Buying and Troubleshooting

Coffee Fundamentals

Course 1 · Chapter 10 · Buying, Storing and Troubleshooting

Storing Coffee

Storage advice in the sources is thin. Wikipedia's Coffee roasting article, covered in Coffee Fundamentals 4, gives an optimal shelf life of about two weeks for roasted coffee and about 15 minutes for ground coffee. It also says green coffee can be stored about 12 to 18 months in a climate-controlled setting before quality loss is noticeable, and that whole roasted beans can stay fresh up to a month if kept cool (marked "citation needed" on the page). Roasted coffee gives off carbon dioxide, so bags with a one-way valve let gas out. The Coffee article has a photo caption for a bag with a ziplock and one-way valve "to prevent mold". Coffee Fundamentals 5 explained why ground coffee goes stale faster: more surface is exposed.

What I could not verify

The pages I read do not say whether to keep coffee in a fridge or freezer, which container is best, or how light affects it. Many guides give firm advice on these; I have not checked any of it, so I give none here (check).

Buying

What the course has already shown gives a short buying checklist. Each point links to a chapter, and the numbers are from that chapter's sources.

Look for	Why (chapter)
Species	Arabica is sweeter, robusta more bitter with 40 to 50 percent more caffeine (Coffee Fundamentals 1)
Origin and harvest	Where and when it grew shapes the cup; specialty coffee varies from harvest to harvest (Coffee Fundamentals 2 and 9)
Processing method	Dry, washed, honey or wet-hulled change the cup (Coffee Fundamentals 3)
Roast level	Lighter keeps more acidity; darker is less dense (Coffee Fundamentals 4)
Whole beans	Ground coffee loses freshness fast, so grind at home (Coffee Fundamentals 5)
Roast date, not just best-before	Optimal shelf life is about two weeks after roasting (Coffee Fundamentals 4; check whether the bag prints one)

The Coffee article says specialty coffee has driven demand for traceable coffee, such as single-origin or single-farm lots. Some roasters trade directly with producers, or "fairly trade" without certification, usually only for high-quality coffee, and some coffee is sold through competitions and online auctions, which can make final prices more transparent.

Ethical Labels

Wikipedia's Fair trade coffee article defines the coffee as certified to fair-trade standards, aiming for greater equity in international trade and prohibiting child or forced labour. The Coffee article says fair trade labelling, which guarantees growers a negotiated price before harvest, began in the late 1980s with the Max Havelaar Foundation in the Netherlands. Fairtrade International sets standards and its subsidiary FLO-CERT certifies; the article names competing labels as Bird-Friendly Coffee, Rainforest Alliance and UTZ Certified.

Out-of-date prices, mixed evidence

The minimum prices on the page (for example 1.40 per pound for arabica) come from 2011 to 2013 sources and are likely outdated, so I do not quote them as current. The evidence on impact is mixed: one study found certification has generally had little effect on wages, farmers often cannot sell all their output as fair trade, and critics call it ethical consumerism. A 2005 Belgian study cited in the Coffee article found most respondents unwilling to pay the 27 percent premium. The labels are a starting point, not a verdict (check).

Decaf

Wikipedia's Decaffeination article says caffeine is removed from the green beans, before roasting. The legal standard varies:

Place	Standard
United States (FDA)	At least 97 percent of the caffeine removed
European Union	Green beans 99.9 percent caffeine-free by mass
Canada	Less than 0.1 percent caffeine (decaf instant coffee less than 0.3 percent)

A 2006 study found decaf drinks typically retain 1 to 2 percent of the original caffeine, sometimes as much as 20 percent. The main methods are an organic solvent (direct or indirect), water (the Swiss Water method, 8 to 10 hours, using green coffee extract and activated carbon), triglyceride soaking in coffee oils, and supercritical carbon dioxide (about 300 atmospheres and 65 °C). The methods aim to leave flavour precursors as close to their original state as possible. So decaf is not caffeine-free, though much lower.

How Much Caffeine?

The Coffee article gives 40 mg per 100 ml for typical brewed coffee and 212 mg per 100 ml for restaurant espresso, notes that 3 to 4 cups a day (300 to 400 mg of caffeine) do not pose health risks for adults, and mentions possible risks including increased bone fracture risk in women and risk to pregnancy. It also quotes the American Heart Association (2026) saying up to five cups a day, about 400 mg, may benefit cardiovascular health in some people. This is general information, not medical advice; ask a doctor about your own situation.

Code: Caffeine and Decaf Arithmetic

The script turns those figures into amounts. I ran it to get the output shown.

def caffeine_mg(volume_ml, mg_per_100ml):
    return volume_ml / 100 * mg_per_100ml

print(f"240 ml brewed at 40 mg/100 ml: {caffeine_mg(240, 40):.0f} mg")
print(f"30 ml espresso at 212 mg/100 ml: {caffeine_mg(30, 212):.0f} mg")
print(f"Brewed volume holding 400 mg: {400 / 40 * 100:.0f} ml")
print(f"3-4 cups of 240 ml brewed: {3 * caffeine_mg(240, 40):.0f}-{4 * caffeine_mg(240, 40):.0f} mg")

for removed in (0.97, 0.999):
    print(f"{removed:.1%} removed from 100 mg leaves {100 * (1 - removed):.1f} mg")

print(f"Fair trade share 2004: {24222 / 7050000:.2%}, 2005: {33991 / 6685000:.2%}")

# Output
240 ml brewed at 40 mg/100 ml: 96 mg
30 ml espresso at 212 mg/100 ml: 64 mg
Brewed volume holding 400 mg: 1000 ml
3-4 cups of 240 ml brewed: 288-384 mg
97.0% removed from 100 mg leaves 3.0 mg
99.9% removed from 100 mg leaves 0.1 mg
Fair trade share 2004: 0.34%, 2005: 0.51%

What the output shows

Per drink, a 30 ml espresso (64 mg) holds less caffeine than a 240 ml cup of filter coffee (96 mg), even though espresso is much stronger per millilitre. The 3 to 4 cups give 288 to 384 mg, consistent with the article's 300 to 400 mg. The fair trade shares match the 0.34 and 0.51 percent the article gives. The article also gives a 1979 espresso figure of 100 mg per 45 to 60 ml, which is a different measurement from 212 mg per 100 ml (about 64 mg for 30 ml versus about 100 mg per 45 to 60 ml); these are not reconciled (check).

Troubleshooting the Whole Course

Symptom	Likely cause (from the course)	Where to look
Bitter, harsh	Grind too fine, water too hot, or left on grounds	Coffee Fundamentals 5, 6 and 7
Weak, thin	Grind too coarse or too little coffee	Coffee Fundamentals 5 and 6
Gritty cup from a press	Grounds too fine for the filter	Coffee Fundamentals 7
Flat, stale	Ground long ago or roasted weeks ago	Coffee Fundamentals 4 and 5
Different every day	Measuring by scoop, not weight; uneven grind	Coffee Fundamentals 1 and 5
Slow-draining filter	Grind too fine	Coffee Fundamentals 5
Espresso too fast or too slow	Dose, grind, or pressure off the reference shot (the sources give targets, not fixes)	Coffee Fundamentals 8 (check)

What You Can Do Now

You can say where coffee comes from and why, how processing and roasting change the seed, why grind size and ratio matter, and how the main brewing families differ. You know the language professionals use to taste it and some of the questions to ask when buying. The course relied on a handful of reference pages, so treat the figures as a starting point and trust your own tasting.

Not Yet Verified, and Sources

Sources. Wikipedia articles Coffee (second part, characters 100,000 to 200,000 of about 251,000), Decaffeination and Fair trade coffee, plus earlier chapters' articles. The last quarter of the Coffee article was still not read. Sources were seen through a summarising tool.
Not in the pages read. Storage advice for fridge, freezer, containers and light, and how to read bag labels such as roast dates (all marked check).
Out of date. The fair trade minimum prices are from 2011 to 2013 and are not quoted as current.
Not reconciled. The espresso caffeine figures in the Coffee article (212 mg per 100 ml versus 100 mg per 45 to 60 ml).
Health. The caffeine and health statements are the article's summary, not medical advice.

Exercises

Exercise 1

Write a five-point plan for buying and keeping coffee, using only the chapter's sources. Mark any point that goes beyond them with "(check)".

→ Solution

Exercise 2

Use the script to find the caffeine in a 350 ml brewed coffee and in two 30 ml espressos, and the caffeine left in 250 mg of beans' worth at the FDA 97 percent and EU 99.9 percent standards. Run it and compare.

→ Solution

Exercise 3

A cup tastes bitter, thin and stale all at once. Using the troubleshooting table, list the three most likely causes, one change for each, and the order in which you would try them. Explain your order.

→ Solution

Quick Reference

Freshness: roasted about two weeks, ground about 15 minutes, green 12 to 18 months
Decaf: US 97 percent removed; EU 99.9 percent; made on green beans
Caffeine: brewed about 40 mg per 100 ml; 3 to 4 cups a day reported as no risk for adults
Labels: Fairtrade, Bird-Friendly, Rainforest Alliance, UTZ; mixed evidence
Troubleshooting: weigh, grind fresh, adjust one thing at a time

Course complete

This is the last chapter of Coffee Fundamentals. Revisit chapters 5 to 7 whenever a brew goes wrong.