Roast Coffee at Home




Introduction: Roast Coffee at Home

About: I'm a 49 year old Systems Architect living in the Midwestern United States. After travelling the world for 20 years as a consulting architect I became disabled, as a result, I am now embracing a Slow life. F…

A Word about Equipment

There are a variety of methods for roasting coffee at home using a multitude of devices. From air popcorn poppers to propane grills, each has it's own unique limitations and features. This Instructable focuses on roasting coffee at home using the Behmor 1600 Plus coffee roaster. It provides the beginner with a straightforward and reliable introduction to coffee roasting while providing enough flexibility for experienced home roasters. If you would prefer to start roasting coffee with a slightly lower initial investment, here is a fine Instructable on roasting coffee using a popcorn popper.

Roasting coffee for family and friends can be a very rewarding experience. Coffee makes a great gift, and coffee roasted at home, in small batches, will outshine even the finest store bought coffees. Later the Instructable will explain why, but for now, know that your efforts will result in something truly amazing.

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Step 1: Safety First

No matter what methods or equipment one uses to roast coffee, safety must be paramount. There are four basic safety rules to be followed at all times.

  • Have a fire extinguisher within reach at all times
  • Work in a Well Ventilated Area
  • Never leave the roaster
  • Never roast past the start of 2nd crack*

Coffee oils and chaff are flammable, and the smoke generated when coffee burns is thick and acrid. Even a half pound of coffee, if on fire, can generate enough smoke to fill a small house and irritate the eyes and lungs of everyone in it. Well ventilated in this case means directly under a range hood or in a garage, sun room, etc... If working in a basement or work room, it is possible to hang or mount an inexpensive ducted range hood over the roaster and vent it to the outside using flexible ducting.

*More on this later

Step 2: A Coffee Primer

Before diving in to the specifics of roasting coffee, an overview of what coffee roasting is and how coffee beans are processed is helpful. It is also important to know a few things about green (unroasted) coffee and how to select and purchase it. Whole books and careers have been dedicated to these subjects, but it is hoped this concise overview will be of use.

Coffee Beans

Coffee beans come from coffee cherries, which grow on variety of cultivars of small tree/shrub. The cherries are picked, the fruit removed, and the resulting beans are washed, fermented, dried and graded for sale. There are a lot of different ways this washing/fermenting/drying is accomplished. What is left are green coffee beans which are sorted by size, number of defects, etc... These beans (pictured above) are packaged into bags and lots which coffee buyers inspect and cup and eventually buy and import into the U.S.

There are two main types of coffee bean, arabica, and robusta. Arabica coffee is what most people identify as "coffee." Robusta on the other hand, is bitter, much cheaper to grow, and contains much more caffeine. Chances are the store-bought coffee you drank last had 20-30% robusta beans mixed in. Most home roasters select 100% arabica, single-origin coffee beans. This results in the most flavor and is the main reason why home roasted coffee will always taste better than store bought. Single-origin means that all the beans in a bag came from the same farm, and in many cases, the same area of the same farm. These specialty coffees represent the top 1-5% of all coffee on the planet in terms of quality and flavor. This might lead one to believe they are very expensive. However, excellent green coffee beans can be purchased for as little as $5 per pound. Compare that to ~$9 for a 12 oz bag of Pete's coffee at the grocery store.

The biggest determinate of coffee flavor is where the coffee is grown. Coffees from Central and South America tend to taste more like what American palates think of as coffee. They have brown-sugar and caramel overtones with more savory notes. Coffees from Africa tend to be brighter, with more citrusy and herbal notes. Coffee from Indonesia and nearby islands tend to have a unique flavor and heavy body that can be a bit of an acquired taste. Sumatran coffee, for example, is something one either loves, or hates, but truly should be experienced.

Altitude is also a big factor. Coffee beans grown above 1500 meters in elevation are described as "hard beans" and roast differently than beans from lower elevations due to differences in the internal structure of the beans. Learning to roast with "hard beans" from high elevations is easiest since the beans are denser and tend to absorb and react to heat more slowly. A good specialty green coffee retailer will list the elevation a coffee is grown at in addition to where it comes from. A great specialty retailer will be able to tell you the name of the farm, the farmer, and where on the farm a particular bag of beans came from.

Beginner roasters should start out selecting 5-10 lbs of hard bean coffee from a single lot from the area of the world that best suits their tastes. Roasting the same coffee many, many times is the best way to gain experience with a particular roaster, and coffee roasting in general, because the resulting flavor can be compared roast-to-roast.

So where does one buy green coffee beans? Well, green beans can be found on Amazon, or through specialty retailers such as Sweet Maria's and Coffee Bean Direct. After spending a few hundred dollars on a roaster like the Behmor, it is definitely recommend to start with a high-quality coffee from a dedicated online specialty retailer.

Step 3: A Coffee Roasting Primer

Coffee roasting is much more than simply exposing coffee beans to heat until they turn from green to brown. Once again, whole books and careers have been dedicated to coffee roasting, so what is presented here is just the tip of the iceberg.

Essentially roasting coffee means controlling three chemical processes, the first two of which involve heat and time, and the last of which involves merely time. The first process is endothermic, meaning the coffee beans absorb the
heat put out by the roasting apparatus while being tumbled to ensure even heat distribution. Once this process is complete, an exothermic process begins, during which the coffee beans release heat. Finally, a process called Strecker Degradation begins which creates amino acids and emits carbon dioxide. This begins once the coffee is cooled and can continue for days or even weeks after the coffee has been roasted. This is the second reason home roasted coffee will always taste better than store bought. Once this CO2 releasing process has stopped, the coffee begins to go stale, and this process has stopped in all store bought coffees well before reaching store shelves.

These chemical processes occur within six phases of roasting.

  • Drying Phase
  • Maillard/Carmelization Phase
  • First Crack
  • Second Crack
  • Cooling
  • Strecker Degredation

In the first phase, the Drying Phase, the beans absorb heat and start to change color from green to beige (an almost hay-like color) while they lose moisture. This typically takes 5-8 minutes, depending on the roaster being used. Once the beans have shed this initial moisture, carmelization begins (actually a Maillard reaction), this causes the beans to go from hay-colored to light brown, at this point the coffee is not quite roasted. Sometime during this Maillard Phase, the coffee beans have undergone a significant internal change and will begin to give off heat. Ultimately, these changes cause the moisture to quickly be released and the coffee beans "crack" or "pop." This stage is known as First Crack and when it first starts the coffee is light roasted. As the cracking continues, the coffee moves to medium roast as it darkens in color. All during this time the coffee beans shed "chaff" which is a paper-like coating much like the skin on a peanut. The roasting machine alters the amount of heat it puts out to accommodate this added heat from the beans. The way a coffee roaster alters the amount of heat it creates over time is known as the Roasting Profile. Basically it is just a heat vs. time curve.

First Crack eventually stops, and eventually Second Crack begins. This can happen immediately after First Crack, or after a few minutes. The best way to be sure is the sound. Second Crack is much more rapid and sounds more like popcorn popping, whereas First Crack tends to be deeper sounding and slower. At the point Second Crack starts, the coffee is entering darker roast territory. Second Crack occurs because the coffee beans internal structure is breaking in a process similar to carbonization.This is the point where risk of fire is the greatest. The beans are giving off a lot of heat, the roaster is at it's hottest, and there is lots of flammable chaff and oil present. Never roast past the start of Second Crack. Since coffee fires start suddenly and quickly, it is impossible to predict reliably at which point during Second Crack a fire will occur.

So what's the difference between medium and dark roasts (other than color)? A light to medium roast will have flavors which are much more influenced by the bean itself and it's origins. A darker roast will have flavors generated more from the roasting process than the origin of the beans.

Finally the beans cooled by either rapidly tumbling them, or dumping them into a pan where they can be stirred as they cool. At this point Strecker Degradation starts. This process creates new flavor compounds, so the coffee will taste different 5 days after roasting as opposed to 1 day. Home roasted coffee is typically at its absolute peak flavor 5-7 days after roasting.

Step 4: Time to Start Roasting

Materials/Equipment Needed:

REMINDER: Make sure you are set up in a well ventilated area with a fire extinguisher within reach

Step 5: Weigh and Load Beans

Weigh out around 15 ounces of green beans. Why 15 ounces? Since coffee is packaged in 12 ounce bags, and coffee loses weight as it loses moisture during roasting, 15 ounces should yield around 12.5 ounces of roasted coffee. This will vary by which beans you roast, but 15 ounces of hard bean coffee should rarely yield less than 12 ounces of roasted coffee.

Place the coffee into the drum according to the Behmor manual. Basically this just involves unlatching the drum and loading the beans into it, then latching it again. Be sure to give the drum a shake while holding it parallel to the floor to evenly distributed them.

Load the drum into the roaster. Be sure it is seated properly before continuing. Finally, place the chaff collector in the roaster so it butts up against the bottom and front of the drum.

Step 6: Roast

If using a vent fan, turn it on low. Using the control panel, press the "1" button (for approx. 1 pound of coffee), the "A" button (which corresponds to roast duration), and then the "P1" button (which corresponds to the heat curve). This will give us the optimal roast profile for 15 ounces of hard Sumatra beans. For other bean types, consult the following chart (which is also in the Behmor manual):

  • P1-2 All centrals, Peruvian and Colombians
    P3 Brazilians, Africans, SE Asians, Malabar, Jamaican Blue Mtn and Yauco Selecto (Puerto Rican)
  • P4-5 Kona and other low grown island coffees

Finally, press the "Light" button to turn the light on and press "Start." The drum should begin turning and the timer should begin counting down.

REMINDER: Never leave the roaster once the roast has begun! The roaster has a safety feature. Whenever the timer hits "4:30" there is 30 seconds to hit the start button or the roaster will automatically start cooling and the display will read "ERR7."

Now that the roast has started, the color changes of the beans can be noted, as well as the changing smells of the roasted coffee. Little or no smoke should be venting out of the back of the unit. After enough time has gone by, the sounds of First Crack should appear and the beans should be a nice deep brown. There should also be chaff visible on the drum. If the timer looks as though it will run out, and no sounds of First Crack have been heard, simply press the "+" button to add more time (up to the maximum allowed) and then listen for First Crack.

Once First Crack starts, press the "C" button. This will automatically set the timer to 3 minutes and 30 seconds, which should stop the roast just before Second Crack, yielding a "Full City Plus" or optimal medium/medium dark roast. You can always stop at the beginning of First Crack, or at any time between First and Second Crack. Sometimes it is fun to stop at various points to taste the resulting differences. To stop the roasting process, press the "Cool" button. If you start to hear Second Crack, regardless of what the timer shows, press the "Cool" button immediately to reduce the risk of fire.

The coffee roaster will now run through a 13 minute cooling cycle.

Step 7: Weigh and Chaff

Once the cooling cycle has finished, the coffee may be removed from the roaster. Be careful, some of the surfaces, the chaff collector, and the drum can still be hot. With the vacuum ready, open the door and remove any chaff visible. Then remove the chaff collector and vacuum up any chaff in it and on the bottom of the roaster. Finally, remove the drum and vacuum up any chaff at the back of the roaster. It is also advisable to shake and rotate the drum by hand to remove any excess chaff still in the drum. Don't try to remove it all, that would take the rest of the day!

Unlatch the drum and pour the beans into a bowl tared on the scale. For future reference, make note of how much weight the coffee lost during the roasting process.

Step 8: Bag and Share!

The coffee is now roasted and ready to be bagged. Bagging whole beans helps keep the coffee fresh, allows Strecker Degradation to continue to improve the coffee's flavor, and makes it easy to give the coffee to friends and family as gifts.

Once the coffee is bagged, seal it with a high tech, dedicated, super fancy bag sealer....also known as a clothes iron. I find mine seals bags best when set to "4" (out of 10).

You can grind the coffee before bagging it for those loved ones who don't have a grinder, but it is important to note the flavor development will be basically frozen at that point. If you are going to use a grinder for this purpose, be sure to use a conical burr grinder and follow it's instructions for grinding to the right fineness depending on how the coffee is to be brewed (fine grinds are for espresso, medium grinds are for automatic drip, and coarse grinds are for French press).

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7 years ago

wow a detailed lesson right from the start! cool! i knew nothing about single source b4, now i see the scientific side of coffee!

jpalmer-rye iii
jpalmer-rye iii

7 years ago

great instructable I actually worst coffee myself but I use in Old West popery air popper has to be the type with the heat fins and not the mesh just a less expensive alternative to the fancy at home roasters


Reply 7 years ago

My first "roaster" was a West Bend Air Crazy. I still use it for Kona. The Instructable I linked to in the introduction is a great intro to air popper coffee roasting.


7 years ago

The 'Mallard' Reaction you refer to is in fact the 'Maillard Reaction'.
Either way, thanks for the interesting information.


Reply 7 years ago

Thanks for catching that! I will update it accordingly.