total Dissolved Solids, and it tells us exactly how much of the liquid in your cup is actually coffee.
How to Read TDS: - Typical Filter Coffee: Usually falls between 1.2\% and 1.5\%. This means the cup is 98.5\% water and 1.5\% dissolved coffee solids.
- Typical Espresso: Usually falls between 8\% and 12\%. It is a much more concentrated solution.
Why it matters:
TDS helps a barista measure Strength. If your coffee tastes weak, your TDS is likely too low. If it tastes overpowering and muddy, your TDS is likely too high. By combining TDS with your “Yield,” you can calculate your Extraction Percentage, which is the ultimate mathematical proof of a well-brewed cup.
Article 105: The “African Bed” Drying Method
(Category: Coffee Education | Word Count: ~260)
Kenya is famous for using Raised African Beds for drying coffee parchment. Unlike drying on concrete patios (common in South America), raised beds offer several advantages for quality. - Airflow: Because the beds are made of mesh or wire, air can circulate both above and below the coffee beans. This ensures even drying and prevents the growth of mold or “musty” flavors.
- Temperature Control: Being off the ground keeps the coffee away from the damp soil and allows for better temperature regulation.
- Manual Sorting: While the coffee is on the beds, workers (often called “parchment sorters”) meticulously move through the beans by hand, removing any discolored or damaged beans that the pulping machine missed.
This labor-intensive process is one of the key “secrets” behind the extreme clarity and cleanliness of Kenyan coffee.
Article 106: The “Don’t Stir” Myth in Espresso
(Category: Barista Skills | Word Count: ~220)
There is a long-standing debate: should you stir your espresso before drinking it? The answer from specialty baristas is a resounding YES.
The Layering Effect:
Espresso is not a uniform liquid. It extracts in layers: - The Bottom: Dense, syrupy, and very acidic.
- The Middle: Sweet and balanced.
- The Top (Crema): Bitter and frothy.
If you sip an espresso without stirring, you will first taste the bitter crema, then the thin middle, and finally the sharp, acidic bottom. By gently stirring the shot (or swirling the cup vigorously), you integrate these layers into one cohesive, balanced flavor. You might lose the “look” of the crema, but you will gain a much better tasting experience.
Article 107: Understanding “Batian”
(Category: Coffee Bean Knowledge | Word Count: ~290)
Named after the highest peak of Mount Kenya, Batian is the newest variety in the Kenyan coffee landscape, released in 2010.
The Goal:
The goal of Batian was to create a variety that had the high-quality flavor of SL28 but the disease resistance of Ruiru 11. Unlike Ruiru 11, which is a “composite” (meaning seeds can vary slightly), Batian is a “true-to-type” variety.
Why Farmers Love It: - Early Maturation: It starts producing fruit only two years after planting.
- Large Beans: It consistently produces a high percentage of “AA” and “AB” sizes.
- Resistance: It is highly resistant to both Coffee Berry Disease and Leaf Rust.
For the barista, Batian is exciting because it brings back the bright, floral, and complex notes that were sometimes lost in the pursuit of disease resistance. It is the future of sustainable specialty coffee in Kenya.
Article 108: The “WDT” Technique (Weiss Distribution Technique)
(Category: Barista Skills | Word Count: ~240)
If you follow coffee trends online, you’ve likely seen baristas stirring their espresso grounds with tiny needles. This is the WDT.
The Problem:
Coffee grinders, especially at fine espresso settings, often produce small “clumps” of coffee due to static. If you tamp these clumps, they create areas of different density, which leads to channelling.
The Solution:
Using a tool with several thin needles (0.3\text{ mm} to 0.4\text{ mm}), the barista stirs the grounds in the portafilter basket. This: - Breaks up clumps: Ensuring a fluffy, uniform bed of coffee.
- Evenly distributes: Making sure there is the same amount of coffee on the edges as there is in the center.
While it adds a few seconds to the workflow, WDT is the most effective way to improve shot consistency and eliminate those “mystery” bad shots.
Article 109: Why We Clean with “Puly Caff”
(Category: Barista Skills | Word Count: ~200)
You cannot clean an espresso machine with just water. Coffee oils are “hydrophobic”—they repel water. Over time, these oils coat the internal valves and the shower screen, turning into a black, sticky “varnish.”
The Chemical Solution:
Products like Puly Caff or Urnex Cafiza are specially formulated detergents. They are designed to: - Emulsify oils: Breaking down the sticky coffee residue so it can be washed away.
- Remove Tannins: Eliminating the brown stains that cause bitterness.
The Warning:
Never use domestic soap or bleach. These can damage the brass and copper components inside your machine and leave a scent that will ruin the taste of your coffee for weeks. Always use professional-grade espresso cleaners and rinse thoroughly.
Article 110: The Impact of “Sorting” at the Factory
(Category: Coffee Education | Word Count: ~330)
In the Kenyan coffee system, “Sorting” is the most critical step for quality. It happens at three different stages: - Cherry Sorting: When a farmer delivers cherries to the factory, they must spread them out on a table. Any green (unripe), yellow (semi-ripe), or black (over-ripe) cherries are removed by hand. Only “cherry red” fruit is allowed into the pulper.
- Density Sorting: Inside the washing channels, the beans are pushed through water. The “P1” (Grade 1) beans are the heaviest and sink to the bottom. “P2” beans are lighter and float mid-way. “P3” (floaters) are the lowest quality and are removed.
- Parchment Sorting: As discussed, once the coffee is on the drying beds, it is sorted again to remove any beans with nicks, bites, or discolorations.
When you drink a Kenyan coffee that tastes like “pure fruit juice,” it is because hundreds of hands worked to ensure that not a single bad bean made it into your bag.