A quaker is an underdeveloped coffee bean that stays pale when you roast it. A coffee color sorter removes quakers by sight: cameras look at every roasted bean, compare its color to the standard you set, and a short puff of air blows the pale ones out of the stream. It matters because a single quaker can flatten the sweetness of a cup, and because no person can check every bean in a batch by hand. With a color sorter, roasted coffee defect removal covers every bean, on every batch.
Every roaster knows the moment. The batch drops into the cooling tray, and among all the brown beans sits one that is pale and tan, as if it had skipped the roast. You pick it out. Then you spot a second one, and a third, a fourth, and it never stops until it's time to discharge the batch.
That pale bean is a quaker. It is one of the most common defects in roasted coffee and one of the hardest to keep out of the bag. This article explains where quakers come from, what they do to the cup, and how color sorting removes them.
A quaker is a bean that never finished developing. It did not build up the sugars that a healthy, ripe bean has. In the roaster, those sugars are what turn a bean brown, so a bean without them stays pale while everything around it darkens.
Most quakers start with a coffee cherry that was picked before it was ripe. But ripe picking alone doesn't rule them out. A cherry can look perfectly ripe on the outside and still hold an underdeveloped bean, for example after a drought or when the plant was short of nutrients. That is why quakers turn up even in carefully hand-picked lots that score very high.
The hard part is that you can't see this coming. In green coffee, a quaker looks almost like any other bean, which is why even careful sorting at origin lets some through. The defect only shows itself after the roast. We go deeper on the causes in our guide to quakers in coffee.
A quaker tastes the way it looks: flat, dry, and papery; many of our customers describe it as a note of peanut. It brings no sweetness to the cup and takes some away from the beans around it.
What makes this serious is how few beans end up in a cup. A 15g filter brew is made from roughly 100 beans, and already one or two quakers in the dose are enough to dull it. Your customer will never see a pale bean. They will just taste a coffee that is a little less sweet than the last bag, and wonder what changed. That is why we say one bad bean is one too many.
Coffee defect identification by machine rests on one simple fact: a quaker is lighter in color than the beans around it. A color sorter is built to see that difference on every single bean.
The roasted coffee flows through the machine in a thin stream, so that each bean passes the cameras on its own. The cameras capture every bean, and the software compares its color to the standard you have set for that coffee. A bean that is lighter than your standard is marked as a reject. So is a bean that is too dark, such as a burnt one.
The SOVDA Pearl Mini uses two cameras to check every single coffee bean, so a Quaker that looks fine from one side is still seen from the other.
Once a bean is marked, a short puff of air pushes it out of the falling stream. The good coffee carries on, the rejects land in a separate bin, and nobody has to touch a bean.
You stay in charge of the standard the whole time. You might set it strict for a competition lot and a little more relaxed for a blend. With Pearl Mini, you decide what gets rejected, and most roasters, like Onyx, Coffee Collective or Black & White, reject 1–2% of a batch.
It is worth keeping an eye on that reject bin, because it tells you a lot about a lot. If a coffee suddenly throws more rejects than it used to, you have a good question for your green supplier, and you can use it to renegotiate pricing or build more trust with the farmers you work with directly.
Because checking every bean by hand is simply not possible. A 15 kg (33 lb) batch holds roughly 100,000 beans. Even the most careful person at the cooling tray only sees the beans that happen to lie on top, for the few minutes before the next batch needs them.
So hand sorting is always a sample. You pick out the quakers you notice and hope the rest of the batch looks the same. How many you catch depends on the light, the hour, and who is standing at the tray that day. None of that is a question of care. Your team can hold your standard perfectly in their heads and still have no way to hold every bean against it.
A coffee color sorter closes that gap. It looks at every bean in the batch and holds each one to the same standard, from the first batch of the day to the last. This is what roasted coffee quality control comes down to: knowing that everything in the bag was actually checked. And your roaster's eyes can go back to the roast.
Quakers are the main target, but they are not the only ones. A color sorter also removes burnt beans and light stones.
The light stones surprise many roasters, because that sounds like a job for the destoner. A destoner separates stones from coffee by weight, and that works well for a dense stone. But some stones are light and full of air, like a crumb of concrete or a chip of patio stone. A stone like that weighs about the same as a coffee bean, so the destoner carries it along with the coffee. A color sorter doesn't weigh anything. It sees that the stone is the wrong color and blows it out.
The two machines do different jobs, which we explain in Color Sorter vs Destoner: Do You Need Both?
A color sorter sees color. It doesn't taste. It can't rescue a roast that went wrong, and it can't find a defect that looks just like a good bean. A few good beans will also end up in the reject bin alongside the bad ones, which is normal for any sorter. Our Coffee Color Sorter Buying Guide explains why that happens and how to compare machines.
If you own the roastery, sorting makes you less dependent on perfect green. You can buy an excellent lot that others pass on because of a few quakers, and you can stay with your producers through a hard harvest. Whatever you buy, only what passes your standard goes out with your name on the bag.
If you run production, coffee bean sorting stops depending on who is on shift. Every bean of every batch gets checked, and your team spends less of the day picking through cooling trays and more of it on work that needs them.
Tim Wendelboe, Black & White, Coffee Collective and SEY sort with Pearl Mini.
What is a quaker in coffee? A quaker is an underdeveloped coffee bean that stays pale after roasting. It lacks the sugars that turn a healthy bean brown, and it tastes flat, dry and papery.
What causes quakers in coffee? Most quakers come from cherries that were picked before they were ripe. Some come from cherries that looked ripe but held an underdeveloped bean, for example after a drought or when the plant was short of nutrients.
How do you remove quakers from roasted coffee? You can pick them out by hand or run the coffee through a color sorter. A color sorter checks every bean with cameras and blows the pale ones out with air.
Can you remove quakers before roasting? Mostly not. In green coffee, a quaker looks almost like a healthy bean. It only shows its pale color after roasting, so quakers are sorted after the roast.
Can a destoner remove quakers? No. A destoner is built to catch stones, and a quaker is coffee. It passes through with the good beans. Removing quakers takes a color sorter.
Does a destoner remove all stones? No. A destoner separates stones by weight, so it catches dense stones. Light, airy stones, like a crumb of concrete or a chip of patio stone, weigh about the same as a coffee bean and pass through. A color sorter catches them by color.
How much coffee does a color sorter reject? That is your decision, because you set how strict the standard is. With Pearl Mini, most roasters reject 1–2% of a batch.
Is color sorting better than hand sorting? It is more consistent, because it checks every bean. A person at the cooling tray can only check the beans they see, so hand sorting is always a sample of the batch. A color sorter holds every bean to the same standard.
Do the world's best roasters use color sorters? Yes. Tim Wendelboe, Black & White, Coffee Collective and SEY sort with Pearl Mini.
Want to know what sorting would take out of your coffee? Talk to Sales and we'll look at it together.