Here's Looking at Green Coffee

Here's Looking At Green

To an expert, green coffee is a text. It can be read bean by bean, telling the entire story of the coffee from the tree, through the processing, sorting and screening.

Click on thumbnail for larger image

One of the most complex botanical forms is a flowering tree, such as coffee. As the tree goes through its many cycles of growth and dormancy, flowering and fruiting, many critical needs must be met to ensure a plant that is happy, healthy and wants to make alot of fruit. One coffee tree produces only one pound of roasted coffee per year! The seeds are an encapsulation of all the complexities of the trees, and with over 800 organic constituents that contribute to the cup quality of the beverage, it is 2.5 times more chemically complex than wine.

I am not an expert on defects (you have to work in the industrial/commercial end of the trade to see lots of bad coffee!), but I cup and roast coffee everyday. I prepared this image (below) from coffee samples in my "green coffee files" (several sets of hardware drawers where I keep all green and roasted samples for reference) at the request of my customers. The image is not all-inclusive, and is not composed entirely of defects.

Do not misinterpret the presence of defects in a coffee as the sole indication of its quality. Dry-processed coffees will always have more defects, and an inexperienced viewer can easily interpret the presence of more silverskin (chaff) that gives the coffee a very yellow appearance as a defect.

Ultimately, the quality of a coffee is found in the cup.

Notes:

If a coffee has defective beans it doesnt necessarily mean its bad. The cup is ALWAYS the ultimate proving ground for the quality of a coffee. Some coffee by nature have a higher percentage of defects and are considered top quality.
New crop wet-processed coffees are usually a deeper shade of green, but not necessarily.
A black bean (which is also called a "stinker" in an old text I have) is a seed that fully rotted in the fruit
A "sour" bean is also called an underdeveloped bean. These are detected visually by an off color and a very wrinkled surface
Immature, underdeveloped beans are also called "floaters" because in wet-processing they float and are skimmed off the water's surface. They are also called "quakers", but i have heard of other defects also being called quakers.
Coffee is often sold at a particular screen size, such as 16 or 17/18. The presence of small and large beans compared to the norm is not a defect, but indicates some ineffectiveness in preparation.
Peaberries are not defects and are often considered higher quality, for no great intrinsic reason. They occur when one of the two ovules (or seeds/beans) aborts and the other can develop unrestricted into a round shape, filling out the space provided in the fruit.
Not pictured are beans afflicted by a boring insect (watch your Colombian closely!) and foreign matter that counts as defects such as sticks, stones, seeds in their parchment, pods, fingers ....
The Green Coffee Association has a page of defects and grading.

Three Important Questions:

What does good "new crop/ current crop" green coffee look like?
What does old green coffee look like?
Why is PAST CROP coffee getting to be a big problem in home roasting?

Firstly, good green coffee from many origins has a different look based on preparation standards, processing (wet, dry, semi, pulped, etc). The SCAA distributes a poster of the green coffee grades, but it is based upon wet-processed coffee, and is quite useless for judging other processess and odd-looking cultivars.

Furthermore, some of the worst defects are impossible to see, phenolic coffee in particular. Phenol defect is found in many origins, but is most identifiable in Colombia and Brazil (I have encountered it in Mexico, Honduras, and Nicaragua to a greater extent than in El Salvador and Guatemal ... not sure what implications can be drwan from that. No conclusive research has proven the cause of phenol in the cup, but it is one of the most obvious defects to taste. It is a dirty, sulpherous flavor, very potent both in the aromatics and cup flavors. And you cannot see it: the green and roasted seed appear as a wholesome coffee bean.

Some have posited that the cause is on the tree, in particular that it comes from trees with a consistently sunny side and a consistently shaded side. Others say it is from bad processing, that it is microbial. Others say it is the trees defence from the Broca (the coffee berry boring insect). Due to the cup experience, I side with the microbe bacteria explanation. It shares sensorial attributes with volatile sulpher compounds, such as hydrogen sulfide. Whether this occurs on the tree or in the processing is unsure. Phenol defect can be present in some of the best coffees, produced at the finest mills.

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This page is authored by Tom Owen and Sweet Maria's Coffee, Inc. and is not to be copied or reproduced without permission.

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