Updated: September 2026.
What Is Coffee Hulling?
Coffee hulling (also called dry milling or threshing) is the removal of the parchment, the dry husk that surrounds the bean, to obtain green coffee. It is done at a hulling mill, starting from dry parchment coffee, and includes cleaning, hulling and grading the beans before roasting or export. In Colombia, 90-94 kg (198-207 lb) of dry parchment coffee yields about 70 kg (154 lb) of excelso green coffee; that "yield factor" is the measure of a lot's quality.
On every coffee bean's journey to your cup, there is a crucial step that determines the quality, character and potential of each harvest: hulling. At Green Hills Coffee, we don't just understand the importance of this process — we have refined it into an art. As an integral part of the coffee process from plant to perfect cup, hulling is where tradition meets technology to create world-class Colombian specialty coffee.
Hulling: The Decisive Moment for Coffee
Hulling is much more than a simple mechanical process. It is the moment the coffee bean sheds its parchment and reveals its true character. At our coffee hulling mill in Medellín, coffee arrives as dry parchment and leaves as green coffee, ready to roast or export. This process defines the uniformity, cleanliness and aromatic potential each bean will carry into roasting at our facilities as coffee roasters in Medellín, Colombia.
At Green Hills Coffee, we know that exceptional hulling can take a good coffee to extraordinary. That's why we have developed a process that respects and enhances the unique characteristics of each origin. Every bean that arrives from our coffee farms in Colombia goes through this careful process, which determines the final quality you'll enjoy in every cup of authentic Colombian coffee.
Hulling is especially important for different processing methods. Our natural specialty coffee requires specific techniques to preserve its fruity notes, while our honey specialty coffee needs careful handling to keep the mucilage residues that give it its distinctive character.
What Does the Coffee Hulling Process Involve?
Hulling turns dry parchment coffee into green coffee ready to roast or export. It generally follows these six steps:
- Receiving and sampling: the dry parchment coffee is weighed, its moisture is checked to be between 10% and 12%, and a sample is taken to calculate the lot's yield.
- Pre-cleaning: stones, sticks, dust and other impurities that arrive with the beans are removed.
- Hulling: the huller removes the parchment by friction, and an aspiration system separates the husk from the beans.
- Size grading: the beans pass through screens with meshes of different sizes that sort them by size.
- Density and color sorting: gravity tables and electronic color sorters remove light, broken or defective beans.
- Bagging: the green coffee is packed into sacks, ready for roasting or export.
From parchment to green coffee: what changes during hulling
| Characteristic | Dry parchment coffee | Green or excelso coffee |
|---|---|---|
| State | Bean inside its husk (parchment) | Clean, graded bean without parchment |
| Moisture | 10-12% | 10-12% (unchanged) |
| Weight | 90-94 kg | About 70 kg (yield factor) |
| Use | Storage and sale by the farmer | Roasting or export |
| Shelf life | Longer: the parchment protects the bean | Shorter; best roasted within a few months |
The yield factor (kilos of dry parchment needed to obtain 70 kg of excelso coffee) is the indicator used by the Colombian Coffee Growers Federation (FNC) to set the quality and price of coffee in Colombia.
What Sets Us Apart as a Hulling Mill
1. Cutting-edge technology with an artisanal touch
Our facilities combine the precision of state-of-the-art equipment with the irreplaceable experience of our master millers. Each lot goes through an electronic sorting system that analyzes size, density and color, backed by expert visual inspection.
This combination of technology and human expertise is what allows us to maintain the quality standards of our products, from Tradition specialty coffee to our exclusive Gold specialty coffee.
2. Full traceability
From the moment we receive parchment coffee until it leaves as green coffee, we keep meticulous records of every lot. Our system lets us trace each sack back to its farm of origin, variety and processing method, ensuring complete transparency.
This traceability is essential to maintaining the quality and specific characteristics that let you uncover the secrets of specialty coffee and identify an excellent coffee in every cup.
3. Precision grading
Our process separates beans into more than 12 categories by size, density and quality. This grading creates extremely uniform lots that make roasting consistent and let each coffee express its character to the full.
That precision is what allows every product in our line, from Bronze specialty coffee to Silver specialty coffee, to keep the consistent characteristics coffee lovers expect lot after lot.
4. Commitment to sustainability
Our hulling process is designed to minimize environmental impact. We reuse the parchment as fuel for our dryers, treat all our wastewater and have cut our energy consumption by 30% over the last three years.
This commitment extends to our entire process, including our vacuum packaging, which preserves the magic of specialty coffee while minimizing waste.
Why the Best Coffees Pass Through Our Hands
Green Hills Coffee's reputation as an elite hulling mill is no accident. The most demanding roasters trust our hulling service because they know that:
- We preserve the identity of each origin and process
- We guarantee uniformity lot after lot, year after year
- We remove defects that could compromise the cup
- We optimize the potential of every bean for roasting
- We document every step of the process meticulously
Specialized processing by coffee type
Our hulling process is adapted to each processing method:
For natural coffee
Natural coffee requires special techniques to preserve the fruity notes that develop during drying with the full cherry.
For honey coffee
Honey coffee needs delicate handling to keep the mucilage residues that give it its characteristic sweetness.
For washed coffee
Traditional washed coffee requires techniques that preserve the clarity and bright acidity typical of this method.
The Result: Exceptional Coffees
The true proof of our work is the coffee we process. Our clients have won multiple awards in international competitions, and their coffees appear on the menus of some of the world's most prestigious coffee shops.
Internationally recognized quality
The coffees that pass through our mill are also available for you to enjoy at home:
- Natural Specialty Coffee - Where fruity notes shine thanks to our process
- Honey Specialty Coffee - Sweetness perfectly preserved
- Tradition Specialty Coffee - Exemplary balance and consistency
An experience in every cup
When a coffee passes through Green Hills Coffee's mill, it gains the mark of quality, consistency and excellence that only a process refined over generations can give. You can taste that quality with any brewing method you choose:
- Espresso - Where bean uniformity is crucial
- V60 - Which reveals the clarity achieved in hulling
- Chemex - Ideal for appreciating a clean bean
- French press - Where the body and character of the bean come through fully
Benefits of Our Hulling Process
For coffee drinkers
The benefits of Colombian specialty coffee are preserved and enhanced by our hulling process:
- Consistency in every cup - Removing defects that could alter the flavor
- Preserved antioxidants - Careful handling that keeps beneficial compounds intact
- Even roasting - Graded beans allow more precise roasting
- Pure expression of terroir - Origin characteristics preserved intact
For baristas and enthusiasts
Coffee professionals value our work because it offers:
- Easier brewing - Uniform beans need fewer adjustments
- Predictability - Consistent results every time
- Versatility - Adapts to different types of coffee according to their preparation
Exploring Our Quality
Recipes to taste the difference
To fully experience the results of our process, explore our 25 coffee recipes. Each one lets you appreciate a different side of the quality achieved in hulling.
Special experiences
Try drinks that showcase the quality of the coffee:
- The perfect mocha - Where the quality of the base coffee is essential
- Affogato - A sweet pairing that calls for exceptional coffee
- Americano - Where bean uniformity is obvious
Coffee Hulling FAQ
What is coffee hulling?
It is the removal of the parchment, the dry husk that surrounds the bean, to obtain green coffee. It is done at a hulling mill from dry parchment coffee and includes cleaning, hulling and grading the beans before roasting or export.
What does the hulling process involve?
It turns dry parchment coffee into green coffee in six steps: receiving and sampling, pre-cleaning, hulling, size grading, density and color sorting to remove defects, and bagging the green coffee.
How much green coffee do you get from a kilo of parchment?
About 750-780 g. In Colombia this is measured with the yield factor: the kilos of dry parchment needed to obtain 70 kg of excelso coffee, usually between 90 and 94. The lower the factor, the better the lot's quality.
When is coffee hulled?
Just before roasting or export, not right after harvest. The parchment protects the bean from moisture and oxidation, so coffee is stored as parchment and hulled in batches as needed.
What is the difference between hulling and pulping?
Pulping happens on the farm, right after the cherry is harvested: it removes the red skin and pulp and leaves the bean with its mucilage and parchment. Hulling happens weeks or months later, once the bean is dry: it removes the parchment and leaves green coffee.
Do you have a brand, a farm or a roastery and want to take your coffee to the next level? Find out how our coffee hulling service works and get in touch to get the most out of your harvest.
Green Hills Coffee: raising coffee quality, one bean at a time.
Written by the Green Hills Coffee team, specialty coffee growers, millers and roasters in Itagüí, Antioquia.
