Freshly Roasted Coffee Beans

 

TOP 9 Green Coffee Defects That You Need To Know Now

WHAT IS A COFFEE DEFECT?

A defect is any characteristic that negatively influences the green bean’s flavour characteristics, resulting from pre-processing, processing, or even the roasting stages. On-farm, the producers can sort and remove the defective beans (coffee grading). But if a bean defect goes unnoticed, it will become evident during roasting and coffee consumption.

There are different kinds of green bean defects: some are easier to spot than others. The defects come under two categories: primary and secondary. The two defects that are difficult to spot are full defects: full black and full sour.

IMPACT OF COFFEE BEAN DEFECTS ON THE TASTE 

The taste of roasted coffee is influenced significantly by growing and processing defects in the green coffee beans. The taste varies depending on the defect, with some defects, like mouldy, sour or black beans, which make the coffee completely undrinkable. Other defects like broken beans have a minimal impact on the roasted coffee taste.

THE STANDARD COFFEE BEAN DEFECTS WITH THE MOST SIGNIFICANT IMPACT ON THE FINISHED TASTE ARE:

1. Full Black & Partial Black Beans

2. Full Sour & Partial Sour Beans

3. Broken or Chipped Beans

4. Insect damaged beans

5. Unhulled Beans

6. Quakers

7. Fungus damage

8. Shell Beans or Elephant Ear beans

9. Faded, mottled or streaked bean 

These coffee defects will ruin the taste of the coffee. 

FULL BLACK & PARTIAL BLACK BEANS

Full black is a primary defect, and partial black is a secondary defect. The beans are brown or black and shrivelled, and with the crack in the middle too wide. This coffee defect is usually the most obvious to spot and can be seen when the bean is unroasted. A few black beans can contaminate the whole batch.

Why does it happen?

Black beans occur due to a lack of full development of the bean. Fungal diseases and nutritional deficiencies can also result in this defect. 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 fertilisation

What effect does it have?

This defect can result in an off-flavour with an unpleasant aroma. The beans can taste fermented, resulting in a sour phenolic taste. The other possible flavour notes are:

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

FULL SOUR & PARTIAL SOUR BEANS

Full sour is a primary defect, and partial sour is a secondary defect. Sour beans have a light to dark brown or even yellow discolouration. These beans add a winey taste to the cup. It is possible to remove visibly sour beans due to their discolouration. Sour beans significantly affect the flavour in the cup.

Why does it happen?

The common causes include a long time lag between picking and de-pulping, over-fermentation, storing the beans with high moisture content, and dirty water. The other reasons could be:

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

What effect does it have?

These beans can create an underdeveloped, sour flavour, resulting in winey or acetic acid characteristics.

BROKEN OR CHIPPED BEANS

Chipped beans are a secondary defect, generally caused by the de-pulping machine. It is one of the most straightforward defects to spot as the beans will be either broken or have fractures. It is easy to remove Broken or chipped beans during sorting.

Why does it happen?

The pulping machinery can cause it 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

What effect does it have?

Due to the varying size of the beans, the heat transfer during the roasting stage would be uneven, resulting in the coffee beans being poorly roasted. The coffee will have an unbalanced and inconsistent flavour profile. Also, because the beans are cut open, there is a possibility of other defects developing, such as mould. The other possible taste characteristics being:

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

INSECT DAMAGE

Insect Damage is a secondary defect caused by coffee pests: the white stem borer, the coffee bean weevil, etc. Coffees damaged by the pests tend to be sour and earthy. These green beans will typically have small holes, which are also visible on the cherry during picking.

Why does it happen?

Many insects feed on the coffee while the coffee fruit is on the tree or during storage. Insects can kill the seed embryo, introducing musty and alkaline flavours in the cup. The most widespread of these pests is the white stem borer. Because of the holes, mould/fungus may start to develop.

What effect does it have?

The impact on the cup may range from a muted flavour to sour notes. The other possible flavours are: 

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

UNHULLED BEANS

Unhulled bean is a secondary defect. It leads to an earthy, bitter cup. During roasting, the hull can get burnt, damaging the other beans in the process. Many times these beans are left with pieces of husks on them.

Why does it happen?

Primarily due to poor calibration of pulping and hulling equipment. 

What effect does it have?

Large amounts of unhulled beans can lead to a range of off flavours, including earthy, fermented, mouldy or phenolic taste. There is also a risk of fire during the roasting process. The presence of unhulled beans reduces the intensity of flavour in the cup.

QUAKERS

These are unripened, small beans with a low density. They are immature and usually have silvery skin with a textured or withered surface. They are hard to spot after de-pulping but are more recognisable once roasted as they will have a lighter colour. 

Why does it happen?

Quakers occur due to poor nutrition or poor picking practices. The other possible reasons are:

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

What effect does it have?

The taste in the cup would be a dry, papery taste resulting in increased bitterness and astringency in the cup. There will also be a noticeable straw-like flavour.

FUNGUS OR MOULD

Beans infested with fungus or mould have yellow, reddish, white or grey spores on them. The most common reason for this defect is high moisture content. Hence, producers in humid environments should be cautious about using natural or honey processing methods.

Why does it happen?

Damaged beans, such as broken ones or ones with insect holes – are more susceptible to fungus infestation. Mould infects 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

What effect does it have?

You can expect earthy and over-fermented flavours in the cup with a loss of aromatic and flavour characteristics. Fungus infestation could pose a potential health risk. An obvious distinguishing factor is an antiseptic taste in the cup.

SHELL BEANS OR ELEPHANT EAR BEANS

Shells are mainly a visual defect; they occur naturally due to genetics. Shells quickly become over-roasted, which affects the taste in the cup. They render a burnt or charred flavour to the cup. For a clean cup of coffee, it is better to remove Shell beans before roasting.

 

FADED, MOTTLED OR STREAKED BEAN

The faded beans have an irregular greenish colour resulting from faulty drying or re-wetting during the drying stage. The uneven drying creates inconsistencies in the roasting stage. The flavour impact in the cup is that of reduced flavour and aroma with reduced acidity.

 

SO WHAT DOES ALL THIS MEAN TO YOU?

This list of defects gives you the ability to recognise the quality of the beans you are buying. You’ll also be able to tell if the defects are influencing the taste and by how much. 

However, no matter the processing type, post-harvest drying is the most critical stage in quality preservation and management, and errors during this hypersensitive process are evident in the cup.

If you find a few defective beans in the roast with parchment will not be doing much to your taste. A few mouldy beans, however, would affect the flavour drastically.

After assessing the coffee you’re getting for defects, you’ll start to recognise if your supplier cares what he’s selling and if that inexpensive coffee was a good deal.

Some coffees could have an excellent physical aspect, but when the beans are roasted and cupped the taste may not be appealing. Hence, green bean analysis is only one of the many quality control processes for Classic Beans.

Even if coffee makes it from picking to shipping with no problems, there are still risks for defects. Poor conditions are the other main culprit of storage-damaged coffee. It’s not rocket science—good practices and attention to detail are crucial. 

Wake up to a rich and complex cup of coffee!!

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