How Cold Press Juicers Work

A cold press juicer is a screw turning slowly inside a perforated tube. Produce goes in the top, the screw drags it along and crushes it against the holes, juice goes through and fiber comes out the end. That is the entire mechanism, and understanding it explains every strength and every annoyance the category has.

The three names mean one machine

• Masticating is the mechanical description. The auger chews produce rather than cutting it.
• Slow juicer is the honest plain-English version. Our registry runs 43 to 110 RPM against 6,500 to 18,000 for centrifugal machines.
• Cold press is the marketing term. Nothing in a home juicer is pressed cold in the industrial sense -- the phrase stuck because slow crushing generates less heat and less aeration than a fast basket.

A listing using all three is describing one machine three times. It is not a feature list.

The four parts that matter

The auger

A tapered screw, usually a hard plastic or a composite. It does two jobs at once: it pulls produce in, and because it tapers, it progressively reduces the space available, which is what applies the crushing pressure. Omega states a triple-stage auger on the J8006HDS and a dual-edge auger on the VSJ843 -- those describe different approaches to the same job.

The screen

A perforated tube or basket, usually fine mesh. Juice passes through; fiber does not. This part determines how much fine pulp ends up in the glass, and it is also the slowest thing to wash, which is why the premium end of the category has started removing it. Hurom's Easy Clean design has no mesh strainer; Cuisinart's CSJ-300 uses a mesh-free filter.

The back-pressure

At the far end there is a restriction that stops fiber falling straight out, so the auger has something to squeeze against. On most machines this is fixed. On Omega's NC900HDC it is adjustable -- Omega states five end-cap pressure settings -- which is the only documented extraction control anybody publishes.

The chute

The least glamorous part and the one that most affects your daily life. A 45 mm chute, as Hurom states for the H400, means chopping. Kuvings states 3.5 in on the REVO830 plus a 1.75 in auto-cut chute specifically for celery and carrots. Chute width is the spec to read.

Why this mechanism suits fiber

A celery stalk is long structural strands with liquid held between them. An auger grips a strand and crushes along its length, releasing that liquid. A spinning basket cuts across the strand at high speed, which mostly just relocates it -- so the strand arrives in the pulp bin largely intact and still wet.

On a hard apple the difference narrows considerably, because an apple is dense cell water rather than structural fiber and both mechanisms get at it. That is why we keep saying the mechanism question is really a produce question. Masticating vs centrifugal is the full comparison.

Why it jams, and what reverse does

The auger pulls fiber in faster than it can crush it, the space ahead fills up, and the motor stalls. Celery is the usual culprit because the strands are long enough to wrap the auger rather than being carried along it.

A reverse function turns the auger backwards, which unwinds the wrap and lets the blockage fall back out of the chute. Nutribullet and AMZCHEF both state one. Without it you are taking the drum apart. Juicer clogging fixes covers the technique that prevents it in the first place.

What the mechanism does not explain