11 Green Coffee Defects That Affects Your Coffee Taste

As the coffee industry is doing well, you want to make sure that you are getting what you paid for when you order your daily coffee. Green coffee defects are factors that negatively affect the quality of the beans. Depending on the cause,green coffee defects can result in many problems for the coffee drinker, including poor flavor, uneven roasting, and difficulty brewing.

We want to help you save time and money by giving you the ability to evaluate your coffee. A defect in the green bean negatively affects the flavor characteristics, which can be caused by pre-processing, processing, or even roasting.

Farmers can sort and remove bad coffee beans while they are on the farm (coffee grading). But if a bean defect is not noticed, it will become evident during roasting and coffee consumption.

Different types of green bean defects exist, with some being more easily detectable than others. The defects come under two categories: primary and secondary.

Two types of defects that are difficult to spot are those that are either entirely black or entirely sour.

Impact of coffee beans defects on coffee taste

The taste of roasted coffee beans is significantly influenced by defects in the beans during the growing and processing stages.

The taste of the coffee varies depending on the defect in the bean, with some defects making the coffee completely undrinkable. Other defects that impact the roasted coffee taste include broken beans.

1. Full black and partial black beans

In theory this one is pretty straight forward. This problem is about coffee beans that come looking black. They will often impart a sour or moldy flavor.

Coffee beans are classified as “full black” when most of the bean is darker in color. If only half the bean is black, they are called “partial black”.

This fault is most often caused by over fermentation, which happens when overripe fruit is used, or the processing conditions are very imperfect.

A full black defect is the most severe, and a partial black defect is less severe. The beans are brown or black and shriveled, and the crack running down the middle is too wide.

The most obvious coffee defect to spot is when the bean is unroasted. A few black beans can contaminate the whole batch.

Black beans occur when the bean does not develop fully. Fungal diseases and deficiencies in nutrition can also lead to this problem.

The other possible reasons are listed below:

1. Over fermentation, 
2. Over-ripe cherries picked from the ground,
3. Not enough water during the growing period,
4. Under-ripe cherry with under-developed carbohydrate levels,
5. Unripe fruit dried at high temperatures
6. Poor fertilization

An unpleasant aroma can result from this defect. If the beans taste fermented, it will result in a sour phenolic taste.

The other possible flavor notes are:

1. Loss of acidity
2. Reduced flavor characteristics Weed-like or straw-like

2. Full sour and partial sour beans

The term “peaberry” is used to describe coffee beans that have a yellowish or red appearance. If you don’t like the taste of vinegar, wines with high acidity levels are probably not for you.

If more than half of the coffee bean is impacted, it is classified as “full sour.” The defect is critical because just one coffee bean can contaminate an entire pot.

Primary sour is a primary defect, and secondary sour is a secondary defect. Sour beans have a light to dark brown or even yellow discoloration. The beans may also have a powdery film on the surface.

These beans add a winey taste to the cup. You can remove beans that look sour because they are discolored. Sour beans significantly affect the flavor in the cup.

The main reasons that coffee beans can go bad are if they are not de-pulped soon after being picked, if they are fermented for too long, if they are stored with too much moisture, or if they are stored in dirty water.

The other reasons could be:

• Water contamination 
• Over recycling water 
• Dirty fermentation tanks
• Over-fermentation from slow drying

If these beans are used, the resultant flavors will be sour and undeveloped. This gives the wine a ‘winey’ or ‘acetic acid’ taste.

3. Broken or chipped beans

Secondary bean defects are usually caused by the de-pulping machine. The most obvious sign of this defect is either broken or fractured beans.

Sorting beans is easy because you can simply remove the broken or chipped ones. The machinery used to turn the coffee beans into pulp can cause defects during the de-pulping, drying, and other processes. Low moisture content could be a contributing factor.

The other possible reasons being:

1. Harvesting under-ripe, undersized beans
2. Processing under-ripe coffee through pulping machines
3. Poor machinery calibration in the dry mill

If the coffee beans are different sizes, the heat won’t be distributed evenly during roasting, resulting in poorly roasted beans.

The coffee will not have a uniform flavor. There is also a possibility that other defects, such as mold, will develop because the beans are cut open.

The other possible taste characteristics being:

1. Reduced aromatics
2. Reduced acidity
3. Scorching during roasting 

4. Insect damage

Coffee beans sometimes show signs of insects that have drilled into them.

This is considered a defect because it could mean that insects have laid eggs or developed larvae in the bean or fruit, which would give it a sour and unpleasant flavor.

coffee bean damage caused by pests like the white stem borer and coffee bean weevil results in coffees that taste sour and earthy.

The holes on these green beans are typically small, as are the holes on the cherries picked during harvest.

There are many insects that feed on coffee while it is still on the tree or during storage. Insects can introduce Off flavors to the coffee by killing the seed embryo.

The most common of these pests is the white stem borer. Because of the holes, mold/fungus may start to develop. The taste of the cup may be affected by the impact, ranging from a muted flavor to sour notes. The other possible flavors are:

1. Fermented taste
2. Dirty Moldy taste
3. Phenolic taste

5. Unhulled beans

The Cherry defect is when the coffee beans still have a layer of parchment or hull attached to them. This happens because of machinery problems.

Unhulled bean is a secondary defect. It leads to an earthy, bitter cup. If the hull of the bean gets burnt during roasting, it can damage the other beans in the process. Oftentimes, these beans are left with fragments of husks still attached to them.

This is primarily caused by poor calibration of the pulping and hulling equipment. Too many unhulled beans can give your coffee an earthy, fermented, or mouldy taste.

The roasting process also poses a fire hazard. The less intense flavor in the cup is due to the presence of unhulled beans.

6. Quakers

These are unripened, small beans with a low density. They are not fully developed and usually have pale skin that is rough or wrinkled. The coffee beans that have been de-pulped are harder to spot, but they are more recognizable once roasted. This is because they will have a lighter color.

Quakers occur when birds are not given proper nutrition or when they are not picked properly. The other possible reasons are:

1. Cultivation in unsuitable coffee production regions
2. Lack of sufficient fertilizer application
3. Coffee trees that are affected by drought and rust disease
4. Failure to remove unripe berries during sorting

The cup would have a dry, papery taste that would make the coffee more bitter and astringent. There will also be a noticeable straw-like flavor.

7. Fungus or mold

If there are yellow, reddish, white, or grey spores on the beans, they are infested with fungus or mold. The most common reason for this defect is that the moisture content is too high. Therefore, those who produce in humid environments should be careful about using natural or honey processing methods.

Beans that are damaged are more likely to be infested with fungus. Mold affects an entire batch of coffee as the spores spread from one bean to another.

The reasons behind this occurrence are:

1. Overly long fermentation periods, 
2. Interruptions during drying, 
3. Storing beans with high moisture content,
4. Harvesting and processing of fallen coffee berries that have been in contact with the ground
5. Leftover beans in harvest sacks contamination newly picked berries

If you drink this coffee, you will likely taste strong, natural flavors and weak or no aromatic scents. Fungus infestation could pose a potential health risk. The taste of the coffee is noticeably different when an antiseptic is used.