Continuing our Green Bean Series, this month we’ll address defects in wet-processed Arabica coffee beans; their cause, how to identify them and the effect they have on the roast.
Our “Tools for Roasters – Green Bean Series” is a five-part evaluation of how the characteristics of green coffee beans affect the roast outcome.
Roasters who consistently buy premium coffees of strictly the best quality may have rarely faced defects, while most roasters find them far too often, even when presented with what are sold as “specialty” coffees. “.
The fact is that any one of these dozens of defects will negatively affect the quality and alter the taste of the coffee you are producing. These defects are both identifiable and preventable.
The defects in this article are different than the “forming” defects we talked about in a previous article.
With that in mind, our goal is to give you a very direct and accurate identification of what these defects look like, their causes, and how they can affect your roast profile.
The twelve key flaws to watch out for:
- Discolored Beans
- amber beans
- Battered Beans
- damaged green water
- damaged pulper
- damaged insect
- Immature Beans
- crafty beans
- triple center cuts
- stinky
- over-fermented
- sick
PAST BEANS
Wilted beans can be the result of over-drying or excessive moisture absorption, depending on the environment. Either way, wilted beans have little resistance to environmental factors.
The effect on the roast is that they give a dull roast regardless of the roast profile. The result is a smooth bean with flavors of moisture and wood in the cup. And, the percentage of moisture loss will be very high. The color of these beans is pale brown, whitish.
They are normally the result of beans that have a high moisture content (11% – 13%) and when stored in a warehouse they will tend to dry out. In the drying process, and since they are not in contact with direct sunlight, these grains tend to wither.
Instead of drying out, these beans are actually rotting and growing mold inside. It is these molds that cause the beans to over-dry, producing their pale brown to off-white color.
Additionally, during the drying of wet or dry processed beans, the coffee can be adversely affected if it is not adequately exposed to sunlight at the proper stage of the drying process.
Another cause is when the coffee has been dehulled with a hammer mill. In this case, the kernels will come out dull in color as a result of the outer cells being bruised and microscopic dust penetrating the outer layer of the kernels.
A final factor that can contribute to coffee discoloration is old coffee that has been sitting in a warehouse for two to three years or more, causing the beans to dry out, develop mold, and other negative consequences.
AMBER BEANS
These beans have a brilliant bright golden color. The cause is due to mineral deficiencies in the soil (including iron).
When you roast these beans, the cup will lack acidity, with a rough, flat body and a bitter taste. Also, the roast produced by these beans will have a very dull color.
COATED BEANS
These beans have a sticky, silvery skin caused by domination or being affected by drought. The features of these beans look whitish, rough, and show microscopic lines of silvery skin.
In the roasting process, you will experience soft beans with excess chaff. Roasting can result in negative effects in the cup, including excessively high grass, hay, earth, wood, greenish, and potato flavors.
DAMAGED GREEN WATER
These are fully processed beans that, when hulled, come into contact with water where a chemical reaction occurs, turning them a greenish color. This situation causes the beans to become moldy and toxic.
DAMAGED PULPER
In the process of going through the pulping machine, the coffee beans can get stuck, creating excessive pressure that causes the beans to be damaged.
These injured beans will burst and then begin to oxidize slightly, become contaminated with water, and over-ferment, causing mold that results in earthy, leathery, and musty flavors.
Also, roasted beans will be uneven; some will split, while others will appear round and mixed in with the solid kernels.
DAMAGED INSECT
Berry moths inject the coffee cherry in the egg-laying process, creating a needle-shaped black hole.
Anthestia insects damage beans and bruise them, producing rough black to yellow spots.
Beans with this type of insect damage will roast lightly and tend to shrink, creating overbearing musty, alkaline, and salty flavors.
IMMATURE BEANS
Picked immature, often as a result of prevailing and drought-affected conditions, immature bean characteristics include a rough surface and greenish color with a sticky silvery skin and will usually have thin edges.
Roast will be very dull, with open center cuts, soft beans, and subsequently no acidity, heavy body, with greenish and herbaceous flavors.
These beans can also give rise to Quakers in the roast; visible only after roasting by their pale appearance and peanut butter flavor. Avoiding the purchase of immature beans is the best way to avoid contamination by these defective beans.
FOX BEANS
As you can imagine, the name comes from the color of a red fox.
This rusty red color is usually caused by the beans being overripe. These beans tend to have a dead embryo and will give you fruity, fermented, and nutty flavors.
TRIPLE CENTER CUTS
These are misshapen beans caused by malnutrition due to drought-affected conditions or lack of minerals, creating irregular beans with multiple cuts down the center.
During roasting, these beans can split open into their double or triple center cuts. They are brittle, soft and highly permeable; that will over-roast, creating a heavy body, flat cup, and smoky, burnt flavor.
STINKS
Stinker beans may have normal formation, but have a dead embryo and are yellow in color due to over-fermentation and/or over-ripeness. If they are crushed, broken or cut when raw, they put off an order which is very unpleasant.
Even one or two stinkers in your roast can ruin the whole batch and give you a gross cuppa.
OVER-FERMENTED
These beans look dirty and have a tobacco color.
When roasted you will get a sour, pulpy taste and a dirty, filthy cup; with the smell of rotten meat or stable. If only slightly over-fermented, your roast can impart sour and oniony flavors.
SICK
These defects are due to coffee being affected by various diseases such as CBD (coffee berry disease) and leaf rust.
When the disease attacks a coffee farm, the mother plant will produce premature beans. This will affect the berry before it is ripe, usually at the milk stage, and the kernels will not develop at all or only partially develop, with a very small berry or no berry within the parchment within the cherry.
The deformed part of these beans looks brown to very dark brown in color, often with deformities resembling a splintered piece where the bean is left with dark brown markings that go deep into the bean. The deformed part of these beans is generally scaly and irregularly shaped.
These diseased little beans will only partially develop, but can still be harvested and ended up mixed with other beans of normal quality and then sold on the market.
THEN WHAT DO YOU DO?
- First, avoid these nasty flaws when buying green coffee whenever possible.
- Second, educate your customers on the tastes inherent in a quality cup. An uneducated palette can even get used to overly fermented, moldy, rancid, peanut butter and other flavor defects that are actually toxic when ingested into the human body!
- And continue your quest to create the perfect roast!