First Crack, A Look Into the Roasting Process

The roasting process is a complex series of chemical reactions and changes.  A roaster’s job is to control these reactions to produce an excellent bag of coffee.  Let’s take a look at the roasting process.

Green Beans

We get coffee imported from all over the world.  Green coffee is packaged in burlap bags that weigh around 150 pounds.  The bags are shipped on a pallet, thus bringing us to the first step in our production process.  The beans are unloaded into barrels corresponding to their country of origin.  We roast all of our coffee to order, so our production begins when you place an order.  We compile all of the orders for the day and load the data into a spreadsheet.  This calculates how much coffee we need to roast to fulfill all the orders.  Once the roaster is on, we line up the barrels in the order they will be produced in.  We start by scooping the green beans into a smaller barrel to transport them to the roaster.  Each batch is carefully weighed to ensure we make a consistent product.  After the beans are loaded in the hopper, the roasting process truly begins.

The Roasting Process

Heating Up

roasting diagramAt Copper Canyon Coffee, we do our roasting on a Probat L-12.  The roaster is made of a cast iron drum that spins over a flame to heat up the coffee.  Since the drum is solid metal, it takes a little bit to heat up and cool down.  Our roaster runs on natural gas.  Every morning, the first step in production is to turn the roaster on.  After the roaster is on it takes 20-30 minutes to warm up.  This time depends on the ambient temperature, taking longer in the winter and shorter in the summer.  The roaster takes in air and gas, lighting a fire at the base of the drum.  The drum rotates and heats up, expelling hot air out through the exhaust.  The coffee is loaded into the hopper and released into the drum with the hopper lever.  Once the coffee is in the drum it goes through a series of chemical changes until it becomes the beans you know and love.

Roasting the Beans

roaster diagram frontEach roaster has a different capacity.  This roaster can take around 20 pounds of green beans in each batch.  A batch takes around 12 minutes.  The beans tumble around the drum inside, and change color over the course of the roast.  You can see this change in color through the sight glass.  This is a small window on the front of the roaster.  During the roast, it is important for the roast master to keep an eye on the beans.  While there is a guide for each roast, factors like precipitation and humidity can cause fluctuation in the product.  To account for these changes, the roast must be monitored closely.  Another way the roast master monitors the beans is with the sample spoon.  In this picture, Sean is holding the sample spook and smelling the beans to inspect their aromatics.  The spoon is normally stored in the hole down and to the left of the sight glass.  

Chemical Changes

roasting reactions

There are several different things that happen inside the roaster.  The main chemical reaction is known as the Maillard reaction.  This is the name for the caramelization of sugars within the bean.  It is a non-enzymatic reaction between amino acids and reducing sugars that causes coffee beans to “brown”.  The Malliard reaction is not specific to coffee, in fact it happens when food is cooked.  The process causes a darkening in color and a release of aromas.  It is the same process that causes your morning toast to brown.  In coffee, the reaction produces an abundance of flavor and aromatic compounds which contributes to its distinct taste.  This is heavily influenced by the region/ground that the bean is grown in.  Coffee is very much affected by minerals and the composition of the soil it was grown in.  

While the Maillard reaction is happening, there are a few notable checkpoints known as “cracks”.  As the roaster heats up the bean, the moisture inside is also heating up.  At the end of the roasting process the beans are usually over 400 degrees (Fahrenheit).  This is far greater than the 212 degrees needed to boil water.  The first crack is a checkpoint for when the water inside the bean starts to boil.  This causes the bean to crack and expand as the steam evaporates out of the bean.  

Water isn’t the only type of moisture to evaporate out of the bean.  Coffee beans are filled with oils that heat up and evaporate off during the process.  When these oils reach their boiling point they cause the beans to reach the second crack.  The shell of the bean cracks and the bean expands even more.  Right after the second crack the beans have usually doubled in size from the green beans loaded in the roaster.

It is important to note that not all coffee reaches the second crack.  Most light and medium roasts are pulled out at varying points between the first and second crack.  At Copper Canyon Coffee, we tend to have a lighter roasting profile meaning that only our very darkest roasts reach the second crack.  After the second crack it is very easy for the coffee to get a burnt taste so it must be very closely monitored.  

Dumping the Roast

When the roast hits its final temperature, it needs to be dumped.  Using the bean release lever, the roast master dumps the beans into the cooling tray.  The center of the tray spins the various rakes around the tray.  This helps turn the beans over so they can all be cooled evenly.  The beans typically stay in the cooling tray for 8-10 minutes while the next batch is roasting.  When the beans are no longer radiating heat, they are ready to be dumped out of the cooling tray.  Using the lever on the discharge port, the roast master can dump the beans into a bucket.  At this point the beans are ready to be put in the packaging lineup.

Cool Down

Once all of the roasting has been completed, the roaster needs to be cooled down.  At the end of the roast, the temperature is over 400 degrees.  Even if you are not actively roasting, leaving the roaster unattended at this temperature can be dangerous.  The cool down process usually takes 30-45 minutes.  We first turn off the gas, but we leave the motor going.  Similar to the cooling tray, leaving the motor on allows airflow to the entire roasting drum.  The cast iron drum takes a while to cool down.  Once it has cooled down under 100 degrees, or just above the ambient temperature, we turn off the motor.  This completes our roasting process for the day.  After that, the coffee is ready to be packaged and shipped before it is enjoyed by customers all across the country.

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