Pod or capsule machine

What was in 43 capsules

Sourced

A Swiss group bought 43 different capsules of one shape, all for the same machine, opened some and brewed the rest to a fixed 40 gram drink. These are the lowest and highest values in their table.

One capsule format on one machine at one drink size, from capsules on sale when the study was done. The ranges describe that sample. Other systems use different doses, pressures and drink sizes, and nothing here transfers to them.

What decided how strong the drink was

Sourced

The authors conclude that the most efficient ways to raise the dissolved solids in the drink are to put more coffee in the capsule or to grind it finer, with the limit that too fine a grind restricts flow excessively. Neither is in the buyer's hands.

Their new finding was about fines. For capsules of similar median particle size, those with a larger share of very small particles took longer to extract, and they propose that share as a second number that has to be known to understand how a capsule will behave. Longer extraction went with stronger drinks; the weight of coffee in the capsule showed no relation to the percentage extracted.

Three certified tasters agreed a score for each coffee for flavour, acidity, body and balance, on a scale from 5 to 10 on which 6 stood for average. Most scores sat close to 6 and did not follow the technical measurements. The authors read this as showing that most of the capsules were made to a similar standard, and they note two capsules with more oxygen inside that scored lower, and two single-origin coffees that scored higher.

The path of the water

Widely documented

How a pressure-capsule system works in outline. Systems differ in detail and makers describe their own.

Sealed, but not all sealed alike

Sourced

A capsule holds ground coffee, which loses its gas and aroma far faster than whole beans once exposed. The seal is the whole point. In the 43-capsule study nearly all had 1 per cent oxygen or less inside. One had about as much as ordinary air, which means that capsule's coffee was effectively unprotected.

A separate study from the same institute followed chemical markers of freshness in four commercial capsule systems during storage. Those made with a layer of aluminium preserved the markers better than those without. That was a chemical measurement, and the authors said research was continuing into whether it shows in the cup.

Recyclable, compostable: what one assessment modelled

Sourced

Claims about capsule packaging are claims, and they depend on what happens after the capsule leaves the kitchen. One life cycle assessment, of pods used on a university campus in the United States, shows how much turns on that. It compared the packaging of a plastic pod with that of a compostable one, each counted as the packaging for one 8-ounce serving, and nothing else: the coffee inside, the machine and its electricity were outside what it modelled.

On energy used to make and dispose of the packaging, the plastic pod sent to landfill came out lowest. Across ten other environmental measures the picture changed, and the worst case in eight of the ten was a compostable pod that ended up in landfill instead of a composting facility. In a trial at the campus's industrial composting site the compostable pods broke down completely within 46 days.

These are modelled results for one place. The same paper reports an earlier assessment of drip, French press and pod coffee, which CoffeeHQ has not opened, as finding single-serve pods to have a lower impact than drip filter coffee, and as warning that the different amounts of coffee each method uses can shift the burden from one stage to another. The authors themselves note that studies of pods differ so much in boundaries, methods and scale that their results cannot be laid side by side. So the studies do not agree on a verdict, and this page gives none. The certification the authors describe as relevant in the United States is to standards for industrial composting, which is not the same thing as breaking down in a garden heap.

The few things you can change

CoffeeHQ explanation

Thin and bitter when run into a large mug

Usually because: A capsule holds five or six grams of coffee. Running a long drink through it passes a lot of water through very little coffee.

Change first: Run the short programme and top up with hot water afterwards.

Americano

Weak, whatever the setting

Usually because: The dose is fixed, so strength can only come from using less water.

Change first: Shorten the drink, or use two capsules for one cup.

Coffee too weak

Tastes flat or stale from a new box

Usually because: It may be the capsule. The study above found one capsule on sale with as much oxygen inside as ordinary air, and two with more oxygen that scored lower when tasted.

Change first: Try a different brand before blaming the machine.

Looking after one

Widely documented

There is little to do: empty the used-capsule drawer, rinse the drip tray, and run water through the brewing head now and then. Scale builds up in any machine that heats water. How often to descale, with what, and whether the machine tells you, are the maker's instructions for that model; follow those and not a general rule.

Where the evidence on capsules stops

CoffeeHQ explanation

It names no brand and recommends none. It does not say capsule coffee is better or worse than other coffee: the one tasting read found the scores bunched together and unrelated to what was measured. It gives no pressure for capsule machines, since none was read from a measurement. It does not say whether capsules are greener or less green than other ways of making coffee; the assessment described covers packaging alone. It says nothing about aluminium or plastic and health. And every figure in the first table belongs to one capsule format.

What to do next

• Pod machine or bean-to-cup? — The other one-button way to make espresso-style coffee, and what each fixes for you.
• Pressure and flow in espresso — What resistance and flow do in an espresso bed, which is what a capsule is in miniature.
• Grind size — Why a grind is a spread of sizes, and why the share of fines matters.
• Why coffee goes stale — The packaging study in full, including what the aluminium layer did.
• Sustainability claims — How to tell a measured result from a modelled one and from a seller's statement.
• Become a barista — A structured programme from dose and grind through milk, drinks and maintenance.