Optical Sorting Q&A

optical sorting

What is the color sorter?
A color sorting machine is used to remove inconsistencies in products through exactly what it sounds like: sorting by color. They are used in almost every agricultural grain product out there. Ever wonder how every single rice grain in a bag of rice is consistent in color? Or peanuts? Beans? Corn? That’s right! They are sorted by color. For the coffee industry in particular, a large percentage of the green unroasted coffee we buy goes through a color sorter before export. This is why it comes in so darn beautiful and consistent.

Is the color sorter for green coffee or roasted coffee?
Theoretically, we could run green coffee through our machine, but that is not the intention. The high standard of green quality remains unchanged for Counter Culture. The sorter is for roasted coffee, which is unique in the coffee industry. We’re using a Bühler Sortex in our East Coast roastery and a Satake Sorter in our West Coast facility.

Why does the roasted coffee need sorting?
In countries that export green coffee, exporters use density tables, hand-sorting, and color-sorting machines for preparing our coffees to the highest standards for export. But even with the best coffees in the world, the absolute best milling possible cannot make them perfect. Especially when it comes to roast consistency and quakers. Quakers are the primary focus of what we are sorting out.

What is a quaker, and why sort it?
Quakers are beans that develop much slower in the roaster and come out bright yellow or tan while the rest of the coffee becomes brown. This happens because a quaker contains less of the organic materials that cause browning reactions—particularly carbohydrates and sugars. Many times this is because the coffee was picked underripe, but it is also possible to pick a coffee perfectly ripe and still get quakers. Diseases like leaf rust affect plant health, and we have seen a significantly higher number of quakers in coffees whose trees suffered from disease. Even coffees we know are 100 percent picked ripe.

Will it remove all quakers?
While the color sorter is really good, it is never going to be perfect. Our goal is to have a 97 percent reduction in quakers. That doesn’t mean we get every single quaker, nor does it mean that all of the removed coffee is imperfect.

Does it sort out potato defect?
This type of optical sorting technology does not have the capacity to sort out potato defect. We’ve been collecting and analyzing data to determine how to objectively test for the defect and are now working on sharing the results industry-wide through conferences and research papers. We’ve also been collaborating with scientists to figure out a way to detect the defect in coffee before it’s roasted so that it can be sorted out.

How much will it take out of your coffees?
We have been testing this technology for about two years now, and, for the most part, we sort out from 0.5–5 percent. With more than 90 percent of our coffees, the amount removed will be 2 percent or less. A few coffees will have higher percentage removed. Natural sundried coffees, in particular, have a higher rate of quakers that will be taken out.

How calibratable is the machine?
Infinitely. That is why Counter Culture has staff members specifically dedicated to running our optical sorters. Someone has to program the sorting profile into the machine. This involves doing lots of hand sorting and adjustments to the optical “eye” used to identify bad beans. The better the calibration and the creation of the profiles used to sort, the better and more efficient it runs.

What about rocks, nails, and other material sometimes found in coffee?
An additional benefit to sorting is that it adds another step of filtering foreign material. The model Counter Culture’s Durham facility is using sorts by color and shape. We have seen it take out rocks and other things that can be bad for grinders. However, once again, it will not be 100 percent perfect, but it will improve day by day.

What do you do with the sorted out coffee?
Counter Culture re-roasts and donates the coffee that is sorted out to local organizations.

This machine sounds awesome, but was the coffee not good before?
Yes! And coffees will be even better after going through the sorter. We are pushing ourselves to be better, and taking some risk with this technology. The color sorter is not a cure-all, and coffees from Counter Culture that are not going through the machine are still awesome. We are proud of this step forward, but there will still be a few quakers here or there—even when the machine is running perfectly. Nobody is perfect, not even the color sorter.

Have you been able to calculate how much it has improved your coffee?
It’s hard to quantify exact gains related to quality scores, but we know that the coffee we’re removing is below both our quality standards and specialty coffee standards. We know that removing these inconsistencies is making our coffee more-consistently delicious.