Essentially all these Affogatos, Mochas or Cubanos that you order at Starbucks are just shots of coffee with add-ons – steamed or frothed milk, cream, and various flavourings.
The actual flavour of the coffee is determined by a number of factors, such as where the beans were grown, what sort of soil, how they were processed, and finally, how they were roasted.
Roasting makes the difference between a smooth, sweet coffee and a smoky, bitter brew. It releases the flavour compounds hidden in the bean, and spreads through the air the volatile chemicals that we recognise as the aroma of a good cup of coffee.
So let’s explore the whole roasting process, and understand the different types of roast that have been perfected over generations so that first sip will give you the flavour you love.
Coffee Bean or..Seed?
If you are familiar with a roasted coffee bean, you probably would not recognise a green bean in its natural state. The coffee bean is actually the seed of the coffee plant, and it grows inside a berry in a cluster similar to a bunch of grapes.
The seed inside, the coffee bean, is green, soft and spongey and before you can even think about using it to make a cup for breakfast, it has to be roasted.
The Roasting Process – What Happens
When a coffee bean is roasted, two things happen – there is a chemical change in the bean, and also a physical change.
Coffee beans are made up of many different chemical molecules and during roasting these begin to change, combine, or disappear completely. The main chemical changes that affect flavour are in the oils and acid compounds, and in the natural sugar in the bean, the key point being that at high temperatures the sweetness turns into bitterness.
Physically, the moisture in the bean turns into steam and expands until it breaks through the cell structure, creating a cracking sound – what roasters refer to as the first crack. The moisture then starts to evaporate, drying out the bean.
When all the moisture evaporates, the roaster hears a second crack, which indicates it is time to stop the roast and “pull” the beans, to prevent them over-roasting and turning into charcoal.
The 3 Main Stages in Roasting
- Drying Stage. This takes place at an average temperature around 230 degrees Celsius (450 Fahrenheit) and in this stage most of the moisture evaporates.
- Browning Stage. Evaporation continues in the second stage, where the oils, sugars and acids start to react and produce melanoid compounds that turn the bean brown, much like our skin when we are sunbathing.
- Development Stage. We hear the first crack and that signals the next stage where the aroma and flavour develops. This stage finishes at the second crack and the beans have then to be pulled to stop them from over-roasting.
By then the beans have lost about 20% of their weight. This actually means that it takes around 8 pounds (3.6 kilograms) of green beans to produce 6.4 pounds (2.9 kilograms) of roasted coffee.
Time and Temperature
Traditionally coffee roasters produce three separate types of roasted beans, based on regional tastes and general preferences. These are a light roast, a medium roast, and a dark roast. Each type has several variations, and all are produced by varying the roasting temperature and the amount of time the beans are in the development stage.
The normal temperature for commercial roasting depends on what sort of roast is required. A light roast will start at a lower temperature than that for a medium or dark roast, at around 190 degrees C (380 F), going as high as 280 C (540 F) for a dark roast, with a medium roast somewhere in between.
Naturally all professional roasters have their own methods depending on the equipment they use, but these are a rough guide.
The exact time depends on the roasting method and the volume of beans, but usually the first crack is at around 4 to 8 minutes, and the second crack at 14 to 20 minutes.
What is the Difference Between Light, Medium, and Dark Roast Coffee?
- Light roast beans have a light shade of brown with no surface oil
- Medium roast is a darker shade of brown with very little oil on beans
- Dark roast beans have dark brown color with oily surface
- Light roast has high acidity and retains most caffeine
- Medium roast has balanced flavour and acidity
- Dark roast is perfect for espresso
- Light roast has more complex, fruity taste
- Medium roast is the most preferred option in USA market
- Dark roast preferred in Europe, especially France, Italy
To give an overview and a general idea, here is a table which summarizes the comparison between each roast.
| Light | Medium | Dark | |
|---|---|---|---|
| Roast Time | To first crack | After first crack, before second | To second crack |
| Colour | Pale brown | Brown | Dark Brown |
| Flavour | Sweet, acidy, delicate | Full strength, smooth | Smoky, bitter |
| Appearance | Dry, not oily | Dry but faint oils | Shiny with oil |
| Name | Cinnamon, Blonde, White | City, Full City, American | French, Italian, Vienna |
Light Roast
A light roast is made when the process is stopped at the first crack. The lightest is known as White Roast and is produced when the roasting process is stopped before the first crack. This is obviously a bit tricky, and a competent roast master will keep taking samples of the beans to get it just right.
The usual light roast is also known as a Cinnamon roast, and a roast in between this and White roast is called a Blonde roast, in which the beans are a golden blonde colour.
Because a light roast is roasted for a shorter time it retains most of the natural sugars, and the oils and acids are retained in the bean and not fully developed, resulting in a smoother, sweeter drink. However these beans have a higher acidity level which may not agree with everyone’s stomach.
Best Type / Origin of Beans for Light Roast
Different regions around the world each produce beans more suited to certain types of roast. The best areas for growing beans suitable for light roasts are Tanzania in Africa, Costa Rica in South America, and Kona in Hawaii.
While any bean can be roasted light, these regions produce beans that have milder, more delicate flavours that tend to fade with a stronger roast. The light roast brings out floral, fruity flavours from these beans and these are some of the world’s favourite coffee beans.
Light Roast and Health
From a health viewpoint, light roasts have the most benefits for us because they have the highest levels of antioxidants and retain chlorogenic acid which has been shown to help protect our cells from damage and inflammation.
If you are concerned about your health you should definitely stick to a light roast.
Best Way to Brew Light Roast
The best way to appreciate a light roast is to brew it using a drip or pour-over method such as a Chemex. This allows the coffee grounds to slowly develop the delicate flavours, rather than the short, high pressure espresso method.
For most people who brew their own coffee, this is the preferred method and produces the clean, rich taste and fragrant aroma that we associate with home-brewed coffee.
Medium Roast
A medium roast is achieved when the beans are pulled after the first crack but before the second crack. This roast style is often known as City roast (also as Regular roast, or American roast) and actually a medium roast coffee is the most popular type among coffee drinkers in the U.S.
When the beans are roasted for a little longer, they can be described as medium – dark, known as a Full City roast. In a medium, unlike a light roast, the oils start to come through giving stronger flavours and aroma.
Best Type / Origin of Beans for Medium Roast
Most beans are suitable for medium roast, but particularly those from Asian regions such as Sumatra in Indonesia. The highly prized Jamaica Blue Mountain beans are also best in a medium roast.
Best Way to Brew Medium Roast
A medium roast works really well when used in a Cold Brew, that is ground coffee brewed in cold water over at least 12 hours. Medium roast is also suitable for French Press coffee, while it can still be brewed in a pour-over. It even works well as espresso.
Dark Roast
Beans pulled after the second crack are much darker and more oily. They have a much stronger flavour and more bitterness, with a heavy body and less acidity.
Dark roasts are generally preferred in Europe, and in fact are known variously as French, Italian and Vienna roasts.
Best Type / Origin of Beans for Dark Roast
With light and medium roasts the regions where the beans are grown is important since the lower roasting times allow more subtle flavours to come through. However a dark roast removes all the natural flavours leaving only the almost burnt flavour and oils of the roast itself.
For this reason most professional roasters avoid dark roasts for their premium beans so they will retain the characteristics of their origin.
Having said this, there are some regions that produce beans that are more suitable for dark roasts, probably because the beans have tougher cell structures and have more natural oils. These regions are Colombia, Guatemala, Brazil and India.
Best Way to Brew Dark Roast
Dark roasts are generally coarse ground to prevent over-extraction of the flavour compounds. The finer the grind, the more surface area is exposed to the hot water and the more oil and acid is extracted.
Because dark roasts have a stronger flavour and more bitterness a long contact time with hot water could result in over-extraction, resulting in a very bitter drink.
The desired shorter brewing time makes a dark roast ideal for espresso coffee, where the water is forced through the grounds in about 25 seconds.
Caffeine Levels By Roast
All beans have same amount of caffeine per bean, so how does the type of roast change the caffeine level?
The answer is not quite that simple. The longer the roast time, the more caffeine is extracted, so a light roast bean will have more caffeine than a dark roast bean.
Also, the weight of the bean is a factor.
A light roast has more moisture and more oils giving a denser, heavier bean, and the same goes for a medium compared to a dark roasted bean.
The dark roast removes just about all the moisture, making each bean lighter.
What this means is that when you judge the beans by weight, 500 grams of a light roast will have less caffeine than 500 grams of dark roast, simply because there are more beans in the dark roast.
However, by volume using a spoon or scoop the amount of caffeine in a light roast is higher than a dark, although it is easy to see why dark roasts have a reputation as being stronger due to their heavier, more bitter flavours.
Best Roast Type for Decaf
Decaf coffee used to be criticised as just brown, coffee flavoured water. But now many people are realising that the decaffeination process still retains most of the flavour compounds of the beans.
Caffeine itself has no particular flavour – it is simply a bitter chemical that plants evolved to act as an insecticide – the caffeine buzz you get is nature’s way of killing off marauding insects.
In most blind taste tests it is very difficult to differentiate between regular and decaf coffee.
Having said that, most decaf coffees tend to be on the darker side. The various processes that remove the caffeine also remove most of the moisture making the decaf beans lighter and the time between first and second crack is very short, resulting in a darker roast.
Final thoughts
Who would have guessed the world of coffee roasting is so complex, with so many different factors at play that all together determine what the end product, the cup of coffee in your hand, will taste like.
But that is exactly what makes coffee such an interesting drink and to many connoisseurs more than just a cup of joe, it is like a fine wine to be savoured and appreciated.
Anyway, whichever way you drink it, now at least you know the differences and perhaps you can begin to experiment, maybe ask your regular café what type of roast they serve.
You can even sample bags of coffee from various regions and in different roast styles in your home – but be careful, if you were not already a coffee addict, you might become one!
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