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7 common defects of green coffee and how manufacturers prevent them


Defects of green coffee beans can negatively impact the manufacturer’s business. If serious errors appear, the coffee batch is at risk of being rejected, causing losses to the farm. Some defects such as mold and pollution not only affect the taste and value of the seeds but also cause harmful health effects for consumers. Join 43 Factory Coffee Roaster to discover some common mistakes of green coffee and how manufacturers prevent them!


Common defects of green coffee beans, causes and solutions


Almost all coffee varieties do not have high resistance to pests and diseases, making the fruit susceptible to harmful bacteria. Furthermore, if exposed directly to external factors such as high temperature, humidity, sunlight, etc., coffee can quickly oxidize, creating defects. Some common errors often seen with identifying signs include:


1. Full Black & Partial Black Beans


Black-contaminated coffee is easy to recognize through external senses. The seeds will be black or brown and completely or partially wrinkled, with cracks between the seeds widening. They will cause coffee to have an unpleasant odor similar to a phenolic, fishy smell. At certain times there may even be a fermented taste.

The causes of black coffee are insufficient nutrients, lack of water during growth, undeveloped fruit or fungal disease. In addition, if the coffee cherries are over-fermented or overripe, or if fallen cherries are used for processing, it can also lead to black coffee.

To avoid black coffee, farmers need to ensure proper nutrition and watering of the plants while controlling the development of fungal diseases, harvesting while the cherries are still on the tree and being careful during the fermentation process.

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2. Sour Coffee (Full Sour & Partial Sour Beans)


Sour coffee will be light brown, red or yellow. The outer shell may be reddish brown. When scratched, the seeds can give off a vinegar smell. Coffee with this error often has a sour, grassy flavor.

Common causes of sour-tasting coffee can include harvesting too late, overripe berries, over-fermentation, contaminated water used in processing,  or storage with too much humidity.

To avoid sour coffee, manufacturers need to accurately calculate the time of harvest, process it right after picking if it is wet or semi-wet, and always use clean water when processing.


3. Broken or Crushed Beans


Broken seeds are a common defect and are easiest to detect because the seeds are no longer intact but are broken and cracked into many pieces. This causes during the roasting process, heat cannot be transmitted evenly through the beans. The metabolic reactions take place unevenly, causing the flavor to be imbalanced. In addition, broken seeds also create conditions for bacteria to easily penetrate, accelerating the decomposition process, causing the seeds to become infected with fungi and spoil faster.

This defect can be caused by machinery during processing when peeling, removing the pulp, drying and milling. Furthermore, if unripe coffee is picked, poor humidity during storage will also cause the beans to break easily.

Manufacturers can limit this error by cleaning machines regularly, paying attention to ripeness and humidity when harvesting, storing and carefully classifying broken beans to avoid contaminating the entire batch of coffee.


4. Unripe coffee (Quakers)


This defect occurs when harvesting smaller, unripe coffee beans at low density. When completely peeled and in the green coffee state, they are difficult to detect later. However, you can identify them after roasting through color because unripe coffee will have a lighter color. If you use unripe coffee, the taste will smell like paper.

The underripe coffee bug or Quakers is often caused by plant malnutrition, drought, poor picking techniques, harvesting when the coffee is still green, or coffee leaf rust.

To avoid Quakers, coffee needs to be hand-picked by skilled workers. They have enough experience through size, color, and juiciness to predict whether the seeds are ripe enough to harvest.


5. Insect Damage


With this defect, the surface of the fruit or seed will have small holes. Depending on the type of insect pest, a cup of coffee may have a light smell or a sour taste.

The cause is due to many insects eating coffee cherries while the coffee is still on the tree or during storage. The most common of which is the coffee berry borer. It is also possible that because there are many holes, mold can start to grow.

The way to prevent coffee from being bitten by insects is to regularly check the growing area and use insect traps or insecticide preparations.


6. Fungus or Mold


Coffee infected with fungus can cause white, yellow, gray or red spores to appear on the beans, creating a musty, earthy flavor. Not only that, some types of mold can cause poisoning, affecting your health.

The main cause of coffee fungus infection is related to humidity. For example, fermentation time is too long, interruption during drying, preserving beans with high moisture content…

Manufacturers must exercise extreme caution when using natural or honey processing methods. Only process natural coffee and honey under suitable climatic conditions or technology. Remove seeds damaged by insects/machines and sort them carefully to avoid breakage or spread of mold.


7. Potato Defect


Potato defects in coffee are very difficult to recognize. You can only tell when roasted coffee has the taste of raw potatoes.

The cause is the Antestia beetle that often appears in East Africa. They create small holes, allowing bacteria to penetrate, causing the smell of potatoes.

Producers can guard against the possibility of this insect infestation by regularly inspecting crops for infestation and taking appropriate pest prevention measures.

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How to solve the defects of green coffee beans


For manufacturers, following strict quality control procedures to eliminate defects can be costly. Coffee requires a lot of effort and meticulousness from cultivating, harvesting, and classifying to mechanism, transportation, and preservation. However, specialty coffee farmers take this very seriously. Manufacturers and experts have researched specific techniques for each coffee defect and proposed measures to thoroughly eliminate defects in this specialty coffee:

The first is to choose the best production methods such as agroforestry and bioenergy to best protect crops. These methods are based on sustainable science, creating a natural, harmonious environment for plants to grow and avoiding harmful insects through their natural enemies.

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During farming, the farm needs to control humidity, nutrients, and irrigation systems for timely replenishment. Regularly check the condition of the tree, prune branches to keep the growing area airy and clean, and prevent pests from developing.

In addition, when harvesting, farmers need to pay attention to picking coffee cherries that are fully ripe and undamaged. When picked, coffee cherries must be washed, sorted and processed quickly to avoid damage. After preliminary processing and drying, coffee should be carefully stored at appropriate temperature and humidity, away from light and toxic substances.

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Coffee defects can appear throughout the entire process of creating the product. Manufacturers must always emphasize meticulousness in every product creation process to produce clean, delicious batches of coffee. If you want to experience specialty coffee beans from famous farms that meet international standards, visit XLIII Coffee – the brand developed from the predecessor 43 Factory Coffee Roaster.

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