Espresso grinders

What Is a Single-Dose Espresso Grinder, and What Does Zero Retention Mean?

Published · By the Espresso Shortlist editors · Prices and specs as of that date, from the pages under Sources

Summary

A single-dose grinder is built to be loaded with the beans for one drink at a time and ground empty, instead of holding a stock of beans in a hopper. For that to work, little coffee can stay inside after grinding, which is why makers advertise "zero" or "low" retention. Those words are claims. Eureka, which sells its single-dose grinders under the Zero name, lists retention of about 0.55 g.

The single-dose routine

You weigh the beans for one shot, pour them in, and grind until nothing is left. The loading space is small on purpose. Eureka's single-dose Mignon models take 45 g of beans, compared with 300 g in the hopper of the Mignon Specialità. Niche describes the Zero as a single-dose grinder into which you "pour your beans into the funnel," with 63 mm conical burrs and a stepless dial.

Zero retention, in numbers

Retention is the coffee left in the grinder after a dose. If you switch from one bag to another, whatever was left behind ends up in your next shot.

Niche lists "Zero retention" for the Zero and describes a straight-through design that "leaves no grind behind," without giving a figure. Eureka publishes one. Its Mignon Single Dose Pro, which it markets with "Brand new ZERO-retention grind chamber," lists a maximum retention of 0.55 for espresso and 0.05 for brew, with no unit printed. The Mignon Zero 65 All Purpose gives "approximately 0.55 g" in total. Against an 18 g dose, 0.55 g is about 3 percent.

How the grinders get it that low

Eureka credits a tilted body, 15° on the Single Dose Pro and 5° on the Zero 65, combined with an improved grinding chamber, and on the Zero 65 a top burr without holes. Its single-dose models also have the Blow Up system, which Eureka describes as "eliminating the retention with a blow." Niche credits its straight-through design.

The payoff Eureka states is dose consistency, ±0.15 g for espresso on the Single Dose Pro. Niche gives less than ±0.2 g for the Zero, based on independent test data.

When a hopper is the easier routine

A hopper grinder keeps beans loaded, so the next dose is a button press, with no weighing or pouring. If the whole household drinks the same espresso blend all week, that saves a step every morning, and retention matters less because the coffee left inside is the same coffee.

Shopping for one? Shop espresso grinders →

Sources

  1. Niche Coffee — Niche Zero
  2. Eureka — Mignon Single Dose Pro
  3. Eureka — Mignon Zero 65 All Purpose
  4. Eureka — Mignon Zero
  5. Eureka — Mignon Specialità

We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.

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