wunder beta☕ Coffee: extraction, roasting and the perfect cup
Why the same beans make brilliant and bitter coffee: grind, temperature, time and the chemistry of extraction.
What you’ll learn
- What is actually in the cupDistinguish brew strength from extraction yield and explain why coffee's flavours dissolve in a fixed order.A cup is about 98.7% water; strength is how much coffee dissolved into the liquid and extraction yield is what fraction of the grounds you dissolved, and the two move independently.
- From cherry to green beanDescribe how coffee grows, how the fruit is removed, and why species and altitude appear on the bag.Coffee is a seed from a fruit; washed, natural and honey processing set the base flavour, and arabica grown high and slow carries the acids and sugars speciality roasters want.
- Roasting builds the flavourExplain how roasting creates coffee aroma, what first crack marks, and why freshness fades so fast.Maillard reactions, caramelisation and chlorogenic acid breakdown build hundreds of compounds in minutes; the roast level trades origin character for roast flavour, and staling starts immediately.
- Grind, water and timeUse grind size, ratio, time, temperature and water quality to move a brew toward the sweet spot.Grind sets surface area and must match contact time; sour means under-extracted and bitter means over-extracted, and even the water's mineral content changes what dissolves.
- Espresso, caffeine and what nobody has settledExplain espresso as a pressurised extraction, describe how caffeine acts on adenosine receptors, and identify coffee's biggest open risk.Espresso uses about nine bars through a fine puck for around thirty seconds; caffeine blocks adenosine receptors and clears slowly, and coffee's narrow genetics leave it exposed to rust and warming.
Questions this course answers
Your filter coffee tastes sour and thin. Which change is most likely to fix it?
Sourness is the signature of under-extraction: only the fast-dissolving acids made it into the cup. A finer grind exposes more surface area, so more of the sugars and browning compounds follow the acids out.
Put these in the order water pulls them out of the grounds
Because dissolution is ordered, the taste of a cup tells you where you stopped. Sour means you caught only the start; bitter and drying means you ran into the tail.
Roughly what percentage of a cup of filter coffee, by mass, is dissolved coffee rather than water?
A well-made filter coffee is around 1.3% dissolved solids - so about 98.7% of what you drink is water. Espresso is far more concentrated, at roughly 8 to 12%.
Match each brewing choice to what it mainly changes
Strength and extraction are separate dials. Ratio moves intensity; grind, time and temperature move how much of each dose you dissolved.
Why does a dark roast taste stronger but not deliver much more caffeine?
Caffeine survives roasting almost unchanged. What deepens with a dark roast is the roast flavour and bitterness, which most people interpret as strength.
Complete the sentence about freshness
The same surface area that speeds up extraction also speeds up oxidation. It is why grinding immediately before brewing outperforms almost any other equipment upgrade.
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