Kenya Coffee School
Foundation Diploma
Barista Skills & Specialty Coffee
Coffee Origins & History
From the highlands of Ethiopia to the cup — the story of coffee’s journey around the world.
The Legend of Discovery
The most widely accepted origin story places coffee’s discovery in Kaffa, Ethiopia around 850 CE. The legend of the goat herder Kaldi describes goats becoming unusually energetic after eating berries from a particular shrub. Monks at a nearby monastery brewed a drink from the berries and found they could remain alert through long evening prayers.
The word “coffee” is derived from the Arabic qahwa, which in turn may derive from “Kaffa” — the Ethiopian kingdom where coffee was first discovered. The Oromo people of Ethiopia were the first to recognize coffee’s stimulant properties.
The Spread of Coffee
Sufi monks in Yemen were among the first to cultivate coffee systematically. Port of Mocha became the world’s first major coffee trading hub. The word “mocha” still refers both to Yemen’s port city and to chocolate-flavoured coffee drinks today.
Qahveh Khaneh (coffeehouses) emerged throughout the Arab world as centres of intellectual exchange, debate, music and chess. They were sometimes called “Schools of the Wise.”
Coffee reached Constantinople (Istanbul) around 1555. By 1650, coffeehouses spread across Europe. London’s first coffeehouse opened in 1652. Lloyd’s of London insurance market and the London Stock Exchange both grew from coffeehouses.
The Dutch broke the Arab monopoly by smuggling live plants to Java (Indonesia) in 1616. The French brought coffee to Martinique (1720), from which Brazil’s enormous industry grew. Coffee became a colonial commodity — often produced through enslaved labour.
Erna Knutsen first used the term “specialty coffee” in 1974. The Specialty Coffee Association of America (SCAA, now SCA) was founded in 1982. The “Third Wave” movement, emerging in the 2000s, treats coffee as an artisanal product with traceable origin, terroir, and craft preparation.
Coffee Growing Regions — The Bean Belt
Coffee grows within the Bean Belt (or Coffee Belt), a band roughly between the Tropics of Cancer and Capricorn (approximately 25°N–25°S latitude). Ideal conditions include:
Arabica prefers cooler 15–24°C; Robusta tolerates 24–30°C.
Higher altitude = slower cherry maturation = greater complexity of flavour.
Well-distributed throughout the year, with a dry season for harvesting.
Volcanic, well-drained soils rich in organic matter. Kenya’s red volcanic soils are prized.
Major Producing Countries
| Region | Key Countries | Typical Flavour Profile |
|---|---|---|
| East Africa | Kenya, Ethiopia, Tanzania, Rwanda, Burundi | Bright acidity, berry, citrus, floral, wine-like complexity |
| Central America | Guatemala, Costa Rica, Honduras, Panama, El Salvador | Balanced, chocolate, nuts, mild fruit, caramel |
| South America | Brazil, Colombia, Peru, Bolivia | Low acidity, nuts, chocolate, heavy body (Brazil); bright citrus (Colombia) |
| Southeast Asia | Indonesia, Vietnam, Myanmar, Philippines | Earthy, spice, dark chocolate, full body, low acidity |
| Arabia | Yemen | Wine, dried fruit, complex spice, wild fermented notes |
The Coffee Plant & Processing
From seed to cherry to green bean — understanding the agriculture behind the cup.
Species & Varieties Exam Key
| Species | Caffeine | Altitude | Flavour | % World Production |
|---|---|---|---|---|
| Arabica (C. arabica) | 1.0–1.5% | 600–2,500m | Complex, aromatic, sweet, acidic | ~60% |
| Robusta (C. canephora) | 2.0–2.7% | 0–800m | Strong, earthy, harsh, rubbery, bitter | ~40% |
| Liberica (C. liberica) | Variable | Low altitude | Woody, smoky, floral — very unusual | <1% |
Key Arabica Varieties in Kenya
- SL28 — Developed by Scott Laboratories; drought-resistant; renowned for blackcurrant, wine-like acidity and high cup quality
- SL34 — Also from Scott Labs; larger bean; performs well at high altitude; complex fruit and heavy body
- Ruiru 11 — Developed by Kenya’s Coffee Research Station; disease resistant (CBD, leaf rust); compact plant; lower cup quality than SL varieties
- Batian — Newer release from Coffee Research Institute of Kenya (CRK); CBD and leaf rust resistant; good cup quality; rapidly maturing
- K7 — Older variety; resistant to leaf rust; grown at lower altitudes
Anatomy of the Coffee Cherry
Working from the outside in, a coffee cherry consists of the following layers:
The red (or yellow/orange in some varieties) outer skin of the cherry that ripens over 6–12 months.
A sweet, sticky fruit flesh — the mucilage. This is where sugars ferment during processing, influencing final cup flavour significantly.
A thin protective layer encasing the seed. Remains on the bean during “honey” and “natural” processes until milling.
A very thin membrane clinging to the bean. Most burns off as “chaff” during roasting.
The actual coffee seed — what is roasted, ground and brewed. Usually two beans per cherry (flat side facing each other). A “peaberry” is a single rounded bean, occurring in ~5–10% of cherries.
Processing Methods Exam Key
Washed (Wet Process)
Cherry skin and pulp are removed mechanically (pulping), then the bean is fermented in water tanks for 12–72 hours to break down remaining mucilage, then washed thoroughly and dried on raised beds. Result: Clean, bright, high acidity, terroir-expressive cups. Kenya predominantly uses the washed process.
Natural (Dry Process)
Whole cherries are dried in the sun on raised beds or patios for 2–6 weeks, with regular turning. Fermentation occurs inside the fruit. Result: Heavy body, low acidity, intense fruity/winey/berry flavours. Common in Ethiopia and Brazil. Risk of defects if drying is uneven.
Honey Process
Skin removed but varying amounts of mucilage left on the bean before drying. Classified by mucilage level retained: Yellow Honey (least), Red Honey, Black Honey (most). Result: Middle ground — more body and sweetness than washed, more clarity than natural. Popular in Costa Rica, El Salvador.
Wet-Hulled (Giling Basah)
Indonesian method. Parchment is removed while the bean still has high moisture content (30–50%), then dried. Result: Very low acidity, heavy body, earthy/spicy flavour. Characteristic of Sumatra and Sulawesi coffees.
Kenya’s double-fermentation washed process is unique. After initial pulping, beans are fermented for 12–36 hours, then soaked in clean water for a further 12–24 hours (the “soaking” stage). This extended contact is thought to contribute to Kenya’s characteristically complex, wine-like acidity and clean cup.
Roasting & Grading
Transforming raw green beans into the aromatic, soluble coffee we brew.
The Roasting Process
Roasting is a complex series of chemical reactions driven by heat. During a typical roast (12–15 minutes for drum roasters), green beans lose 15–20% of their weight (moisture, CO₂) and increase in volume by up to 60%.
Key Roasting Stages
| Stage | Bean Temp | What Happens |
|---|---|---|
| Drying Phase | ~20–160°C | Moisture evaporates; beans turn yellow then tan; grassy, hay-like aromas |
| Maillard Reaction | ~150–175°C | Amino acids + sugars react; browning begins; bread/toast aromas develop; most flavour complexity built here |
| First Crack | ~196–205°C | Steam/CO₂ pressure causes audible cracking (like popcorn). Light roast begins here. |
| Development | Post-crack | Time between first crack and desired end point — critical for flavour balance. DTR (Development Time Ratio) = development time ÷ total roast time |
| Second Crack | ~224–230°C | Cellular structure fractures again; oils migrate to surface; darker, oilier; roast character dominates over origin character |
Roast Levels
Bright acidity, origin flavours dominant, no oil on surface, higher caffeine (less mass lost), best for filter.
Balanced acidity and body, caramel sweetness, some origin character. Versatile — works for espresso and filter.
Oily surface, low acidity, bitter, roast flavours dominate, smoky/dark chocolate. Origin character largely lost.
Caramelisation (sugar breakdown, ~170°C+) and the Maillard reaction (amino acid + sugar, ~150°C) are both responsible for browning and flavour development. Roasting also creates over 800 volatile aroma compounds from approximately 250 present in green coffee.
Kenya Coffee Grading System Kenya
Kenya grades coffee primarily by bean size (screen size) and cup quality, with the auction system rewarding superior grades with higher prices.
| Grade | Screen Size | Description |
|---|---|---|
| AA | 18 (7.22mm) | Largest bean; considered premium; commands highest prices at auction; what Kenya is famous for globally |
| AB | 15–16 (6.0–6.40mm) | A + B combined; still high quality; approximately 30% of Kenya’s crop |
| PB (Peaberry) | Round | Single seed per cherry; often sweeter and more concentrated than flat beans; premium specialty grade |
| C | Below 15 | Smaller beans; lower quality; domestic market |
| E (Elephant) | >20 | Very large; rare; two beans fused together |
| TT | 14–15 | Light beans separated by density; lower quality |
| T | Varies | Small broken beans; lowest export grade |
| MH/ML | Varies | Mbuni (natural/dry process) coffees; Heavy/Light; distinct flavour profile |
Espresso Science
The physics, chemistry, and craft behind the perfect shot.
What is Espresso?
Espresso is a concentrated coffee beverage brewed by forcing hot water (88–96°C) through finely ground, compacted coffee at 8–10 bars of pressure, typically producing 25–35ml of liquid in 25–35 seconds.
Industry standard; some modern machines use pressure profiling (varying 1–15 bar during extraction).
Lighter roasts often benefit from higher temp (94–96°C); darker roasts, lower temp (88–92°C).
Total time from start of pump to end of shot. Adjust by changing grind size.
Grounds (dose) to yield (liquid out). 1:2 is classic. Ristretto ~1:1.5; Lungo ~1:3+.
The Golden Triangle of Variables Practical
Three variables are most directly within the barista’s control and must be balanced:
Dose — Mass of ground coffee in the portafilter basket (typically 7–25g depending on basket size). ↑ Dose = more resistance, slower extraction, more body.
Grind Size — Finer grind = more surface area = faster extraction, more flavour compounds extracted. Coarser = faster flow, under-extraction risk.
Yield / Output — Mass of liquid espresso produced. Combined with dose, defines brew ratio.
Additional variables: Water temperature, pressure profile, tamping pressure (typically ~15–20kg, but consistency matters more than specific weight), pre-infusion, coffee freshness, humidity.
Extraction Theory
During espresso extraction, compounds dissolve in a specific order: acids → sugars → bitter compounds. This is why over- and under-extraction produce distinctly different fault profiles.
| Condition | Extraction % | Taste | Fixes |
|---|---|---|---|
| Under-Extracted | <18% | Sour, sharp, thin, salty, lacking sweetness | Grind finer, increase dose, increase temp, slow the shot |
| Ideal | 18–22% | Balanced: sweet, bright, complex, full body | — |
| Over-Extracted | >22% | Bitter, hollow, astringent, dry, harsh | Grind coarser, reduce dose, lower temp, speed the shot |
Total Dissolved Solids (TDS) measures the concentration of a brewed coffee. Extraction Yield (EY) measures what percentage of the ground coffee’s mass ended up dissolved in the cup. Specialty coffee targets EY of 18–22% and TDS of 8–12% for espresso. Tools like a refractometer can measure TDS.
The Espresso Machine Practical
Key Components
- Boiler / Heat Exchanger / Dual Boiler — Heats water for brewing and steam. Dual boilers allow independent temperature control for each.
- Pump — Vibration pumps (common in home machines) or rotary pumps (commercial, quieter, consistent) generate 9 bar pressure.
- Group Head — Where portafilter locks in; delivers water to the puck. E61 group heads are self-thermosyphon, providing temperature stability.
- Portafilter — The handle-and-basket assembly. Single (7–10g), double (14–22g), naked/bottomless (no spouts — allows observation of extraction).
- Steam Wand — Creates pressurised steam for texturing milk.
- PID Controller — Electronic temperature controller maintaining consistent brew temperature.
“Espresso is not a roast, not a blend, not a bean — it is a method.”SCA Brewing Standards
Milk Technique & Espresso Drinks
The art of steam — texturing milk and building the espresso menu.
Milk Steaming Science Practical
Steaming milk transforms its structure by denaturing proteins and incorporating air, creating the silky “microfoam” essential to lattes, cappuccinos and latte art.
Milk Composition
Fat molecules coat air bubbles, stabilising foam and adding creaminess and sweetness.
Whey proteins (especially β-lactoglobulin) denature at ~70°C and form a stable foam network.
Lactose sweetness is enhanced by heat — this is why steamed milk tastes sweeter than cold milk.
Steaming Technique Steps
Release a quick burst of steam to expel condensation from the wand tip before inserting into milk.
Tip just below surface, slightly off-centre. Tilt jug ~30° to encourage a whirlpool motion.
Lower the jug so the tip is just at or breaking the surface — introduces air. Do this quickly (first few seconds). Listen for a paper-tearing hissing sound. This is where you add volume.
Submerge tip slightly deeper to stop aeration and create a rolling whirlpool that integrates the foam. This breaks down large bubbles into microfoam.
Target 60–65°C. Milk proteins begin to break down above 70°C, creating a scalded, bitter taste. Use thermometer or palm-check (uncomfortably hot to hold = ~60–65°C).
Purge wand again after use, then immediately wipe with a dedicated damp cloth. Milk proteins bake onto the wand quickly and harbour bacteria.
Espresso Drink Guide
| Drink | Espresso | Milk / Other | Notes |
|---|---|---|---|
| Ristretto | 15–20ml | None | Short, concentrated; 1:1 to 1:1.5 ratio; sweeter, less bitter |
| Espresso | 25–35ml | None | Standard single shot; classic 1:2 ratio |
| Lungo | 50–60ml | None | Long shot; 1:3+ ratio; more bitter, extracted longer |
| Americano | 25–35ml | Hot water (100–150ml) | Espresso + hot water; espresso added to water (not reverse) preserves crema |
| Macchiato | 25–35ml | ~15–20ml microfoam | Espresso “stained” with a dollop of foam. Can be latte macchiato (milk stained with espresso) |
| Cortado | 25–35ml | 25–35ml steamed milk | 1:1 ratio; reduces acidity without diluting significantly |
| Flat White | Double (50–60ml) | 100–130ml microfoam | Stronger espresso ratio than latte; silky thin microfoam; originated in Australia/NZ |
| Cappuccino | 25–35ml | Equal parts steamed milk + dry foam | Traditional: 1/3 espresso : 1/3 steamed milk : 1/3 foam (120–150ml total) |
| Latte | 25–35ml | 150–200ml steamed milk | Most milk-forward; canvas for latte art; thin layer of microfoam on top |
| Mocha | 25–35ml | Chocolate sauce + 150ml milk | Add chocolate to espresso before milk; can top with whipped cream |
Latte Art Fundamentals Practical
Latte art requires well-textured microfoam (glossy, no visible bubbles, paint-like consistency), a properly prepared espresso with intact crema, and controlled pouring technique.
- Heart — Foundation pattern; pour into centre, then cut through with a quick through-pour
- Rosette — Wiggle the jug while pouring, moving forward; cut through at the end
- Tulip — Pour several “blobs” in sequence, each pushing the previous; cut through
- Milk must be between 60–65°C — overheated milk loses the protein structure needed for art
- Start the pour from a height (~10cm) to sink espresso, then lower the jug close to surface (<2cm) to float the foam
Filter & Manual Brewing
Exploring the diverse world of pour-over, immersion, and other brewing methods.
Brew Variables — Universal
Filter coffee. 1:15 = stronger; 1:17 = lighter. Starting point: 1:16 (60g coffee per litre of water).
Just off boil. Lighter roasts: 94–96°C; Darker: 90–92°C. Never boiling (100°C).
Same as espresso; measured via TDS refractometer. Dial in using ratio, grind, and temp.
Mineral content matters. Distilled water = flat taste. Too many minerals = chalky. Avoid chlorinated tap water.
Manual Brewing Methods
Pour-Over / V60 (Hario)
A conical dripper with a large single hole and spiral ridges. Paper or metal filter. The classic pour-over method for specialty coffee.
- Grind: Medium-fine
- Ratio: 1:15 to 1:17
- Bloom: Saturate grounds with ~2× coffee weight water; wait 30–45s (allows CO₂ to degas, improving extraction)
- Pours: Slow, controlled circular pours maintaining a consistent water level
- Total time: 2:30–3:30 minutes
- Result: Clean, bright, high clarity, terroir-expressive
Chemex
Hourglass-shaped glass vessel with thick proprietary paper filters that remove oils and fine particles entirely.
- Grind: Medium-coarse (thicker filters require coarser grind for flow)
- Result: Very clean, clarity-forward, delicate, paper-filtered body — excellent for light roasts and bright African coffees
- Total time: 4–5 minutes
AeroPress
Plastic immersion + pressure brewer. Versatile, durable, travel-friendly. Invented by Alan Adler (2005).
- Grind: Medium-fine (or vary widely by recipe)
- Can be used with standard or inverted method
- Steep time: 1–2 minutes; then press over ~30s
- Result: Clean but richer body than pour-over; lower acidity; very forgiving
- Annual AeroPress World Championship held globally
French Press (Cafetière)
Full immersion; metal mesh filter; retains all coffee oils; produces a heavy, full-bodied cup.
- Grind: Coarse (to prevent silt passing through mesh)
- Steep: 4 minutes; plunge slowly; serve immediately (coffee over-extracts if left on grounds)
- Result: Heavy body, oily mouthfeel, rich, low clarity; can be muddy at the bottom
Moka Pot (Stovetop)
Three-chamber stove-top brewer using steam pressure (~1–2 bar) — not a true espresso but produces a very concentrated, strong brew.
- Grind: Medium-fine (not as fine as espresso)
- Fill lower chamber with hot (pre-boiled) water to just below valve
- Do not tamp the coffee; fill the basket loosely and level
- Remove from heat as soon as coffee starts flowing to prevent burning
Cold Brew
Coarse ground coffee steeped in cold or room-temperature water for 12–24 hours. No heat involved.
- Grind: Extra coarse
- Ratio: 1:8 (concentrate) to 1:15 (ready-to-drink)
- Result: Very low acidity, smooth, sweet, heavy body; shelf stable 7–14 days refrigerated
- Different flavour compounds extracted (heat is a solvent — cold extraction favours different molecules)
Cupping & Sensory Evaluation
The standardised language and practice of tasting coffee professionally.
SCA Cupping Protocol Exam Key
Cupping is the standardised method of evaluating coffee quality developed by the SCA (Specialty Coffee Association). It allows fair comparison of multiple coffees on a level playing field.
Cupping Setup
8.25g ± 0.25g coffee per 150ml water; grind coarser than filter (to avoid over-extraction during long steeping); grind fresh immediately before cupping.
Assess the ground coffee’s aroma before adding water. Note at 0–4 minutes after grinding (aromatics dissipate quickly).
Pour water at 93°C ± 3°C directly onto grounds, filling to the top. Start timer. Do not stir.
At 3–5 minutes, assess the wet crust’s aroma. Then break the crust by pushing through it with a spoon 3 times, smelling as you do.
Remove foam and floating grounds from the surface using two spoons.
When cups have cooled to ~70°C, aspirate (slurp) coffee loudly from a spoon. Slurping aerosolises the liquid, coating all taste receptors.
Continue evaluating as temperature drops. Many flavours, defects, and characteristics reveal themselves differently at different temperatures. Final scores taken when cups reach room temp.
SCA Cupping Score Sheet Attributes
The SCA 100-point score sheet evaluates 10 attributes, each scored 6–10 (with 6 = good, 7 = very good, 8 = excellent, 9 = outstanding, 10 = extraordinary). Coffees scoring 80+ are classified as Specialty Coffee.
| Attribute | What It Measures |
|---|---|
| Fragrance / Aroma | Dry grounds (fragrance) and wet brew (aroma); intensity and quality of scent |
| Flavour | Overall impression of all taste and aroma sensations experienced mid-palate |
| Aftertaste | Length and quality of positive flavour sensations remaining after swallowing |
| Acidity | Brightness or liveliness; quality (pleasant vs harsh/sour) not just intensity |
| Body | Weight and texture of the liquid in the mouth (thin → syrupy → heavy) |
| Balance | How well flavour, aftertaste, acidity, and body complement each other |
| Uniformity | Consistency across 5 cups of the same coffee (2 points deducted per inconsistent cup) |
| Clean Cup | Absence of negative impressions from first taste through aftertaste (2pts deducted per cup) |
| Sweetness | Full-bodied, pleasant sweetness; not just sugary (2pts deducted per cup) |
| Overall | Holistic assessment; personal impression beyond the above attributes |
Flavour Wheel & Tasting Vocabulary
The SCA Coffee Taster’s Flavour Wheel (updated 2016 with World Coffee Research) provides a common tasting vocabulary. Categories from the centre out move from general to specific.
Primary Flavour Families
Kenyan AA and AB coffees are renowned for their distinct blackcurrant, cassis, and dark berry notes, intense wine-like or tomato-juice acidity, full body, and clean finish. SL28 especially produces signature blackcurrant notes from the compound methyl salicylate and organic acids including citric, malic, and tartaric acids.
Primary Taste Receptors
The human tongue perceives five basic tastes. Coffee activates all of them:
| Taste | Receptor Trigger | In Coffee |
|---|---|---|
| Sweet | Sugars, glycerol | Caramelised sugars from roasting; fruity natural coffees |
| Sour / Acid | H⁺ ions (pH) | Organic acids: citric, malic, acetic, tartaric, phosphoric, chlorogenic |
| Bitter | Alkaloids, phenols | Caffeine, trigonelline, chlorogenic acid lactones; intensified by over-extraction/dark roast |
| Salty | Na⁺, K⁺ ions | Mineral salts from water; small amounts naturally in coffee |
| Umami | Glutamate | Some aged / fermented coffees; contributes to body and savouriness |
Kenya Coffee Excellence
The auction system, growing regions, and what makes Kenya one of the world’s great origins.
Kenya’s Coffee Industry Structure Kenya
Kenya produces predominantly Arabica coffee, accounting for roughly 0.5–1% of global production but consistently commanding among the highest prices at auction for its cup quality.
High altitudes with volcanic soils produce Kenya’s signature acidity and complexity.
Majority of Kenya’s coffee is produced by smallholder farmers organised into cooperatives (FCS societies).
Nairobi Coffee Exchange (NCE) holds weekly auctions. The auction system is a key quality driver — farmers are rewarded for better grades.
Main crop (Oct–Dec) and fly crop (June–August) allow two harvesting periods annually.
Key Growing Regions
| Region | Notes | Flavour Characteristics |
|---|---|---|
| Nyeri | Aberdare Range foothills; considered Kenya’s finest region; home to Tetu, Othaya, Mathira cooperatives | Blackcurrant, full body, bright acidity, complex, wine-like |
| Kirinyaga | Slopes of Mt. Kenya; rich volcanic soil; Ngariama, Kabare cooperatives | Berry, citrus, tomato, clean and bright |
| Murang’a (Muranga) | Former Fort Hall; south of Mt. Kenya; Kambu, Gatanga | Floral, light citrus, delicate sweetness |
| Embu | Eastern Mt. Kenya slopes; Runyenjes, Kavutiri cooperatives | Fruity, winey, complex |
| Kiambu | Closest to Nairobi; Thika, Ruiru; early centre of Kenya’s colonial coffee industry | Balanced, chocolate, mild fruit |
| Meru | North of Mt. Kenya; higher altitude; Mieru, Karama | Stone fruit, floral, light body |
| Bungoma / Trans-Nzoia | Western Kenya; Mt. Elgon slopes | Fuller body, earthy, fruit |
| Machakos / Makueni | Eastern Kenya; lower altitude; drier climate; natural/dry processed coffees more common | Earthy, bold, full body |
The Nairobi Coffee Exchange (NCE)
Kenya operates a unique auction system through the Nairobi Coffee Exchange. Coffee is sold through licensed marketing agents to licensed traders and exporters at weekly Tuesday auctions. The system is designed to:
- Ensure transparency and competitive pricing for farmers
- Enable buyers (local and international) to cup samples before bidding
- Reward quality — better-graded, better-cupping coffees command premium prices
- Maintain traceability (lot numbers can be traced back to specific cooperatives / factories)
Kenya’s coffee sector has undergone reforms to allow Direct Trade and private sales alongside the auction, giving progressive cooperatives and estates more flexibility to sell directly to international specialty buyers.
Cooperative System & Wet Mills
Most smallholder coffee in Kenya is processed at cooperative-owned wet mills (called “factories”). Farmers deliver ripe cherries to the wet mill, which pulps, ferments, washes, and dries the coffee. The cooperative then prepares it for auction.
- Farmers are shareholders in their cooperative societies (FCS — Farmer Cooperative Societies)
- Payment is made to farmers after auction proceeds are received, minus cooperative deductions
- Some estates operate their own private wet mills for full control of processing
- Kenya’s double-fermentation wet process is managed at this level
Café Operations & Barista Skills
Running a professional coffee bar — equipment, workflow, service, and hygiene.
Grinder Fundamentals Practical
The grinder is arguably more important than the espresso machine. Inconsistent or poor grind = inconsistent extraction, regardless of machine quality.
Grinder Types
| Type | Burrs | Use | Quality |
|---|---|---|---|
| Blade Grinder | Spinning blade (not true burrs) | Home (budget) | Poor — inconsistent particle size, heat damage |
| Flat Burr | Two parallel discs | Commercial espresso | Excellent uniformity; can retain heat (important in high-volume settings) |
| Conical Burr | Cone inside a ring | Filter & espresso | Excellent; runs cooler; less retention; preferred for specialty |
Always dial in the grinder when changing to a new coffee, after significant changes in temperature or humidity, after cleaning the grinder, and whenever extraction time drifts from target. Ground coffee exposed to air goes stale in minutes; whole beans last days to weeks sealed.
Coffee Freshness & Storage
- Roast date matters — peak flavour for espresso: 5–21 days post-roast (CO₂ needs to off-gas). Filter: 7–30 days. After 4–6 weeks, flavours significantly diminish.
- Degassing — Freshly roasted beans release CO₂ (stale gas) for days. This is why espresso shots from very fresh beans may be irregular — CO₂ disrupts extraction. One-way valve bags allow CO₂ out without letting O₂ in.
- Enemies of freshness — Oxygen, moisture, heat, and light all degrade coffee. Store in airtight opaque containers at room temperature.
- Freezing — Acceptable for long-term storage only if coffee is vacuum-sealed and frozen in single-use portions. Never refreeze.
Water Quality for Coffee
Water makes up ~98–99% of a brewed coffee. Its mineral content profoundly affects extraction.
| Parameter | SCA Target | Effect if Off |
|---|---|---|
| Total Hardness (CaCO₃) | 50–175 mg/L (ppm) | Too soft = flat, sour; Too hard = dull, chalky, scale builds up |
| Total Dissolved Solids | 75–250 mg/L | Too low = under-extracted; Too high = over-extraction or off flavours |
| pH | 6.5–7.5 (neutral) | Acidic water = sour notes; Alkaline = flat, muted acidity |
| Chlorine | None (0 mg/L) | Chlorine suppresses aroma; tastes medicinal; damages equipment |
| Magnesium | ~10 mg/L ideal | Magnesium ions are excellent flavour carriers in coffee extraction |
Café Hygiene & Food Safety
- Backflush espresso machine daily with clean water and weekly with cleaning detergent (e.g., Cafiza/Puly Caff)
- Clean group heads, baskets, and portafilters — coffee oils oxidise and turn rancid, adding bitter off-flavours
- Steam wand — purge before and after each use; wipe immediately with dedicated damp cloth; soak tip periodically to dissolve milk protein deposits
- Milk handling — fresh cold milk only; never reheat milk twice (protein structure breaks down, creating off-flavours and bacterial risk); discard unused steamed milk
- Grinder cleaning — brush regularly; deep clean with grinder-specific tablets (e.g., Grindz) or disassemble and wash monthly
- Drip trays — empty and clean daily to prevent bacterial growth and drain blockages
- Temperature logs — maintain records for food safety compliance
- Cross-contamination — use colour-coded cloths; never use milk cloths on machine bodies; separate tools for food handling
Sustainability & Ethics in Coffee
Understanding certifications, value chain, climate challenges, and responsible sourcing.
The Coffee Value Chain
Coffee passes through many hands between the farmer and the cup. Understanding this chain is essential for responsible sourcing.
Grows, harvests, and often processes coffee. Receives the smallest share of the final retail price — typically 5–10% in conventional trade.
Processes cherries (in Kenya’s case); organises farmers; prepares coffee for market.
Prepares coffee for export; handles logistics, documentation; may or may not add value.
Purchases and imports green coffee; specialty importers often build direct relationships with producers.
Purchases green coffee; roasts to spec; sells to cafés or directly to consumers.
Final preparation and service. The barista is the last person to affect quality before the consumer.
Certifications & Trade Models
| Certification | Focus | Notes |
|---|---|---|
| Fair Trade | Economic equity | Guarantees minimum price floor ($1.40/lb conventional); premiums for social projects; farmers organised in democratic cooperatives |
| Organic | Environmental / health | No synthetic pesticides or fertilisers; lengthy certification process; not always accessible to smallholders |
| Rainforest Alliance | Environmental & social | Merged with UTZ (2018); covers biodiversity, farmer livelihoods, climate resilience |
| Bird Friendly (Smithsonian) | Biodiversity | Shade-grown requirement; highest environmental standard; protects bird habitat and biodiversity |
| Direct Trade | Relationship-based | No third-party certification; roaster buys directly from farm; ideally higher prices + greater transparency; quality-focused |
Climate Change & Coffee
Climate change is the most significant long-term threat to coffee production. Rising temperatures are pushing the viable growing altitude for Arabica higher, reducing available land. Erratic rainfall, prolonged droughts, and increased prevalence of pests and diseases (coffee leaf rust — Hemileia vastatrix; coffee berry disease — Colletotrichum kahawae) are already affecting yields. Studies suggest up to 50% of current coffee-growing land may become unsuitable by 2050 under high-emissions scenarios.
- Shade-grown coffee — Tree cover reduces soil temperature, retains moisture, supports biodiversity, and reduces need for chemical inputs
- Drought-resistant varieties — Breeding programmes (e.g., Kenya’s Batian, Ruiru 11) developing resistant cultivars
- Agroforestry — Intercropping coffee with food crops and trees for resilience and income diversification
- Water conservation — Eco-pulpers reduce water use in wet processing by 80–90% vs traditional methods
- Carbon sequestration — Coffee farms as carbon sinks when properly managed with tree cover
The Barista’s Role in Sustainability
- Know your coffee’s origin — ask suppliers for traceability information
- Minimise waste — dial in carefully to avoid discarding shots unnecessarily; properly portion milk
- Energy efficiency — turn machines on before service, off after; use eco-modes where available
- Compost coffee grounds — nitrogen-rich; excellent for soil amendment and local gardens
- Choose certified or direct-trade coffees where possible — vote with purchasing power
- Educate customers — a knowledgeable customer values and pays for quality, benefiting farmers up the chain
“The best cup of coffee is one that is good for everyone in its journey — from the soil to the cup.”Kenya Coffee School — Foundation Diploma Ethos
Quick Reference — Key Numbers to Know
Essential figures for the Foundation Diploma exam and practical assessments.
Minimum score on the 100-point cupping sheet to qualify as specialty coffee.
For both espresso and filter. Below = under-extracted; above = over-extracted.
Industry standard pump pressure. Some machines use 7–12 bar with pressure profiling.
Above 70°C = scalded proteins; below 55°C = under-textured, weak flavour.
Standard water temperature for the SCA cupping protocol.
The standardised dose-to-water ratio for professional cupping evaluation.
60g coffee per litre of water (1:16) as SCA Golden Cup standard for filter brewing.
Typical target shot time. Adjust grind to hit this with your target yield.
Optimal window to use coffee after roasting for espresso. 7–30 days for filter.
Created during roasting from ~250 precursor compounds in green coffee.