Coffee is one of the world’s most popular drinks, enjoyed by millions of people every day. At its heart, coffee is a brewed beverage made from the roasted seeds of the coffee plant. These seeds, which we know as coffee beans, are found inside the fruit of the coffee tree, known as a coffee cherry.

Although we often call them beans, coffee beans aren’t actually beans at all—they’re the seeds of the coffee cherry. Once harvested, the fruit is removed, the seeds are processed and dried, before being roasted to develop the rich aromas and flavours that make coffee so distinctive.

Today, coffee is grown in more than 70 countries around the world, with each region producing beans that have their own unique flavour characteristics. Factors such as altitude, climate, soil and processing methods all influence the final taste in your cup, which is why no two coffees are exactly the same.

At Acorns Coffee, we source high-quality single origin coffees from around the world before roasting them in small batches in Hampshire. Roasting allows us to bring out each coffee’s natural character, whether that’s rich chocolate notes, bright citrus flavours or delicate floral aromas.

Whether you enjoy a smooth espresso, a cafetière at breakfast or a carefully brewed V60, every cup begins its journey as a small seed growing on a coffee tree.

Key Facts

• Coffee comes from the seeds of the coffee cherry.
• Coffee trees grow in tropical regions around the world.
• Every coffee bean is roasted before it can be brewed.
• Flavour is influenced by where the coffee is grown, how it’s processed and how it’s roasted.
• The two most common coffee species are Arabica and Robusta.

Did You Know?

A coffee tree can take three to four years before producing its first harvest, and a healthy tree can continue producing coffee cherries for more than 20 years.

Related questions

• Where does coffee come from?
• What is a coffee cherry?
• What is the Coffee Belt?
• What is Arabica coffee?
• What is Robusta coffee?
• How is coffee grown?

Coffee grows in some of the world’s most beautiful tropical regions, where warm temperatures, rich soils and regular rainfall create the ideal conditions for coffee trees to thrive. Today, coffee is produced in more than 70 countries, but the vast majority is grown within a narrow band around the Equator known as the Coffee Belt.

Some of the world’s most famous coffee-producing countries include Brazil, Colombia, Ethiopia, Guatemala, Kenya, Peru, Indonesia, Mexico and Rwanda. Each country, and often each individual farm, produces coffee with its own distinctive flavour profile.

The taste of coffee is influenced by many factors, including altitude, rainfall, soil composition, climate and the way the coffee is processed after harvest. That’s why a naturally processed Ethiopian coffee can taste bright and fruity, while a Brazilian coffee is often known for its smooth chocolate and nut flavours.

At Acorns Coffee, we source carefully selected single origin coffees from across the Coffee Belt, allowing you to explore the unique flavours each growing region has to offer.

Key Facts

• Coffee is grown in over 70 countries.
• Most coffee grows between the Tropic of Cancer and the Tropic of Capricorn.
• Brazil is the world’s largest coffee producer.
• Every coffee-growing region produces its own distinctive flavours.
• Climate, altitude and soil all influence the taste of coffee.

Despite what many people think, coffee doesn’t begin life as a bean—it begins as a fruit.

A coffee cherry is the fruit that grows on the coffee tree. As it ripens, it changes from green to bright red, although some varieties can ripen to yellow or even orange. Farmers carefully harvest these ripe cherries by hand or machine, depending on the farm and terrain.

Inside each coffee cherry are usually two seeds. These seeds are what we know as coffee beans. Before they can be roasted, the beans must first be removed from the fruit, cleaned and dried using one of several processing methods.

The quality of the coffee cherry is incredibly important. Healthy trees, ideal growing conditions and harvesting only fully ripe cherries all contribute to producing exceptional coffee. Picking cherries too early or too late can have a noticeable impact on the flavour of the finished cup.

Interestingly, not every cherry contains two beans. Occasionally, a cherry develops just one rounded bean, known as a Peaberry. These are relatively rare and are often separated during processing because they roast slightly differently.

At Acorns Coffee, every coffee we roast started life as a carefully grown coffee cherry on a farm somewhere within the Coffee Belt, before beginning its journey through processing, roasting and finally into your cup.

Key Facts

• Coffee cherries are the fruit of the coffee tree.
• Most ripe cherries are deep red when ready to harvest.
• Each cherry usually contains two coffee beans.
• The fruit is removed before the beans are dried and roasted.
• Around 5–10% of coffee cherries produce a single Peaberry instead of two beans.

Did You Know?

Unlike many crops, coffee cherries don’t all ripen at the same time. On many specialty coffee farms, pickers return to the same trees several times during the harvest season, selecting only the ripest cherries each time. This careful hand-picking is one reason why high-quality specialty coffee takes so much time and skill to produce.

Growing coffee is a slow process that requires patience, expertise and the right environment. Coffee trees thrive in warm tropical climates, where they receive plenty of rainfall, fertile soil and consistent temperatures throughout the year. These ideal conditions are found within the Coffee Belt, which stretches around the Equator.

Most coffee begins life in a nursery, where young seedlings are carefully nurtured before being transplanted into coffee plantations. Depending on the variety, it can take three to four years before a coffee tree produces its first harvest of cherries.

Once mature, the trees burst into life with delicate white flowers, often described as smelling similar to jasmine. These blossoms last only a few days before developing into small green cherries, which slowly ripen over the following months. As they mature, the cherries turn bright red, signalling they’re ready to be harvested.

Unlike many crops, coffee cherries rarely ripen all at once. On specialty coffee farms, skilled pickers often return to the same trees several times during the harvest season, selecting only the ripest cherries by hand. This careful harvesting helps ensure only the highest quality fruit continues its journey towards becoming great coffee.

A healthy coffee tree can continue producing cherries for 20 to 30 years, although many are capable of producing for much longer when well cared for. Throughout its life, the tree requires ongoing pruning, fertilisation and protection from pests and changing weather conditions.

At Acorns Coffee, every coffee we roast starts with the dedication and expertise of farmers who spend years caring for their trees before the beans ever reach our roastery.

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Key Facts

• Coffee trees take 3–4 years to produce their first harvest.
• Coffee plants grow best in tropical climates with consistent rainfall and temperatures.
• White coffee blossoms appear before cherries develop.
• Cherries often ripen at different times, making multiple harvests necessary.
• A healthy coffee tree can produce coffee for 20–30 years or more.

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Did You Know?

Each coffee tree produces only a relatively small amount of coffee each year. On average, a single mature tree yields enough cherries to produce around 0.5–1 kg of roasted coffee, depending on the variety, growing conditions and processing methods. That’s why every bag of specialty coffee represents months of careful work by farmers long before it reaches the roastery.

Arabica, or Coffea arabica, is one of the most important species of coffee plant in the world. It accounts for a large proportion of the coffee produced globally and is particularly important within the specialty coffee industry.

Arabica coffee is believed to have originated in the highlands of Ethiopia, where the species developed naturally before being cultivated and spread to other parts of the world.

Arabica plants generally prefer higher elevations, cooler temperatures and stable growing conditions. They can be more demanding to grow than other coffee species, but when carefully cultivated they can produce remarkably complex and distinctive coffees.

What does Arabica coffee taste like?

There isn’t one single “Arabica flavour”.

That’s one of the most interesting things about coffee.

Arabica coffees can be:

• Fruity and vibrant
• Floral and delicate
• Sweet and caramel-like
• Chocolatey and nutty
• Bright and acidic
• Smooth and balanced

The final flavour depends on far more than the species itself. Variety, altitude, climate, soil, farming, processing and roasting all play a role.

This is why an Ethiopian Arabica can taste completely different from a Brazilian or Colombian Arabica, despite technically being the same coffee species.

Why is Arabica considered special?

Arabica plants generally produce coffee with a greater range of delicate and complex flavours, which is one reason they’re so highly valued in specialty coffee.

However, Arabica doesn’t automatically mean better coffee.

A poorly grown or poorly processed Arabica can produce a disappointing cup, while a carefully grown and processed Robusta can be exceptional in its own right.

At Acorns Coffee, we don’t choose a coffee simply because it is Arabica. We look at its origin, variety, farming, processing and flavour potential before deciding whether it’s something we want to roast.

Arabica at Acorns

Many of the single origin coffees we roast at Acorns are Arabica coffees, including coffees from Colombia, Ethiopia, Guatemala, Kenya, Rwanda and Brazil.

Exploring these coffees side by side is a great way to understand just how diverse Arabica can be.

A Colombian coffee might give you smooth toffee and chocolate, while an Ethiopian coffee can be bright, floral and fruit-forward. The species is the same — but the environment and journey from farm to cup are very different.

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Key Facts

• Arabica’s scientific name is Coffea arabica.
• It originated in Ethiopia.
• Arabica generally prefers higher elevations and cooler growing conditions.
• It can produce highly complex and diverse flavours.
• Arabica doesn’t automatically mean better quality.
• Growing conditions, processing and roasting all influence the final cup.

Did You Know?

Arabica coffee contains less caffeine than Robusta. This isn’t because it is deliberately grown to be lower in caffeine — it’s simply a natural difference between the two species.

Robusta, commonly known as Coffea canephora, is one of the world’s most important coffee species. While Arabica tends to dominate specialty coffee, Robusta makes up a significant proportion of global coffee production and plays an important role in espresso, instant coffee and blends.

Robusta is native to central and western sub-Saharan Africa and is now grown in many tropical coffee-producing countries, particularly in Africa, Southeast Asia and parts of South America.

The name “Robusta” is fitting. The plant is generally hardier and more resistant to disease and pests than Arabica, and it can grow successfully in warmer conditions and at lower elevations.

What does Robusta coffee taste like?

Robusta has a very different flavour profile from Arabica.

It can often have:

• Strong, powerful flavours
• Earthy or woody characteristics
• Nutty and chocolate notes
• A heavier body
• More pronounced bitterness
• A long, intense finish

However, just like Arabica, there is no single Robusta flavour. Growing conditions, variety, farming, processing and roasting all have a significant influence on the finished coffee.

High-quality fine Robusta can be surprisingly sweet, clean and complex — very different from the harsh, bitter Robusta that has sometimes given the species its reputation.

Why does Robusta contain more caffeine?

One of Robusta’s most noticeable differences is its caffeine content.

Robusta naturally contains considerably more caffeine than Arabica, which the plant uses as part of its natural defence against insects and pests.

This extra caffeine, combined with Robusta’s heavier body, can make it particularly useful in espresso blends, where it can contribute intensity, body and a rich crema.

How is Robusta grown?

Robusta is generally more tolerant of heat, lower elevations and challenging growing conditions than Arabica.

It can produce good yields in environments where Arabica would struggle, making it an important crop for farmers in warmer regions.

The plant can also be more resistant to some of the diseases and pests that affect coffee production.

But being hardy doesn’t mean producing ordinary coffee.

As the specialty coffee industry has developed, more attention has been given to fine Robusta, with producers experimenting with varieties, farming techniques and careful processing to reveal the quality and complexity that Robusta can offer.

🇻🇳 Robusta at Acorns

We currently roast Vietnam Son La Robusta, giving us a great opportunity to experience Robusta as a single origin coffee rather than simply as part of a commercial blend.

Vietnam is the world’s leading producer of Robusta, and the Son La region in northern Vietnam is becoming increasingly interesting for specialty coffee.

Our Son La demonstrates why it’s worth looking beyond the traditional Arabica-versus-Robusta debate. It has the strength and character you’d expect from Robusta, but its origin and careful roasting reveal a much more interesting side of the species.

The Coffee Belt is the region of the world where almost all coffee is grown. Rather than being one specific place, it’s a band of tropical countries that sits between the Tropic of Cancer and the Tropic of Capricorn, stretching around the Equator.

This part of the world provides the warm temperatures, seasonal rainfall and fertile soils that coffee trees need to thrive. Outside of the Coffee Belt, climates are generally too cold or too dry for commercial coffee production.

More than 70 countries grow coffee within this region, including Brazil, Colombia, Ethiopia, Guatemala, Kenya, Peru, Indonesia, Mexico and Vietnam. Each country, and often each individual farm, has its own unique combination of altitude, climate, soil and growing conditions, giving every coffee its own distinctive character.

For example, coffees grown at higher elevations often develop brighter acidity and more complex fruit flavours, while lower-grown coffees tend to produce richer, smoother and more chocolate-forward cups. That’s one of the reasons coffee from different parts of the world can taste so dramatically different.

At Acorns Coffee, we source single origin coffees from across the Coffee Belt, allowing us to showcase the incredible diversity of flavour that coffee-growing regions have to offer.

Key Facts

• The Coffee Belt circles the Earth around the Equator.
• It lies between the Tropic of Cancer and the Tropic of Capricorn.
• More than 70 countries grow coffee within the Coffee Belt.
• Climate, altitude and soil all influence flavour.
• Every coffee-growing country has its own unique characteristics.

Did You Know?

Although Brazil is the world’s largest coffee producer, coffee was first discovered in Ethiopia, where legend tells of a goat herder named Kaldi noticing his goats became unusually energetic after eating coffee cherries. While the story can’t be confirmed, Ethiopia is widely recognised as the birthplace of Arabica coffee.

Altitude is one of the most important factors influencing how coffee develops and, ultimately, how it tastes in your cup.

Coffee plants generally grow best at higher elevations in tropical regions, where cooler temperatures cause the coffee cherries to ripen more slowly. This extended maturation gives the developing coffee seed more time to build sugars and complex flavour compounds.

But higher altitude doesn’t automatically mean better coffee. The ideal elevation depends on the coffee variety, climate, soil and farming practices. It’s the combination of these factors that makes each growing region unique.

What happens at higher altitude?

As elevation increases, temperatures generally become cooler. Coffee cherries take longer to mature, and this slower development can contribute to coffees with:

• Brighter acidity
• Greater sweetness
• More complex flavours
• Floral and fruity characteristics
• A lighter, more vibrant character

Lower-altitude coffees often mature more quickly and can produce fuller-bodied, smoother and more chocolate or nut-forward flavours.

This is one reason coffees from different parts of the world can taste so dramatically different, even when they are brewed in exactly the same way.

Altitude in our coffees

You can see the influence of growing conditions across the coffees we roast at Acorns.

Colombia Finca Sofia, for example, is grown at altitude in the Colombian Andes, contributing to its smooth, balanced character and notes of toffee and chocolate.

Our Ethiopia Yirgacheffe comes from the highlands of Ethiopia, where altitude and growing conditions help produce the bright, aromatic and often floral and fruity characteristics associated with Ethiopian coffee.

These differences are part of what makes exploring single origin coffee so fascinating. The coffee isn’t simply from a country — its flavour is a reflection of the particular environment in which it was grown.

It’s more than just altitude

It’s tempting to think of coffee quality as a simple equation:

Higher = better

But that’s not really how coffee works.

Altitude interacts with temperature, rainfall, sunlight, soil, coffee variety, farming practices and processing. Two farms at exactly the same elevation can produce completely different coffees.

That’s why we look at the whole story behind a coffee when selecting what to roast at Acorns.

Key Facts

• Higher elevations generally mean cooler temperatures.
• Cooler temperatures can slow cherry maturation.
• Slower maturation can allow more time for sugars and flavour compounds to develop.
• Altitude can influence acidity, sweetness, body and complexity.
• Higher altitude doesn’t automatically mean better coffee.

Did You Know?

Altitude is usually measured in metres above sea level, but elevation alone doesn’t tell the whole story. A coffee grown at 1,500 metres in one part of the world may experience very different temperatures, rainfall and sunlight from a coffee grown at the same elevation elsewhere.

Harvesting coffee is one of the most important stages in the journey from coffee tree to coffee cup. Once coffee cherries have ripened, they need to be carefully picked from the trees and collected before they can be processed.

Unlike many agricultural crops, coffee cherries don’t necessarily ripen at the same time. A single coffee tree can have green, yellow and fully ripe red cherries growing alongside each other. This makes harvesting high-quality coffee a careful and often labour-intensive process.

How are coffee cherries picked?

There are three main approaches to harvesting coffee: selective hand-picking, strip picking and mechanical harvesting.

Selective hand-picking

This is commonly used for specialty coffee and on farms where the terrain makes machinery difficult to use.

Pickers move through the coffee trees, selecting the ripe cherries while leaving unripe fruit to mature. They may return to the same trees several times during the harvest season.

It’s slow, demanding work, but it allows farmers to select fruit at the ideal stage of ripeness.

Strip picking

With strip picking, the cherries are removed from a branch in one movement, often by hand. Ripe and unripe cherries can therefore be collected together and separated later.

This method can be quicker than selective picking and is used in some coffee-producing regions.

Mechanical harvesting

On larger farms, particularly where the landscape allows it, specialised machines can remove cherries from the trees.

Mechanical harvesting can be much faster, but it can also collect cherries at different stages of ripeness. Further sorting is therefore often required before processing.

Why does harvesting matter?

The quality of the coffee can be affected before the beans have even left the farm.

Overripe, underripe or damaged cherries can introduce unwanted flavours during processing. Careful harvesting helps ensure that the best fruit continues through the next stage of the journey.

This is particularly important for specialty coffee, where farmers and producers are trying to preserve the unique characteristics of a particular variety, farm and growing region.

Harvesting also requires an enormous amount of skill and effort. Behind every bag of coffee is a chain of people who have cared for the plants, monitored the crop and spent hours selecting and collecting the fruit.

At Acorns Coffee, we think that part of the story is worth knowing.

When is coffee harvested?

Coffee harvest seasons vary depending on the country, climate, altitude and local growing conditions.

Some regions have one main harvest each year, while others can have more than one flowering and harvesting period.

Because coffee is grown across many different parts of the world, there isn’t one global “coffee harvest season”. This is one reason coffee from different origins becomes available at different times throughout the year.

Key Facts

• Coffee cherries are harvested once they reach the appropriate stage of ripeness.
• Selective hand-picking allows farmers to choose ripe cherries individually.
• Strip picking removes many cherries from a branch at once.
• Mechanical harvesting is used on some larger farms.
• Harvesting carefully can help protect the quality and flavour of the finished coffee.
• Harvest seasons vary around the world.

Did You Know?

Coffee pickers can carry baskets or containers with them as they work, gradually filling them with cherries before transferring the fruit into larger collection sacks or containers.

That means a coffee bean that eventually ends up in your cup may have been individually selected by hand months before it reaches the roastery.

Once coffee cherries have been harvested, the journey is far from over. Before the coffee can be roasted, the fruit must be removed from the seeds inside, and those seeds need to be processed and dried carefully.

This stage is known as coffee processing, and it can have a huge influence on how the finished coffee tastes.

The way a coffee is processed can help determine whether it develops a clean and delicate character, or something much more fruity, sweet and fermented.

 From Cherry to Green Coffee

After harvesting, coffee cherries are usually taken to a processing facility on or near the farm. The cherries need to be processed relatively quickly to prevent unwanted fermentation or deterioration.

There are several different ways this can happen, but the three traditional methods you’ll hear about most often are:

Washed Process

The coffee fruit is removed from the seed, usually using water and mechanical equipment. The beans are then fermented to remove remaining fruit before being thoroughly washed and dried.

Washed coffees are often associated with clean, bright and precise flavours, allowing characteristics of the coffee’s variety and growing region to shine through.

Natural Process

With natural processing, the whole coffee cherry is dried with the fruit still surrounding the seeds.

As the cherry dries, the fruit naturally interacts with the coffee seeds, contributing sugars and flavour compounds. Once sufficiently dry, the dried fruit is removed.

Natural coffees can be particularly fruity, sweet and full-bodied, although the exact character depends on the coffee and how it was processed.

Honey Process

Despite the name, no honey is added.

Instead, the skin of the coffee cherry is removed while some of the sticky fruit, known as mucilage, remains attached to the seed during drying.

Honey processing sits somewhere between washed and natural processing, and can produce coffees with sweetness, body and fruit character, while still retaining a relatively clean cup.

Drying the Coffee

Whichever processing method is used, the coffee eventually needs to be dried to a safe moisture level.

This can be done using:

• Raised drying beds
• Patios
• Mechanical dryers
• A combination of natural and mechanical drying

Drying is an incredibly important part of coffee production. If coffee dries too quickly, too slowly or unevenly, the quality can suffer.

Once dried, the coffee is usually hulled to remove the remaining outer layers, leaving what we recognise as green coffee beans.

These green beans can then be sorted, graded, stored and eventually transported to roasters around the world.

Why Does Processing Matter?

This is where coffee starts to become particularly fascinating.

Two coffees grown on neighbouring farms could potentially be the same variety, grown at a similar altitude, but taste completely different because they were processed differently.

Processing doesn’t simply happen after the coffee is grown — it becomes part of the coffee’s identity.

That’s why you’ll often see the processing method listed alongside the country, farm, variety and altitude when buying specialty coffee.

At Acorns Coffee, we pay close attention to how each coffee has been processed because it helps us understand what we’re working with when the green beans arrive at the roastery.

Key Facts

• Coffee cherries need to be processed after harvesting.
• Processing removes the fruit from the coffee seed.
• Washed, natural and honey are three common processing methods.
• Drying must be carefully controlled to protect quality.
• Once processed and dried, coffee becomes green coffee ready for export and roasting.
• Processing can have a significant influence on the flavour of the finished coffee.

Did You Know?

Coffee beans are actually green before they are roasted. The familiar brown colour, aroma and flavours we associate with coffee develop later during the roasting process.

What is Green Coffee?

When you hear the words green coffee, you might imagine a particular variety of coffee or a different type of bean. In reality, green coffee is simply coffee that has not yet been roasted.

After coffee cherries are harvested, processed and dried, the seeds inside them become what the coffee industry calls green coffee beans. They are the raw material that roasters buy and transform into the familiar brown beans we use to make coffee.

What does green coffee look like?

Green coffee beans are usually pale green, yellow-green or even blue-green in colour, depending on the coffee’s origin, variety, processing method and age.

They are also much harder and denser than roasted coffee beans. If you were to grind a green coffee bean, you wouldn’t get the familiar coffee aroma or flavour we’re used to — those develop largely during roasting.

Where does green coffee come from?

Green coffee begins its journey on coffee farms around the world.

Once the cherries have been harvested and processed, the dried seeds are prepared for export. They may be graded and sorted according to factors such as size, density, moisture, defects, processing method and cup quality before being packed and shipped to coffee roasters.

This is where origin becomes really important.

A green coffee from Brazil can have very different characteristics from one grown in Ethiopia, Colombia or Indonesia. Variety, altitude, climate, soil, processing and farming practices all contribute to the potential flavour of the finished coffee.

Why can’t we just brew green coffee?

Technically, green coffee can be prepared in various ways, but it isn’t what we normally mean when we talk about coffee.

Roasting changes everything.

During roasting, heat causes a series of chemical reactions that transform the green seeds. Their colour changes, their structure becomes more brittle and they develop the aromas and flavours associated with roasted coffee.

Sweetness, caramelisation, toasted flavours, chocolate characteristics and many of the aromas we recognise as coffee are developed or transformed during this process.

For a coffee roaster, this is where things get particularly interesting: the green coffee contains the potential, but the roast helps determine how that potential ends up in your cup.

☕ Green coffee at Acorns

At Acorns, we buy coffee as green beans and roast it here in Hampshire in small batches.

That means every coffee we roast starts in this raw state. Before we even turn on the roaster, we’re already thinking about the coffee’s origin, variety, processing method, density and moisture — and how those characteristics might respond to heat.

The aim isn’t simply to make the beans brown. It’s to develop the best flavours that are already there.

And that’s where the next part of our journey begins…

🔥 Key Facts

• Green coffee = unroasted coffee beans.
• Green coffee is the seed found inside the coffee cherry.
• Its colour can range from pale green to yellow-green or blue-green.
• Green coffee is harder and denser than roasted coffee.
• Origin, variety, altitude and processing all influence its potential flavour.
• Roasting transforms green coffee into the aromatic brown beans we know.
• At Acorns, we roast our green coffee in small batches here in Hampshire.

Washed coffee is a coffee that has had the fruit of the coffee cherry removed from the seed before the coffee is dried. It is one of the most widely used processing methods in the world and is particularly common in specialty coffee.

The name comes from the use of water during the process, although there’s considerably more to it than simply washing coffee beans.

How is washed coffee made?

After ripe coffee cherries are harvested, the fruit is mechanically removed from the seeds using a machine called a depulper.

The beans are then covered in a sticky layer of fruit called mucilage. This needs to be removed before the coffee can be dried.

Traditionally, the coffee is placed in fermentation tanks, where naturally occurring microorganisms break down the remaining mucilage. Once fermentation is complete, the beans are thoroughly washed to remove the remaining material.

The beans are then dried, often on raised beds or patios, until they reach the appropriate moisture level.

At this stage, the coffee is still green coffee, protected by a parchment-like outer layer. It can then be hulled, graded and prepared for export to roasters.

How does washed processing affect flavour?

Because most of the coffee cherry is removed before drying, washed processing tends to allow the characteristics of the coffee variety and growing environment to come through particularly clearly.

Washed coffees are often associated with:

• Clean, clear flavours
• Bright acidity
• Floral or citrus characteristics
• A lighter, more defined body
• A distinctive sense of origin

However, processing isn’t a flavour recipe. A washed Ethiopian coffee won’t necessarily taste like another washed Ethiopian coffee.

Variety, altitude, climate, soil, harvesting and roasting all contribute to the final cup.

🇨🇴 Washed coffee at Acorns

Our Colombia Finca Sofia is a great example of a washed coffee.

The coffee is grown in Colombia and processed using the washed method before making its way to our roastery.

When we roast and brew it, we get a coffee that is smooth, velvety and balanced, with flavours of toffee and chocolate.

It’s a good example of why we don’t think of processing methods as simply being “good” or “bad”. Instead, processing is one part of the story that helps explain why a particular coffee tastes the way it does.

Washed vs Natural

The simplest way to understand the difference is:

Washed:

🍒 Fruit removed → 💧 fermented & washed → ☀️ dried

Natural:

🍒 Whole cherry → ☀️ dried with fruit → 🫘 fruit removed

Neither method is inherently better. They simply create different opportunities for the coffee to develop its character.

Key Facts

• Washed coffee has its fruit removed before drying.
• Fermentation helps remove the remaining mucilage.
• Water is used to clean the coffee before drying.
• Washed coffees are often clean and clearly defined in flavour.
• Processing is only one of many factors that influence taste.

Did You Know?

The fermentation stage has to be carefully controlled. If coffee is fermented for too long, or under unsuitable conditions, unwanted flavours can develop. Experienced producers monitor factors such as time, temperature and the condition of the coffee throughout the process.

What is Natural Processed Coffee?

Natural processing is one of the oldest and most traditional ways of processing coffee. Unlike washed coffee, where the fruit is removed from the coffee seed before drying, natural processing allows the whole coffee cherry to dry around the seed.

This simple difference can have a significant influence on the flavour of the finished coffee.

How is natural processed coffee made?

After ripe coffee cherries are harvested, they are carefully sorted to remove unripe, damaged or overripe fruit.

Instead of removing the skin and fruit, the whole cherry is placed out to dry, often on raised beds or patios.

As the cherries dry, the fruit gradually shrinks around the coffee seeds inside. The sugars and other compounds in the fruit interact with the developing coffee, contributing to the character of the finished bean.

Producers carefully turn the cherries during drying to encourage even airflow and prevent unwanted mould or fermentation. Depending on the climate and conditions, drying can take several weeks.

Once the cherries have dried sufficiently, the dried fruit and outer layers are mechanically removed, leaving the green coffee bean ready for sorting, grading and eventually roasting.

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How does natural processing affect flavour?

Natural processing is often associated with coffees that have more pronounced fruitiness, sweetness and body.

You might find flavours described as:

• 🍓 Berries and ripe fruit
• 🍑 Stone fruit
• 🍷 Wine-like or fermented notes
• 🍯 Rich sweetness
• 🌺 Floral characteristics
• ☕ A fuller body
  

However, natural processing doesn’t automatically make a coffee fruity.

The final flavour is influenced by the coffee variety, growing conditions, altitude, harvesting, drying conditions and roasting as well as the processing method itself.

That’s what makes comparing coffees so interesting. Processing is just one part of the story.

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Natural vs Washed Coffee

The easiest way to understand the difference is to look at when the coffee fruit is removed.

Washed coffee:

🍒 Cherry → 🫘 Fruit removed → 💧 Washed → ☀️ Dried

Natural coffee:

🍒 Whole cherry → ☀️ Dried with fruit → 🫘 Fruit removed

Because the fruit remains around the seed during drying, natural processing can create a very different flavour experience from a washed coffee.

Neither method is inherently better. They simply give producers different ways of expressing the characteristics of the coffee.

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Why is natural processing used?

Natural processing is particularly well suited to regions where water is scarce, because it requires considerably less water than traditional washed processing.

It is also strongly associated with countries such as Ethiopia and Brazil, where natural coffees have a long history.

For producers, however, natural processing requires careful control. Cherries need to be spread evenly, regularly turned and monitored throughout drying. Poorly managed drying can lead to unwanted flavours or spoilage.

When done well, natural processing can produce some of the most intensely aromatic, sweet and fruit-forward coffees in the world.

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From Natural Coffee to Acorns

Once naturally processed green coffee reaches our roastery, the processing journey isn’t finished from our perspective.

As roasters, we need to understand what the processing method has contributed to the coffee before deciding how to roast it.

A naturally processed coffee can behave differently in the roaster from a washed coffee, and our job is to develop the roast in a way that allows the coffee’s natural character to shine.

That’s one of the things we love about roasting single origin coffee: the farmer, the variety, the environment and the processing method have already created a story. Our job is to help reveal it.

And no better than our Brazil Santos Coffee, a superb dry processed coffee bean and such a favourite of ours, it’s the coffee we use at our coffee shop in Bordon, Hampshire, UK.

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Key Facts

• Natural processing dries the whole coffee cherry around the coffee seed.
• It generally uses less water than washed processing.
• Drying can take several weeks.
• Natural coffees are often associated with fruity, sweet and full-bodied flavours.
• Careful drying is essential to prevent unwanted fermentation or mould.
• Processing is only one factor influencing the final flavour of coffee.
  

Did You Know?

Natural processing is sometimes called “dry processing” because the coffee cherry is dried without first removing the fruit. Despite the name, the process requires a great deal of care — simply leaving cherries in the sun isn’t enough to produce high-quality coffee.

What is Honey Processed Coffee?

Despite its name, honey processed coffee doesn’t contain any honey.

Honey processing is a method of preparing coffee where the skin and some of the fruit are removed from the coffee cherry, but a sticky layer of natural fruit called mucilage is left on the coffee seed while it dries.

The result sits somewhere between the traditional washed and natural processing methods, creating another way for coffee producers to influence the flavour and character of their coffee.

🍯 How is honey processed coffee made?

After ripe coffee cherries are harvested, the outer skin and some of the fruit are removed using a machine called a depulper.

Unlike washed coffee, the sticky mucilage surrounding the seed isn’t completely removed.

The coffee seeds, still covered with this layer of fruit, are then spread out to dry on raised beds or patios. As they dry, the mucilage gradually dries onto the coffee seed.

Producers carefully turn the coffee throughout the drying process to encourage even drying and prevent unwanted fermentation or mould.

Once the coffee has reached the correct moisture level, the remaining dried layers are removed, leaving the green coffee ready to be sorted, graded and eventually roasted.

How does honey processing affect flavour?

Honey processing can produce a fascinating balance between the characteristics associated with washed and natural coffees.

Honey processed coffees are often described as having:

• 🍯 Increased sweetness
• 🍊 Fruity or citrus flavours
• ☕ Medium to full body
• 🌸 Floral characteristics
• ✨ A clean but rounded finish

However, there isn’t one specific “honey process flavour”.

The final cup depends on the amount of mucilage left on the bean, the drying conditions, the coffee variety, altitude, climate and many other factors.

What are yellow, red and black honey?

You may sometimes see honey coffees described as yellow honey, red honey or black honey.

These names generally refer to the amount of mucilage left on the coffee and the way the coffee is dried.

Yellow Honey

Less mucilage is generally left on the bean and the coffee tends to dry relatively quickly.

Red Honey

More mucilage is retained and drying is usually slower, allowing more interaction between the coffee and the fruit.

Black Honey

A greater amount of mucilage is retained and the coffee is dried very slowly and carefully.

These aren’t strict international standards, and producers can use the terms somewhat differently. They are best thought of as descriptions of the producer’s particular processing approach rather than completely separate processing methods.

Why choose honey processing?

Honey processing can offer producers an interesting middle ground.

Compared with natural processing, the coffee doesn’t spend the entire drying period surrounded by the whole cherry. Compared with washed processing, however, some of the fruit remains in contact with the coffee during drying.

It can therefore provide an opportunity to develop additional sweetness and body while retaining some of the clarity associated with washed coffees.

The method can also use less water than traditional washed processing, making it an interesting option in regions where water availability is an important consideration.

Washed vs Natural vs Honey

The simplest way to see the difference is:

Washed

🍒 Cherry

→ Fruit removed

→ 💧 Mucilage removed

→ ☀️ Dried

Honey

🍒 Cherry

→ Skin removed

→ 🍯 Some mucilage remains

→ ☀️ Dried

Natural

🍒 Whole cherry

→ ☀️ Dried with fruit

→ 🫘 Fruit removed

Three different approaches, each capable of producing a completely different expression of coffee.

From the Farm to Acorns

When a honey processed coffee arrives at our roastery, the processing method is one of the first things we look at when deciding how we want to roast it.

The producer has already made important decisions about how the coffee should develop. Our role as roasters is to understand those decisions and create a roast that allows the coffee’s sweetness, body and origin character to shine.

It’s another reason we love single origin coffee: every coffee has a story that starts long before the green beans reach our roaster.

Key Facts

• Honey processed coffee contains no actual honey.
• Some of the coffee cherry’s natural mucilage remains on the seed during drying.
• It sits between washed and natural processing.
• Honey coffees can be sweet, fruity and full-bodied.
• Yellow, red and black honey describe different approaches to drying and mucilage retention.
• The exact flavour depends on much more than processing alone.

Did You Know?

The word “honey” comes from the sticky, honey-like texture of the mucilage left on the coffee seed — not from anything added during processing.

What is Wet-Hulled Coffee (Giling Basah)?

Wet-hulling, known locally as Giling Basah, is a distinctive coffee processing method most strongly associated with Indonesia, particularly the islands of Sumatra and Sulawesi.

Unlike washed, natural or honey processing, wet-hulling removes the coffee’s protective parchment layer while the beans still contain a relatively high amount of moisture. This unusual approach gives many Indonesian coffees their distinctive appearance and can contribute to their characteristic flavour profile.

🌿 How does wet-hulling work?

The process begins much like other coffee processing methods.

Ripe coffee cherries are harvested and the outer skin and some of the fruit are removed. The coffee is then allowed to ferment or is mechanically processed to remove the remaining mucilage.

The important difference comes next.

Rather than drying the coffee all the way down to the moisture level normally required for storage, the coffee is partially dried to around 30–35% moisture.

At this stage, the coffee is still relatively soft.

The parchment surrounding the coffee bean is then mechanically removed — or wet-hulled — exposing the green coffee inside.

The exposed beans are then dried again, this time to a stable moisture level suitable for storage and export.

This is where Giling Basah differs significantly from most other processing methods.

 How does wet-hulling affect flavour?

Wet-hulling is closely associated with the flavour characteristics often found in Indonesian coffees.

These can include:

• 🌿 Earthy or herbal notes
• 🌲 Woody characteristics
• 🍫 Rich chocolate flavours
• 🌰 Spices and nuts
• ☕ Heavy body
• 🍯 Low to moderate acidity
• A long, lingering finish

However, it’s important not to assume that every Indonesian coffee tastes the same.

Variety, altitude, soil, climate, farming, fermentation, drying and roasting all influence the final cup.

Wet-hulling is simply one part of the story.

Why does wet-hulled coffee look different?

One of the easiest ways to recognise wet-hulled Indonesian coffee is its appearance.

The green beans can have a distinctive deep green or blue-green colour, and they may look slightly different from the pale green beans commonly associated with washed coffees.

The unusual processing method, combined with Indonesia’s growing conditions, contributes to the distinctive identity of many Sumatran coffees.

🇮🇩 Why is Giling Basah associated with Indonesia?

Wet-hulling developed partly as a practical response to Indonesia’s warm, humid and often rainy climate.

Drying coffee to a low moisture level can be challenging in these conditions. Wet-hulling allows producers to remove the parchment earlier in the process, before completing the final drying stage.

The method has become closely associated with Indonesian coffee production and is now an important part of the region’s coffee identity.

And we have some superb Indonesian coffees to try at Acorns Coffee;

- Award Winning Monsoon Malabar

- Bold and Intense Hot Lava Java

- Our Suprisingly smooth bold Sumatra Mandheling

Wet-Hulled vs Other Processing Methods

The key difference is when the parchment is removed.

Washed

Cherry → fruit removed → fermented & washed → dried → parchment removed

Natural

Whole cherry → dried → fruit & parchment removed

Honey

Skin removed → mucilage retained → dried → parchment removed

Wet-Hulled

Fruit removed → partially dried → parchment removed while still wet → final drying

That unusual middle step is what makes Giling Basah so distinctive.

🔥 Why does this matter to a roaster?

When green coffee arrives at our roastery, its processing method tells us something about how it may behave during roasting.

Wet-hulled coffees can behave differently from washed or naturally processed coffees, so understanding the coffee’s journey from farm to green bean helps us decide how best to roast it.

For us at Acorns, that’s one of the fascinating parts of roasting single origin coffee. We’re not simply roasting a bag of green beans — we’re working with the result of a particular variety, place, climate, farming method and processing tradition.

Understanding that story helps us bring out the character that is already there.

Key Facts

• Giling Basah means wet-hulling and is strongly associated with Indonesia.
• The coffee is partially dried before the parchment is removed.
• The parchment is removed while the coffee still has relatively high moisture.
• The beans are then dried again to a stable moisture level.
• Wet-hulled coffees are often associated with heavy body, lower acidity and earthy, spicy or chocolate characteristics.
• The process developed partly because of Indonesia’s humid climate.

Did You Know?

The name Giling Basah translates roughly as “wet grinding” or “wet hulling” in Indonesian. The process isn’t actually grinding the coffee for brewing — it refers to the mechanical removal of the parchment while the coffee is still wet.

Coffee fermentation is a natural process that takes place during some methods of coffee processing. It happens when naturally occurring microorganisms such as yeasts and bacteria break down sugars and other compounds in the coffee cherry or its mucilage.

Fermentation isn’t something that happens only with experimental coffees. It has been part of traditional coffee processing for generations, particularly in washed coffees, where fermentation helps remove the sticky layer of mucilage left on the coffee bean after the fruit is removed.

However, producers can now deliberately control fermentation to influence the flavour and character of the finished coffee.

 How does fermentation work?

After coffee cherries are harvested, microorganisms naturally present on the fruit begin to consume sugars.

Depending on the processing method, fermentation can happen:

• In tanks containing coffee and water
• In sealed containers
• With the whole coffee cherry
• With the coffee bean and its remaining mucilage

As microorganisms consume sugars, they produce compounds such as acids, alcohols and other flavour compounds.

The producer can influence the process by controlling factors such as:

• Time
• Temperature
• Oxygen
• Moisture
• The microorganisms involved

Once fermentation has reached the desired point, the coffee is moved on to the next stage of processing, usually washing or drying.

⸻

How does fermentation affect coffee flavour?

Fermentation can have a significant influence on the final cup.

When carefully controlled, it can contribute to coffees with flavours described as:

• 🍓 Fruity
• 🍊 Citrusy
• 🍷 Wine-like
• 🍯 Sweet
• 🌸 Floral
• 🥭 Tropical
  

However, fermentation doesn’t simply mean “more fruity”.

Want to learn more about fruity coffee, though? Check out our guide - HERE.

Love fruity coffee, a lot? Then check out our Fruity Collection of coffees.

The flavour depends on the coffee itself, the microorganisms involved and exactly how the fermentation was managed.

Poorly controlled fermentation can produce unwanted flavours, which is why experience and careful monitoring are so important.

⸻

Fermentation isn’t the same as “fermented coffee”

This is an important distinction.

All coffee experiences some level of microbial activity during processing, but that doesn’t mean every coffee is marketed as a “fermented coffee”.

Traditional washed processing, for example, commonly uses fermentation to remove mucilage.

More experimental processing methods deliberately extend or control fermentation to create particular flavour characteristics.

This is where you’ll start seeing terms such as anaerobic fermentation, yeast fermentation and carbonic maceration appearing on specialty coffee bags.

⸻

Why are producers experimenting with fermentation?

Coffee producers are constantly looking for ways to improve quality and create distinctive coffees.

By controlling fermentation more carefully, producers can experiment with:

• Different fermentation times
• Different temperatures
• Oxygen levels
• Specific yeast or bacterial cultures
• Different coffee varieties

The aim isn’t simply to make coffee taste unusual. Done well, controlled fermentation can help enhance the natural characteristics of the coffee and create a more complex and memorable cup.

This is one of the reasons modern specialty coffee can be so exciting: producers are combining traditional knowledge with new approaches to processing.

⸻

What does “anaerobic” mean?

Anaerobic simply means “without oxygen.”

In anaerobic coffee processing, coffee is fermented in an environment where oxygen is restricted or excluded.

We’ll explore exactly how this works in the next question.

⸻

Key Facts

• Fermentation is a natural process involving microorganisms.
• Yeasts and bacteria consume sugars and produce other compounds.
• Fermentation can happen during traditional and experimental processing.
• Time, temperature and oxygen can all influence fermentation.
• Controlled fermentation can contribute to complex flavours.
• Poorly controlled fermentation can damage coffee quality.

Did You Know?

Fermentation isn’t unique to coffee. It’s also fundamental to the production of bread, cheese, yoghurt, beer and wine. In each case, microorganisms transform sugars and other compounds, creating new flavours, aromas and textures.

Anaerobic coffee processing is a method of processing coffee where the beans, usually still surrounded by some of the coffee cherry or its mucilage, are fermented in an environment with little or no oxygen.

The word anaerobic simply means “without oxygen.”

It has become increasingly popular in specialty coffee because carefully controlled anaerobic fermentation can create distinctive and sometimes surprisingly complex flavours.

How does anaerobic coffee processing work?

After the coffee cherries have been harvested and sorted, they are placed into a sealed or closed fermentation vessel.

The vessel might be a tank, barrel or specially designed container. By limiting the amount of oxygen available, the producer creates a very different environment from traditional open-air fermentation.

Naturally occurring yeasts and bacteria begin to consume sugars from the coffee fruit and mucilage. As they do, they produce different compounds that can influence the flavour and aroma of the coffee.

The producer carefully monitors the fermentation, controlling factors such as:

• Time
• Temperature
• Pressure
• Oxygen levels
• pH
• The condition of the coffee

Once the desired fermentation has been reached, the coffee is removed and continues through its particular processing method, which may involve washing, drying or another stage.

What does anaerobic coffee taste like?

This is where things get interesting.

Anaerobic processing can produce coffees with particularly intense and distinctive flavours.

You might find descriptions such as:

• 🍓 Red berries
• 🍍 Tropical fruit
• 🍷 Wine-like flavours
• 🍬 Candy-like sweetness
• 🌺 Floral aromas
• 🍊 Citrus
• 🥭 Fermented or exotic fruit

Some anaerobic coffees can have flavours that are dramatically different from what you might expect from the same coffee processed using a traditional method.

But there’s an important point:

Anaerobic doesn’t mean fruity.

The final flavour depends on the coffee variety, growing conditions, fermentation process, drying method and roasting. Anaerobic processing is simply one tool producers can use to influence the coffee’s character.

Is anaerobic coffee artificially flavoured?

No.

A well-produced anaerobic coffee hasn’t had fruit flavouring, wine or other ingredients added to it.

The flavours develop through the interaction between the coffee, microorganisms and controlled fermentation environment.

When you taste strong strawberry, tropical fruit or wine-like characteristics in an anaerobic coffee, those flavours have developed naturally during the coffee’s processing.

Why do producers use anaerobic processing?

Anaerobic fermentation gives producers another level of control over the processing of coffee.

Instead of allowing fermentation to happen largely in an open environment, producers can create specific conditions and monitor how the coffee develops.

This can help them:

• Develop particular flavour characteristics
• Increase sweetness
• Create greater complexity
• Highlight characteristics of a particular variety
• Produce distinctive coffees that stand out from more traditional processing methods

It requires considerable care, however. More fermentation isn’t necessarily better. If the process isn’t carefully controlled, undesirable flavours can develop and the quality of the coffee can suffer.

Anaerobic vs Traditional Fermentation

The simplest way to understand the difference is the environment in which fermentation takes place.

Traditional fermentation

☕ Coffee + mucilage

→ 🫧 Open environment

→ Microbial fermentation

→ Washing / drying

Anaerobic fermentation

☕ Coffee + mucilage

→ 🫙 Sealed environment

→ Limited oxygen

→ Controlled fermentation

→ Washing / drying

Both rely on microorganisms. The major difference is how the fermentation environment is controlled.

From Farm to Roastery

For us at Acorns, processing information is incredibly useful when we’re deciding how to approach a coffee in the roaster.

A coffee that has undergone controlled anaerobic fermentation may have very different characteristics from a washed coffee from the same country.

As roasters, we want to understand what the producer has created before we apply heat to the green coffee. The goal isn’t to roast those characteristics away, but to develop the coffee while allowing its unique character to shine through.

That’s what makes the journey from coffee cherry to roasted bean so fascinating.

Key Facts

• Anaerobic means without oxygen.
• Coffee is fermented in a sealed or controlled environment.
• Naturally occurring microorganisms break down sugars in the coffee.
• Time, temperature, oxygen and pH can all influence the fermentation.
• Anaerobic coffees can have intense fruity, floral or wine-like characteristics.
• Anaerobic coffee is not artificially flavoured.
• Careful control is essential to producing a high-quality result.

Did You Know?

Anaerobic fermentation isn’t actually unique to coffee. The same basic principle of controlling oxygen during fermentation is used in other foods and drinks, including wine and some fermented foods. Coffee producers have adapted these principles to create new ways of developing flavour in the coffee cherry.

Carbonic maceration is an experimental coffee processing technique inspired by methods traditionally used in winemaking. It involves fermenting coffee cherries in a carbon dioxide-rich environment, allowing the coffee to develop distinctive flavours and aromas during processing.

It has become increasingly popular within specialty coffee, particularly among producers looking to experiment with fermentation and create coffees with unusual levels of complexity.

 How does carbonic maceration work?

After ripe coffee cherries are carefully harvested and sorted, the whole cherries are placed into a sealed fermentation vessel.

Carbon dioxide is introduced into the vessel, displacing oxygen and creating an environment where the cherries ferment in the presence of CO₂.

The cherries remain sealed for a carefully controlled period. During this time, naturally occurring microorganisms inside and on the fruit contribute to the fermentation process.

Producers monitor factors such as:

• Temperature
• Time
• pH
• Pressure
• The condition of the cherries

Once the desired fermentation has been achieved, the cherries are removed from the vessel and dried, often using raised beds or patios.

The coffee is eventually hulled to remove the dried fruit and parchment, leaving the green coffee ready for export and, eventually, roasting.

Is carbonic maceration the same as anaerobic processing?

No — although they are closely related.

Both methods involve controlling the environment in which coffee ferments and restricting oxygen.

The key difference is that carbonic maceration specifically uses a carbon dioxide-rich environment, whereas anaerobic fermentation is a broader term describing fermentation carried out with little or no oxygen.

Think of it this way:

Anaerobic fermentation

🫙 A controlled environment with little or no oxygen

Carbonic maceration

🫙 A controlled environment where carbon dioxide is deliberately used

Carbonic maceration is therefore one particular approach to controlled, oxygen-restricted fermentation.

What does carbonic maceration coffee taste like?

Carbonic maceration can produce some remarkably distinctive coffees.

Depending on the coffee and the producer’s process, you might encounter flavours such as:

• 🍓 Strawberry and red berries
• 🍇 Grape
• 🍷 Wine-like characteristics
• 🍑 Stone fruit
• 🍬 Very pronounced sweetness
• 🌺 Floral aromas
• 🥭 Tropical fruit

Some coffees processed this way can taste almost wine-like or fruit-juice-like, with an intensity that is very different from more traditionally processed coffees.

But there is no single carbonic maceration flavour.

The coffee variety, growing conditions, fermentation time, temperature, drying and roasting all influence the final result.

Why would a producer use carbonic maceration?

For producers, carbonic maceration provides another way of experimenting with the flavour potential of coffee.

Rather than simply accepting the characteristics produced by a traditional processing method, producers can carefully manipulate the fermentation environment.

This can allow them to:

• Develop new flavour profiles
• Increase perceived sweetness
• Enhance fruit characteristics
• Create greater complexity
• Showcase unusual coffee varieties

It’s particularly interesting within specialty coffee because it gives producers another tool for expressing the character of a particular coffee.

Is more fermentation always better?

Definitely not.

Controlled fermentation requires considerable knowledge and precision. If the process is poorly managed, undesirable flavours can develop and the coffee can be damaged.

This is an important point when talking about experimental processing.

The aim isn’t to make coffee taste as “fermented” as possible.

The best producers use fermentation as a tool to enhance the coffee, rather than overwhelm its natural characteristics.

🔥 What does this mean for the roaster?

When a carbonic maceration coffee arrives at a roastery, the processing method becomes an important part of understanding the green bean.

The coffee may have developed intense fruit and fermentation characteristics before it has even been roasted.

Our job as roasters is then to develop those characteristics without allowing the roast itself to overpower them.

It’s another example of why we believe that great coffee starts long before it reaches the roaster.

The farmer and producer have already done an enormous amount of work. We get to continue the journey.

Key Facts

• Carbonic maceration is an experimental coffee processing technique.
• It is inspired by techniques used in winemaking.
• Whole coffee cherries are fermented in a controlled, CO₂-rich environment.
• Oxygen is restricted during the process.
• It can produce intensely fruity, sweet and wine-like characteristics.
• It is related to anaerobic fermentation but isn’t simply another name for it.
• Careful control of fermentation is essential.

Did You Know?

Carbonic maceration is particularly interesting because the technique has its roots in winemaking, where it is famously associated with the production of certain styles of wine. Coffee producers have adapted the principle to explore what happens when similar fermentation conditions are applied to coffee cherries.

How is Coffee Dried?

Once coffee has been harvested and processed, the coffee seeds — still known as green coffee — need to be dried. This is a crucial stage because the coffee must be dried carefully enough to become stable for storage and transport, without damaging the flavour potential created during processing.

The basic aim is to reduce the moisture content of the coffee to a safe level, usually around 10–12%, while drying it evenly and slowly.

How is coffee dried?

There are several methods used around the world:

Sun drying

Coffee is spread out on patios, raised African drying beds or other surfaces and left to dry naturally in the sun. Workers regularly turn the coffee to encourage even drying and prevent mould or unwanted fermentation.

This method is particularly important for natural processed coffees, where the whole coffee cherry is dried around the seed.

Mechanical drying

Some producers use mechanical dryers, particularly when weather conditions make natural drying difficult or when greater control is needed. Warm air is passed through the coffee to gradually remove moisture.

A combination of both

Many producers use a combination of sun drying and mechanical drying. Coffee might begin drying naturally and then be finished mechanically, helping the producer manage both quality and consistency.

Why does drying matter?

Drying isn’t simply about getting the coffee ready for storage. How quickly and evenly coffee dries can influence the final cup.

Drying too quickly can affect the development and stability of the coffee, while drying too slowly — particularly in humid conditions — can increase the risk of mould, unwanted fermentation or other defects.

Good drying requires patience, regular monitoring and plenty of attention from the producer.

What happens after drying?

Once the coffee has reached the appropriate moisture level, it can be stored as green coffee. Depending on the processing method, the coffee may still have parchment or other layers surrounding the seed, which are removed during later milling.

The finished green coffee can then be graded, sorted, packed and eventually shipped to roasters around the world.

And this is where our journey takes a big step closer to home — from green coffee to roasted coffee.

☕ Key Facts

• Coffee is normally dried to around 10–12% moisture.
• Sun drying is still widely used around the world.
• Raised drying beds allow air to circulate around the coffee.
• Mechanical dryers can provide greater control when weather conditions are difficult.
• Even, controlled drying helps protect the quality developed during processing.
• Once dried and prepared, coffee is known as green coffee — ready for the next stage of its journey.

Green coffee doesn’t look, smell or taste much like the coffee we know and love. The transformation happens when we roast it.

Roasting applies heat to green coffee, triggering a series of chemical and physical changes that develop the aromas, flavours, sweetness and body we associate with a good cup of coffee.

For a coffee roaster, this is where the real craft begins.

🔥 What does roasting actually do?

Green coffee contains carbohydrates, acids, proteins, water and many other compounds. When heat is applied, these compounds begin to react and change.

One of the most important reactions is the Maillard reaction. This occurs when amino acids and sugars react under heat, helping create many of the complex aromas and flavours found in roasted coffee.

As the roast progresses, the beans also become darker, lose moisture, expand and become more brittle.

Eventually, the pressure and gases building inside the beans cause them to crack — something roasters call first crack.

But roasting isn’t simply about making coffee darker.

Roasting develops flavour

The same green coffee can taste remarkably different depending on how it is roasted.

A lighter roast may preserve more of the coffee’s natural acidity and delicate characteristics, allowing things such as fruit, floral or citrus flavours to stand out.

A medium roast can develop more sweetness, caramelisation and chocolate or nutty characteristics.

A darker roast takes the coffee further, creating deeper roasted flavours and a heavier character, although too much heat or too long a roast can eventually overwhelm the coffee’s natural qualities.

The skill is finding the right balance.

At Acorns, we roast our coffees individually rather than treating every bean in exactly the same way. Different origins, varieties, processing methods and densities respond differently to heat.

 From green bean to coffee bean

When you watch green coffee being roasted, the transformation is surprisingly dramatic.

The beans begin cool and green. As they heat, they turn yellow, then progressively darker shades of brown. They release moisture and gases, expand and develop the aromas we instantly recognise as freshly roasted coffee.

By the end of the roast, something that barely resembles coffee has become the beans ready to be rested, ground and brewed.

And importantly, the roast doesn’t create everything from nothing.

The farm, variety, altitude, climate and processing method have already given the coffee its potential. Roasting is about unlocking and developing that potential.

The roaster’s job

This is why coffee roasting is both a science and a craft.

A roaster needs to understand the green coffee and control variables such as temperature, heat application, airflow and time throughout the roast.

At Acorns, we roast in small batches here in Hampshire, adjusting our approach to suit each coffee. The goal isn’t simply to produce a particular shade of brown — it’s to bring out what makes that particular coffee interesting.

Next time you drink an Acorns coffee, you’re tasting the result of a journey that began with a coffee cherry, travelled through farming and processing, and was finally transformed by heat in the roaster.

Key Facts

• Green coffee must be roasted to develop the familiar flavours and aromas of coffee.
• Heat causes complex chemical reactions, including the Maillard reaction.
• Roasting changes the bean’s colour, structure, moisture content and flavour.
• Lighter and darker roasts can emphasise different characteristics.
• Roast development should complement the qualities already present in the green coffee.
• First crack is a major milestone during the roasting process.
• Coffee roasting combines science, experience and careful control.

What Happens During Coffee Roasting?

Coffee roasting is a carefully controlled transformation. A green coffee bean goes into the roaster hard, pale and full of moisture — and comes out brown, aromatic and ready to become the coffee we know.

But what actually happens inside the roaster?

🔥 1. The coffee is heated

Green coffee is introduced into a hot roasting chamber, where heat begins moving into the beans.

At first, much of the energy is used to warm the beans and drive off their natural moisture. The beans gradually change from green to yellow, then develop increasingly brown shades.

The roaster carefully controls the temperature, heat application and airflow throughout this stage.

🌾 2. The beans turn yellow

As the coffee heats further, the beans begin to lose moisture and their colour changes from green towards yellow and light brown.

You may also notice aromas developing that are quite different from the finished coffee — sometimes reminiscent of grass, hay or toasted grain.

The beans are still a long way from being ready.

🍞 3. Browning and the Maillard reaction

As temperatures rise, a huge number of chemical reactions begin taking place.

One particularly important stage is the Maillard reaction, where amino acids and sugars react under heat to create hundreds of new flavour and aroma compounds.

This is one of the reasons roasting produces such a dramatic transformation.

The coffee becomes progressively browner and starts developing characteristics we associate with roasted foods — including caramelised, toasted, nutty and biscuit-like aromas.

💨 4. The beans expand

Water inside the beans turns to steam while gases are produced during roasting. Pressure builds inside the cellular structure of the coffee.

As this happens, the beans expand and become less dense.

Eventually, the pressure becomes strong enough for the beans to make a distinctive cracking sound.

This is known as first crack.

💥 5. First crack

First crack is one of the most important milestones for a coffee roaster.

The beans rapidly release steam and gases, producing a series of pops and cracks — a little like popcorn.

By this point, the coffee has undergone a huge transformation, but the roast isn’t necessarily finished.

How long the coffee continues roasting after first crack can have a significant effect on the final flavour.

This stage is particularly important when developing lighter and medium roasts, where the roaster is trying to balance sweetness, acidity, body and the coffee’s natural characteristics.

🎯 6. Development

The period after first crack is often called development time.

This is where the roaster decides how far to take the coffee.

Too little development can leave a coffee tasting underdeveloped, sharp or grassy. Too much can push the coffee towards heavier roasted flavours and potentially mask the characteristics that made the green coffee interesting in the first place.

There isn’t one perfect development time for every coffee.

Different beans respond differently to heat, which is why roast profiles are tailored to the coffee rather than simply following one recipe.

❄️ 7. The roast is stopped

Once the roaster reaches the desired point, the beans are rapidly cooled.

This is important because the beans remain extremely hot and would continue roasting if they were left to cool naturally.

At Acorns, we roast in small batches and monitor the roast closely, making adjustments according to the coffee we’re working with.

The result is a freshly roasted coffee ready for its next stage — resting and degassing before brewing.

☕ From green to roasted

The entire process can take only a matter of minutes, but during that time the coffee has changed dramatically.

Its moisture has been reduced, its structure has expanded, hundreds of new chemical compounds have formed, and its flavour potential has been developed through heat.

And this is why roasting isn’t simply about making coffee beans brown.

The roaster is deciding how to bring out the character of the green coffee.

☕ Key Facts

• Green coffee contains significant moisture and is much denser than roasted coffee.
• Heat drives off moisture and triggers complex chemical reactions.
• The Maillard reaction contributes to the development of roasted aromas and flavours.
• Coffee beans expand as pressure builds inside them.
• First crack occurs when steam and gases rapidly escape from the beans.
• Development after first crack influences the final balance and character of the coffee.
• Beans are rapidly cooled at the end of the roast to stop further roasting.
• Different coffees require different roast approaches.

Continue Your Coffee Journey →

What is First Crack?

What is First Crack?

If you’ve ever stood beside a coffee roaster while it’s running, you’ll eventually hear it: a series of sharp pops and cracks coming from the beans.

This is first crack — one of the most important moments in the coffee roasting process.

💥 What actually causes first crack?

As green coffee is heated, moisture inside the bean turns into steam. At the same time, chemical reactions during roasting produce gases and the bean’s internal structure begins to expand.

Pressure gradually builds inside the coffee bean.

Eventually, that pressure becomes strong enough to fracture the bean’s structure, causing it to expand and release steam and gases.

The result is the distinctive cracking sound we call first crack.

It can sound a little like popcorn popping, although the sound varies considerably between coffees.

👂 What does first crack tell a roaster?

First crack gives the roaster an important indication of how far the coffee has progressed.

By this stage, the coffee has already changed dramatically from its original green state. It has lost much of its moisture, expanded significantly and developed many of the compounds responsible for its roasted aroma and flavour.

But first crack doesn’t mean the roast is finished.

For many coffees, particularly lighter and medium roasts, the period after first crack is where the roaster carefully develops the flavours they want.

🎯 Development after first crack

The time between the beginning of first crack and the end of the roast is often referred to as development time.

This is a delicate part of the roast.

Too little development can leave a coffee tasting underdeveloped, sharp or vegetal. Too much can push it towards heavier, roast-driven flavours and reduce some of the characteristics that came from the coffee’s origin and processing.

The right balance depends on the individual coffee.

A dense Ethiopian coffee, for example, may behave very differently in the roaster from a lower-density Brazilian coffee. The roaster therefore needs to watch and listen rather than simply follow a fixed temperature or timer.

🌡️ Is first crack always at the same temperature?

Not exactly.

First crack often occurs somewhere around 195–205°C, but there isn’t a single temperature that applies to every coffee or every roaster.

Bean density, moisture, processing method, batch size, roasting equipment and the way heat is applied can all influence when first crack occurs.

This is why experienced roasters pay attention to more than the number on the temperature display.

Sight, smell, sound and the behaviour of the beans all matter.

☕ Why does first crack matter to your coffee?

First crack is one of the points where the roaster can make important decisions about the direction of the roast.

Stop the roast soon after first crack and the coffee may retain more of its delicate, origin-driven characteristics. Continue further and more developed caramelised and roasted flavours can become prominent.

Neither approach is automatically better — the aim is to find the point that suits the particular coffee and the flavour profile the roaster is trying to achieve.

At Acorns, first crack is one of the moments we listen for and monitor closely during every roast.

☕ Key Facts

• First crack is caused by pressure building inside the coffee bean during roasting.
• Steam and gases escape as the bean’s structure fractures and expands.
• It sounds like a series of pops or cracks.
• First crack is an important milestone, but it isn’t the end of the roast.
• The period afterwards is commonly called development time.
• First crack doesn’t occur at exactly the same temperature for every coffee.
• Roasters use sound alongside temperature, aroma, colour and bean behaviour to judge the roast.

What is a Light, Medium and Dark Roast?

You’ll often see coffee described as light roast, medium roast or dark roast. These terms broadly describe how far the coffee has been roasted, rather than the type or origin of the coffee.

The important thing to remember is that roast level isn’t a measure of quality. It is a choice made by the roaster about how the coffee’s characteristics should be developed.

🌱 Light roast

A light roast is taken to a relatively early point in the roasting process, usually shortly after first crack.

Because less of the coffee’s character has been changed by prolonged roasting, light roasts can allow more of the characteristics associated with the origin, variety and processing method to come through.

You might find flavours described as:

• Fruity
• Floral
• Citrus
• Berry-like
• Bright or lively
• Sweet and delicate

Lightly roasted coffees can also have more noticeable acidity. In coffee, acidity isn’t necessarily a bad thing — it can provide the fresh, lively quality that makes some coffees particularly interesting.

Our Ethiopia Yirgacheffe, for example, can show the bright, floral and fruity characteristics that make Ethiopian coffees so distinctive.

☕ Medium roast

Medium roasting takes the coffee further, allowing more sweetness, body and developed flavours to emerge while still retaining much of the coffee’s origin character.

Medium roasts commonly show characteristics such as:

• Chocolate
• Caramel
• Nuts
• Toffee
• Dried fruit
• Balanced sweetness
  

This is a particularly versatile style of roast and works well across a range of brewing methods.

Our Colombia Finca Sofia is a good example of a coffee where roasting is used to develop its smooth, sweet and chocolatey characteristics.

🔥 Dark roast

A dark roast is taken further into the roasting process, producing a darker brown bean and more pronounced roasted flavours.

You may find characteristics such as:

• Dark chocolate
• Toast
• Smoke
• Spice
• Roasted nuts
• A heavier body
  

As roasting progresses, the flavours created by the roasting process become increasingly dominant. Eventually, they can mask many of the characteristics that came from the original green coffee.

That’s why dark roasting needs care. Dark doesn’t automatically mean stronger, better or more caffeinated.

And we can dark roast your beans, to order, coffee’s such as Kenya Samburu, surprising work really well darker roasted.

🎯 What does roast level actually change?

Roast level can influence the balance between the coffee’s natural characteristics and flavours developed during roasting.

A lighter roast may allow more origin-driven acidity and fruit characteristics to shine. A medium roast can bring sweetness and balance to the forefront, while a darker roast can emphasise deeper, roasted flavours.

But these are general tendencies, not rules.

Two coffees roasted to a similar level can taste completely different because the green coffees themselves are different.

💡 What about “strong” coffee?

This is where things can get confusing.

When someone says they want a strong coffee, they might mean a coffee with:

• More caffeine
• A stronger flavour
• More body
• A darker roast
• A higher coffee-to-water ratio
  

These are all different things.

A dark roast isn’t automatically more caffeinated, and a lighter roast isn’t automatically weak.

At Acorns, we often talk about flavour strength rather than simply roast darkness. A coffee can have a bold, intense flavour without needing to be roasted extremely dark.

Read more about our thought’s on Strong coffee in our guide.

☕ Key Facts

• Light, medium and dark describe how far a coffee has been roasted.
• Light roasts can highlight fruit, floral flavours and acidity.
• Medium roasts often balance origin characteristics with sweetness and body.
• Dark roasts emphasise more developed, roasted flavours.
• Roast level doesn’t determine coffee quality.
• Dark roast does not automatically mean more caffeine.
• “Strong” can mean different things — flavour, body, concentration or caffeine.
• The best roast level depends on the coffee and the flavour the roaster is trying to develop.

Does Dark Roast Coffee Have More Caffeine?

This is one of the most common questions about coffee — and the answer is not as simple as light or dark roast.

A darker roast doesn’t automatically contain more caffeine. In fact, roasting has a relatively small effect on the caffeine content of the coffee bean compared with other factors such as the type of coffee, dose and brewing method.

☕ What happens to caffeine during roasting?

Caffeine is relatively stable at normal coffee-roasting temperatures, so most of the caffeine present in the green coffee remains in the roasted bean.

What does change is the physical structure of the bean.

As coffee roasts, it loses moisture and becomes less dense. It also expands, meaning that a scoop of dark roasted coffee contains fewer beans by weight than the same volume of a lighter roast.

This is why statements such as “dark roast has more caffeine” or “light roast has more caffeine” can both be misleading.

⚖️ Weight or volume matters

If you measure your coffee by weight, the caffeine difference between light and dark roast is generally relatively small.

If you measure coffee by volume, however, the difference can become more noticeable because roasted beans change in size and density as the roast progresses.

A scoop of coffee isn’t necessarily the same amount of coffee by weight.

That’s one reason we recommend measuring coffee by weight rather than relying on scoops when you want a consistent brew.

🌱 Arabica vs Robusta

The type of coffee bean can make a much bigger difference.

Robusta (Coffea canephora) generally contains considerably more caffeine than Arabica (Coffea arabica).

Our Vietnam Son La is a Robusta coffee, while many of our other single origins are Arabica. So if you’re looking for a naturally higher-caffeine coffee, the species can be a much more important factor than whether the coffee is light, medium or dark roasted.

What about “strong” coffee?

This is where caffeine and flavour often get confused.

A coffee can taste bold, intense or bitter without containing significantly more caffeine.

Equally, a lighter roast can taste bright and fruity while still delivering plenty of caffeine.

If you want more caffeine in your cup, factors such as how much coffee you use, the coffee species and your brewing method are more useful things to consider than simply choosing a darker roast.

☕ Key Facts

• Dark roast coffee does not automatically contain more caffeine.
• Most of the caffeine in coffee survives the roasting process.
• Coffee beans lose moisture and become less dense as they roast.
• Measuring coffee by weight gives you more consistency than measuring by volume.
• Robusta generally contains more caffeine than Arabica.
• Flavour strength and caffeine strength are not the same thing.
• Your coffee dose and brewing method can have a significant effect on the caffeine in your cup.