Coffee Roasting
The art and science of the perfect roast...
On this page…
1. Intro
2. Roasting Tips
3. Roasting Process
4. Levels of Roast
5. Equipment
6. Home Roasting
7. Related Reading
Coffee Search…
Can't find what you're looking for? Find it here!
Drum Coffee Roaster
Before roasting, the dried coffee bean is green and without scent. In order to develop the wonderful coffee flavor and aroma, the coffee bean needs to be roasted. The roasting process caramelizes the bean sugars and releases the coffee oils, chemically changing the bean from green and unappetizing, to shiny, brown and fragrant.
Coffee Roasting Tips
The art of roasting coffee involves evaluating the coffee in three ways:
- Look - the appearance of the bean will change through the roasting process. Its color, size and texture should be watched carefully.
- Listen - two distinct popping sessions are heard during coffee roasting. These are known as the first and second 'crack'.
- Smell - the beans will smell differently at each stage of the roasting process. The aroma should be used in conjunction with appearance of the bean to evaluate the stage of the roast.
Some coffee roasting terminology:
- Endothermic - coffee bean is absorbing heat. This occurs as the beans change colour.
- Exothermic - coffee bean is releasing heat. This occurs during the first and second 'crack'.
To note:
- Beans will continue to roast under their own heat and may end up burnt if you do not cool them immediately after roasting. Some home coffee roasting machines will do this for you.
- The time it takes to roast coffee depends on the roasting method and the degree of the roast. The times shown below are approximate. It is normal for home roasting to take anywhere from 10 to 20 minutes.
The Coffee Roasting Process
Stage 1 - Green-to-Yellow (Approx. 3-5 minutes)
During this first stage of coffee roasting, the beans will turn from green, to pale-yellow, to yellow. As the beans turn yellow, you will notice steam escaping from the beans as the heat causes them to lose water. You will also notice a grassy, or hay-like smell.
Stage 2 - Yellow-to-Brown (Approx. 5-9 minutes)
The next stage sees the beans turn from yellow, to light-brown, to golden-brown. As this happens, the beans will take on a mottled/marbled appearance and the quantity of escaping steam will begin to reduce. The aroma will begin to smell toasted, like toasted wheat, or bread. The beans will appear wrinkled, but this will change as the groove in the coffee bean will open slightly as the bean expands from the heat.
Stage 3 - The First Crack (Approx. 10-11 minutes)
Sounding rather like popcorn popping, the first crack occurs as the beans expand. The grooves in the coffee beans open and as the beans expand (up to double their original size), the surface of the beans appear more smooth, losing the marbled/wrinkled appearance of stage 2. The aroma is now a familiar coffee fragrance, rather than grassy or toasty.
The beans now appear golden-brown and smooth. At this stage, you can consider your beans roasted. Some beans will suit such a light roast as this - known as a Cinnamon roast.
If you stop the coffee roasting process at this stage, the beans will retain much of their origin characteristics and their origin traits will not be masked by the roast characteristics.
Stage 4 - Coffee Roasting by Degree (Approx. 11-14 minutes)
During the next 3 or 4 minutes, as the sugars in the beans caramelize further and the coffee oils are released, the beans will turn progressively darker shades of brown and appear more oily/shiny. The beans may be removed at any time during this stage to suit the roaster's preference for the bean.
As the roast progresses, the characteristics of the roast will begin to mask the characteristics of the bean. This may be desirable, or undesirable, depending on the quality and origin of the green beans.
Stage 5 - The Second Crack (Approx. 15 minutes)
Sounding more like a snap than a pop, the second crack marks the end of the sugar caramelization, and the beginning of sugar burning. Most espresso roasts are stopped just as the second crack begins. This stage occurs very quickly and you should bear in mind that the coffee will continue to cook under its own heat unless you cool it immediately. Some common roasts are named as follows:
Full City Roast = second crack is just beginning (~10 seconds)
Vienna / Light French Roast = second crack is underway
Full French Roast = second crack ending (rapid popping)
After the second crack begins, the flavor and characteristics of the roast will override any characteristics from the origin of the bean.
Degrees / Levels of Roast
Roasts vary from light-caramel in color, to dark-brown, almost black. When beans are under-roasted, coffee is light in color (or colorless) and has an astringent taste. When over-roasted, coffee is bitter and tastes of charcoal.
Each of the levels of roast listed below can be used for any method of coffee making, with the exception of espresso, for which you should use only a dark, or very-dark roast.
The light, or pale roast should only be used with very high quality coffee. This is because the lighter the roast, the more of the coffee traits you will taste in the cup. A light roast will mask none of the coffee's origin traits.
High quality coffees, with their agreeable acidity, benefit from the light or medium roasts and generally taste good with milk. The darker roasts should be served black.
Levels of Roasts:
| |
Other Names |
Color |
Lustre |
Taste |
Light |
Cinnamon Roast |
Pale-brown |
None |
Sharp, acidic |
Medium |
American Roast,
city roast |
Brown |
Mild |
Bittersweet tang |
Dark |
Continental Roast,
Viennese Roast |
Dark-brown |
Shiny |
Smoky |
Vary Dark |
French Roast,
New Orleans Roast,
Full Roast |
Almost black |
Glossy |
Smoky, rich |
Methods of Coffee Roasting and Equipment
Methods of roasting coffee vary from very simple to highly technical. At the simple end, there is basic pan/stovetop and oven roasting. In between, there are home air-poppers and home drum roasters. At the technical end, there are many types of commercial roasters will all the 'bell and whistles' you could imagine.
The two most common types of home coffee roasting equipment are:
1. Hot Air Roasters (Popcorn Poppers):
Also known as fluid-bed roasters, these machines roast the coffee on a stream of hot air. The entire process takes less than 10 minutes and the results are more than satisfactory.
Examples of hot-air roasters (click to buy):
Electric hot air popcorn popping machines use the same principle as fluid-bed roasters. Some people use these machines for roasting coffee.
2. Drum Roasters:
Drum machines tumble the beans to roast them evenly, tumbling them in the heated drum for the duration of the roast.
Home drum roasters make coffee roasting possible in your own home without too much fuss. They come with full instructions and are easy to use.
Example of a drum roaster (click to buy):
Home Coffee Roasting
For detailed guides on how to do your own coffee roasting at home, we can't outdo Sweet Maria's guides as a great resource.
Related reading …
Click for more about acidity, body, aroma and flavor.
Click for more about coffee blends and single origin coffee.
Click for more about coffee beans by region.
Sweet Maria's has a wonderful article with photos of the different degrees of coffee roasting.
Latest roasting articles from INeedCoffee
coffee roasting , roasting coffee , coffee roasting |
