The phases of coffee roasting

Coffee roasting happens in several distinct phases, each marked by chemical and physical changes in the beans that shape the flavor, aroma, and color of the final coffee. 

We have two main things to control: Time & Temperature.

We also need to monitor the rates of rise (steepness of the time/temp curve) during roasting .

Each phase will have a target time, temperature and rate of rise (ROR).

It's important to note events like when the colours of the beans change,

when they start to change their smell (things like bread or sweetness) or when we reach first crack, etc.

It's helpful if you write down the temperatures (every 30 secs).

While terminology can vary slightly among roasters, here are the main phases commonly recognized:

Notice that the ROR tends to descend as we progress through the different phases.

That is the ROR gradient for the browning phase is gentler than the drying phase.

☕ 1. Drying Phase (Endothermic)

Temperature range: ~100°C–160°C (212°F–320°F)

Duration: 4–8 minutes (depending on roast profile)

Green coffee starts with about 10–12% moisture.

Heat is applied to evaporate this water without burning the beans.

Beans turn from green to a light yellow and begin to smell grassy or hay-like.

The roasting environment absorbs energy (endothermic process).

Goal: Properly remove moisture to prepare beans for chemical reactions in later stages.

Don't rush this phase or the inside of the bean may not get evenly dried 

🌾 2. Maillard Reaction Phase (Browning Phase)

Temperature range: ~160°C–190°C (320°F–375°F)

Sugars and amino acids react (the Maillard reaction), creating brown pigments and complex flavor precursors. 

The bean color deepens from yellow to light brown.

Caramelization and sweetness actually start to develop  when beans turn yellow.

Caramelization = applying heat to the natural sugars inside the coffee beans to bring out sweetness.

Amino acids are what give acidity when they are heated.

Aromas shift from grassy to toasty, nutty, and bread-like.

Internal bean pressure starts building as gases (CO₂, water vapor) form.

Goal: Develop the foundational flavors and aromas that define the coffee’s character.

Timing this phase is very important ... its must not be too fast or too slow.

Too Fast:

It is important not to rush this phase or the coffee can turn out too bitter or tart.

Or if this phase is rushed, the caramelization or acidity may not form.

Too Slow:

The chemical reactions become muted and we loose acidity ... we end with a bitter/flat/baked coffee

🌋 3. First Crack (Exothermic)

Temperature range: ~196°C–205°C (385°F–400°F)

Internal pressure causes the beans to crack open audibly.

This marks the transition from endothermic to exothermic — the beans release energy.

The coffee expands in size, and oils may begin to migrate toward the surface.

Goal: Achieve the first clear milestone of roast development — suitable for light roasts.

🌑 4. Development Phase (Roast Development Phase)

Temperature range: ~205°C–220°C (400°F–430°F)

After the first crack, the roast can be stopped or continued depending on desired profile.

Caramelization and pyrolysis intensify, creating sweetness, body, and deeper flavor.

Roasters control time here carefully to balance acidity, sweetness, and bitterness.

The longer you go into this stage, the less sweet and acidity you will get and the more bitter your coffee will be. 

The longer this stage , the more you are roasting out the sweetness & acidity.

Goal: Fine-tune the flavor — too short can taste sour/undeveloped; too long can taste bitter or smoky.

Here you can balance acidity (the fruit bomb) or sweetness

🔥 5. Second Crack (Optional – for Dark Roasts)

Temperature range: ~224°C–230°C (435°F–446°F)

Beans crack again (softer and quieter).

Cell structure breaks down, and oils appear on the surface.

Flavors become darker, more roasted, with smoky or even burnt notes if pushed too far.

Goal: Produce darker roasts such as French or Italian — bold, less acidic, more bitter.

⚙️ 6. Cooling Phase

Immediately after roasting

Beans are rapidly cooled (usually by air or water) to stop further roasting.

Proper cooling locks in the developed flavors and prevents over-roasting.

Would you like me to include a temperature/time curve diagram showing these phases visually? It’s a great way to see how roast development progresses.

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Peru coffee growing regions

Peru's main coffee-growing regions are its northern, central, and southern highlands, each producing unique flavor profiles due to varying altitudes and climates.

Notable areas include Amazonas, Cajamarca, and San Martín in the north; Junín (Chanchamayo) in the central region; and Cusco and Puno in the south. These regions produce a range of Arabica coffees, from mild and nutty to fruity and complex, with high-altitude beans often showing brighter acidity. 

Northern Highlands

Regions: Amazonas, Cajamarca, and San Martín.

Characteristics: Situated on the eastern slopes of the Andes, this region features a mix of jungle and mountain geography.

Flavor Profile: Cajamarca is known for its bright acidity and clean cup, while the Amazon region is noted for fruity and tropical notes and a fuller body. 

Central Highlands

Regions: Junín, particularly the Chanchamayo and Satipo provinces.

Characteristics: Located in the central Andes, coffee is grown at elevations typically ranging from 900 to 1,800 meters.

Flavor Profile: Often produces balanced, smooth coffees with mild acidity and nutty or chocolatey notes. High-altitude beans can be more fruity with intense acidity and a creamy body.

 

Southern Highlands

Regions: Cusco, Ayacucho, and Puno.

Characteristics: This area is known for its specialty coffee production, benefiting from rich soils and unique microclimates.

Flavor Profile: Coffees from this region can have bold, earthy flavors and nutty tastes, often with mild acidity due to the higher altitudes. 

Sumatra (Indonesia)

 Coffee from Sumatra (an island in western Indonesia) is famous in the specialty coffee world for its distinctive flavor profile, unique processing methods, and rich history. 

Here are the key points:

🌱 Origin & Varieties

Grown primarily in the highlands of Aceh (Gayo), Lintong, Mandheling, and Sidikalang.

Most farms are smallholder plots (often less than a hectare per farmer).

Common varieties: Typica, Catimor, and hybrids adapted to local conditions.

☕ Flavor Profile

Sumatran coffees are often described as:

Full-bodied & syrupy – heavier mouthfeel than most other origins.

Low acidity – smooth, mellow, sometimes earthy.

Flavor notes – chocolate, tobacco, cedar, spices, herbs, sometimes tropical fruit.

Often a little "earthy" or "funky", which many coffee lovers prize.

🌀 Processing Method: Giling Basah (Wet Hulling)

A hallmark of Sumatran coffee.

After fermentation, beans are parchment-dried only to ~30–40% moisture (instead of the usual 10–12%).

Farmers then wet-hull (remove the parchment layer while still moist) and continue drying.

This process gives Sumatran coffee its deep, complex, and sometimes rustic flavors, but also contributes to its unique bluish-green raw bean color.

🌍 Cultural & Economic Importance

Coffee has been grown in Sumatra since the Dutch colonial period (1600s–1700s).

It was introduced by the Dutch East India Company.

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🌍 Main Sumatran Coffee Regions (Side-by-Side)

Region / Name	Location	Flavor Profile	Notes
Mandheling	North Sumatra, near Lake Toba	Heavy body, low acidity, earthy, chocolate, herbal, sometimes tobacco	The most famous Sumatran coffee; "Mandheling" isn’t a place but an ethnic group — the name stuck in trade.
Lintong	Southwest of Lake Toba (Lintong Nihuta area)	Cleaner, brighter than Mandheling, with herbal, spicy, citrus, and floral tones	Considered a “refined” version of Sumatran coffee; often preferred in specialty circles.
Gayo (Aceh)	Aceh highlands, northern tip of Sumatra	Balanced, complex, sweet, syrupy body with cocoa, red fruit, and spice notes	Grown at higher altitudes (up to 1,700+ m), often organic; one of the most prized.
Sidikalang	West of Lake Toba, near Bukit Barisan mountains	Bold, full-bodied, chocolate, nutty, slight fruitiness	Less well-known but increasingly recognized for quality.

 

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Aceh

Elevations are between 900 - 1500m. The highlands are cool but humid.

The region is rich in volcanic soil.

These are optimal growing conditions for Arabica varieties such as: Ateng, Gayo 1, Timtim, and Abyssinia.

Links:

+ https://colipsecoffee.com/blogs/coffee/sumatra

+

+

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Coffee index. Click here :

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Indian Coffee growing regions

 India's coffee regions are primarily categorized into three areas: 

1. traditional regions in Karnataka, Kerala, and Tamil Nadu in the south; 

2. non-traditional regions like Andhra Pradesh and Odisha in the Eastern Ghats; 

3. the Northeastern states, including Assam, Manipur, Meghalaya, Mizoram, Tripura, Nagaland, and Arunachal Pradesh.

Karnataka, particularly the Bababudangiris where coffee was first introduced, is the largest coffee-producing state. 

Traditional Regions: Karnataka, Kerala, and Tamil Nadu 

Karnataka: The largest coffee-producing state, with regions like Coorg and Chikmagalur being historically significant. 

The Bababudangiri hills are known as the birthplace of coffee in India.

Kerala: A major coffee hub, particularly in the Wayanad district, which cultivates both Arabica and Robusta beans, with Robusta being more dominant.

Tamil Nadu: Coffee is grown in the Anaimalai hills and the Nilgiris, often in high-elevation plantations that produce Arabica with bright acidity. 

Non-Traditional Regions: Andhra Pradesh and Odisha 

Andhra Pradesh: The Araku Valley is a growing specialty coffee region recognized for its tribal cooperative-led production.

Odisha: The Koraput region is another area gaining recognition for growing Arabica coffee.

Northeastern Regions 

The "Seven Sister States": This region includes Assam, Manipur, Meghalaya, Mizoram, Tripura, Nagaland, and Arunachal Pradesh. 

These states are considered a rising frontier for coffee production, with areas like the Cachar district in Assam growing both Arabica and Robusta. 

Key characteristics of Indian coffee 

Growing conditions: Coffee is often shade-grown under a two-tier canopy, which can lead to a richer flavor. The variety of altitudes and rainfall patterns (ranging from 800mm to 4500 mm) contribute to diverse flavor profiles.

Monsooned coffee: A unique process where beans are exposed to humid monsoon air, resulting in a distinctively mild, low-acid, pale gold bean known as Indian Monsoon Malabar.

Bean varieties: Both Arabica and Robusta are grown, with notable varieties including Kent and S. 795.

Papua New Guinea (PNG)

Coffee from Papua New Guinea (PNG) is quite unique in the coffee world. 

🌱 Origin & Growing Conditions

• Coffee was first introduced to PNG in the late 1800s, but commercial production began in the 1930s.
• Most coffee comes from the Eastern Highlands and Western Highlands regions.
• The country’s volcanic soils, high altitudes (1,200–1,800m), and tropical climate make it ideal for high-quality Arabica beans.
• Farms are often smallholder plots, meaning families grow coffee in “coffee gardens” alongside bananas, papayas, and root crops.

☕ Flavor Profile

• PNG coffee is known for being bright, clean, and complex, similar in some ways to washed Ethiopian coffees, but with its own twist.

• Common tasting notes:

  • Fruity (citrus, stone fruit, tropical fruit)
  • Floral (jasmine, hibiscus)
  • Nutty or chocolaty undertones
  • Medium body with crisp acidity.

• Compared to Indonesian coffees (like Sumatra), PNG is usually cleaner and lighter, without as much of the earthy, spicy notes.

🔑 Types & Varieties

• Almost all is Arabica, especially Typica, Bourbon, and Arusha varieties.
• Robusta is just starting to be grown (in the costal lowlands)
• Most PNG coffee is washed/fully washed (wet processed), which highlights brightness and clarity.

🌍 Coffee Culture & Market

• Coffee is PNG’s second-largest agricultural export after palm oil.
• Because many farmers are smallholders, infrastructure challenges (roads, mills, logistics) can make quality control tricky.
• When well-processed, PNG coffees are highly prized by specialty roasters around the world.

👉 In short: Papua New Guinea coffee is bright, fruity, and floral—a hidden gem that sits between the clean fruitiness of East Africa and the heavier, earthier flavors of Indonesian coffees.

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Major Coffee Regions in Papua New Guinea

1. Western Highlands

• Key Estates: Sigri, Kimel, Korgua
• Altitude: 1,400–1,800m
• Profile: Clean, bright, citrusy with chocolate undertones.
• Notes: This is where some of PNG’s most famous estates are located. The Western Highlands is considered the “heart” of PNG specialty coffee.

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2. Eastern Highlands

• Key Town: Goroka (a hub for coffee trade and cupping)
• Altitude: 1,500–1,800m
• Profile: Fruity (stone fruits, tropical fruit), floral, medium body.
• Notes: Often described as more delicate and tea-like compared to Western Highlands coffees.

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3. Simbu (Chimbu) Province

• Altitude: 1,400–1,800m
• Profile: Winey acidity, herbal and nutty notes, sometimes spiced chocolate.
• Notes: Often produced by smallholder farmers, making quality more variable, but the best lots are very distinctive.

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4. Morobe Province

• Altitude: 1,200–1,600m
• Profile: Bright citrus (orange, grapefruit), with a lighter body.
• Notes: Less known internationally, but can produce crisp, vibrant coffees thanks to fertile soil and rainfall.

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5. Enga & Jiwaka Provinces

• Jiwaka: Split off from Western Highlands in 2012; produces coffee similar to that region, with citrusy brightness and smooth body.
• Enga: A newer coffee-producing area, still developing, but with potential for high-grown specialty lots.

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🌱 Famous Estates (Consistently High-Quality)

• Sigri Estate (Western Highlands): Legendary in the specialty world; produces washed Arabica with elegant acidity, balance, and tropical fruit notes.
• Kimel Estate (Western Highlands): Known for structured body, nutty sweetness, and clean finish.
• Korgua Estate (Western Highlands): Rich, complex cups with chocolate and fruit layers.

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👉 So, in summary:

• Western Highlands = classic, balanced, world-renowned (Sigri, Kimel, Korgua).
• Eastern Highlands = brighter, more floral and fruity.
• Simbu = complex, sometimes winey.
• Morobe = citrusy and clean.

Indonesia - general

Indonesia's main coffee-producing regions are the islands of Sumatra, Java, and Sulawesi, each with distinct characteristics. 

Sumatra is the largest producer, known for bold, earthy coffees like Mandheling and Ankola. 

Java is famous for Arabica with bright acidity, though it also produces Robusta.

Sulawesi is known for high-quality Toraja coffee, which has a unique, fragrant, and savory taste. 

Sumatra

The largest producer, contributing up to 75% of Indonesia's total coffee output. 

Key areas:

Lampung, South Sumatra, Bengkulu, and Aceh. 

Flavor profile:

Bold, earthy, and low-acidity coffee due to the semi-washed processing method. 

Notable varieties:

Sumatra Mandheling and Ankola are famous for their smoky, toasted, and complex flavors. 

Java

The first island where coffee was grown in Indonesia, with major production in East, West, and Central Java. 

Flavor profile:

Typically known for Arabica with bright acidity and fruity notes, though it also produces Robusta. 

Notable varieties:

Some Java coffee can be aged to achieve a deeper, earthier flavor profile, with notes of tobacco or leather. 

Sulawesi

An important growing region, with high-quality coffee from areas like Tana Toraja and Enrekang. 

Flavor profile:

Unique, often with a strong aroma and savory taste, possibly due to growing alongside spice plants. 

Notable varieties:

Toraja coffee is highly sought after for its distinctive character. 

Other regions

Bali:

Farmers grow coffee on the slopes of volcanoes, producing a smooth, non-bitter coffee with notes of citrus, walnuts, and chocolate. 

Flores:

Grown in the rich volcanic soil near Bajawa, producing high-quality Arabica. 

Kalimantan (Borneo):

Also produces coffee, but in smaller volumes

ELK Elektroniks - KOLOR Module - update

 Some updates for the new LED KOLOR module.

This is a eurorack module designed to control LED strips, squares, etc.

View this post on Instagram

A post shared by Music Tech, Synth, Keyboard Repairs (@elk_elektronik)

....

The module will be released as a kickstarter project.

More info can be found at Ed's official website

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Londinium profile

Londinium is a brand of coffee machine that hail from the UK.

They primarily focus on lever machines.

These machines have become famous for their unique style of shots

to the point that many baristas have tried to emulate the 

"Londinium shot" on other machines.

My moddified Gaggia Classic (Gagguino) and Rancilio Silvia (Gaggimate) have "Londinium Profiles".

The Decent also has something similar.

So what is it?

It's a spring lever machine that uses pressurised pre-infusion at the beginning..

The technique it uses is something like a GS3 puck slam.

It really slams the puck with something like 25mls of water.

This very fast and early saturation of the puck compresses it much faster than is usual leading to a denser & thicker starting pour.

It's sometimes called a "water hammer".

The adapted "Londinium profile" for a standard lever machine involves

quickly hitting the puck with pressure (called the puck slam .. it's about 3-4 bar) 

holding it there.

Notice the initial flow rate is about 9ml/s then drops to 0.3ml/s.

The "standard Spring lever profile" has a much lower pre-infusion pressure. (About 1bar)

+  Spring lever pressure profile.

3 Bar appears to be the perfect pressure to balance capillary preinfusion with pressure preinfusion.

(3 Bar is also common in "Blooming profiles").

This gets the water through the puck evenly & quickly  & hopefully this will result in minimal channeling.

The initial flow rate needs to be really low ... about 8ml/s (0.3 to 0.5g/s) range.

This will give you a beautiful thick top to your espresso.

After this, ramp up to 9 bar, then gradually drop back to zero

as the puck degrades.

Try to keep the flow rate constant during this second stage.

This second stage has much less body.

Sometimes, after the shot reaches 9 bar, the pressure declines more slowly (than in the above Gagguino example) ... or sometimes it even hangs around the 9-8 bar range.

It all depends on the flow rate.... the important idea is to keep the flow rate constant.

When you drink a shot like this it feels super creamy due to the thick top of the preinfusion.

This pic is the graph from my Rancilio Silvia (Gaggimate mod).

The Londinium preset settings for this machine were 18g in, 36g out.

I used a DF64v grinder at setting 12. (1000 rpm).

Temp 93c

Pre-infusion 3 bar (14 sec)

Ramp up to 9 bar (1 sec)

then drop to 8bar, 7bar, 6bar, 5bar.

Hold at 5 bar for the rest of the shot until you reach your desired final weight.

The duration of each step & the final shot length will depend on the grind size.

I think my grind size was a little to fine ...as it took 43sec to get 36g out.

I'll dial the DF64 to setting 10 next time.

So for this Gaggimate - Londinium profile I decided to maintain the final pressure at 5bar but this could be lower ... maybe 4 or 3 bar ?? 

Some profiles use higher pressures. 

I think it all depends on keeping a steady final flow rate and thus maintaining puck integrity.

In summary:

1. Pre-infuse:  8 ml/s, low pressure & hold at 3 bar.

                   (About 13 secs). At this point, the puck is held in a compressed state.

2. Post infusion: raise pressure and hold at 9 bar.

3. Final stage: decline to 5-3 bar (and hold at this pressure)

You need to monitor the flow in these last stages.

Your aim is to keep the flow at about 2g/sec (2ml/sec).

This profile works really well on dark to medium roasts.

Usually, I aim for a 1:2 ratio

One important think to note is that although I use the measurement of pressure a lot, what is also important is flow.

Pressure = flow x resistance

This type of shot is really tasty with milk based coffee like Latte

Below is a graph from Decent.

Temp is around 89C

The flow changes quite a bit.

... up to 8ml/sec (puck slam) then back to 2ml/s 

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Coffee index. Click here :

https://djjondent.blogspot.com/2024/03/coffee.html