Roasting Coffee

The scent of freshly roasted coffee in the morning air awakens the desire for a cup of good coffee. The intoxicating smell of coffee brings back memories and sensations, and is a pleasurable experience for the true coffee lover and especially for a coffee roaster.

Historical tools used for roasting coffee date back to the 15th Century and have been found in what used to be the Ottoman Empire and Persia. Coffee beans were roasted in round metal or ceramic wok-like pans with long handles over an open fire or hot coals, stirring the beans regularly with a long ladle so that they would not burn.

The raw coffee beans need a hot environment to roast, and they need to be stirred and kept in motion to roast evenly.

The principles of roasting coffee have not changed throughout history, only the roasting equipment have evolved and grown in scale. There are still manual and small scale coffee roasters available for home use and smaller consumption, but commercial roasteries and coffee producers rely on large scale gas flame, hot air or electrical coffee roasters that can process huge batches of green beans at once.

Roasting Coffee

The taste and aroma of coffee - Green coffee beans

The coffee bean is the actual seed inside the coffee berry. The taste and aroma of the coffee bean is determined by factors of its growth environment such as the soil, the altitude, the climate, farming, and agricultural preferences, as well as by the coffee plants’ natural characteristics.

The soil and geographical impact on flavour

The environment and nature in which the coffee plant grows and thrives impact the final taste of the coffee giving it certain geographically typical aromas. The country of origin of a coffee bean gives the consumer a hint of what to expect flavourwise. Roughly coffee beans from different parts of the world can be described as following:

Central American coffee

Balanced coffees with notes of cocoa and the spiciness of dark chocolate. A fruitiness, soft sweetness and sligh acidity is detectable through the chocolaty aromas.

South American coffee

Soft and full bodied and nutty coffees with chocolaty, rich and sweet mouthfeel accompanied by a slight acidity.

African coffee

Berrylike, flowery, fresh and citrusy coffees with rich acidity. Although sweet, fragrant and sometimes almost tealike.

Indian coffee

Indian coffees are spicy and rich with low acidity. The beans have a certain smokiness and musty grassiness and earthiness to them, recalling the nature of the monsoons.

Indonesian coffee

Indonesian, or Javanese coffee is rich, full bodied and spicy with low acidity as the Indian coffees. Depending on which island the coffee bean comes from the additional aromas can vary from flowery to sweet and fruity as the tropical nature.

Hawaiian coffee

A clean, fresh and light coffee with fruity and citrusy acidity, combined with hints of brown sugar and chocolate. The Hawaiian Kona bean is one of the most expensive and exclusive coffee beans in the world due to the small crops and difficult harvest environment.

Jamaican coffee

A sophisticated, soft and balanced coffee without bitterness. Low acidity with chocolaty and nutty aromas. The Jamaica Blue Mountain is another one of the worlds’ most expensive and exclusive coffees.

Roasting Coffee

Green coffee beans

The processing of the harvested coffee bean impacts the taste

After the ripe coffee berries have been harvested it is time for the processing phase, meaning the peeling or depulping of the coffee berry to reveal the beans, washing and drying the beans before they are ready to ship to roasteries around the world.

You might have stumbled upon the terms “natural processed”, “semi-washed”, “pulped natural” and “washed” when interacting with single origin coffees and artisan coffees.

  • Natural processed: This refers to the coffee beans being processed in an organic way, meaning that the harvested coffee berries are spread out to dry in the sun on a wide drying surface. The drying coffee berries are frequently turned and “raked” to prevent rotting and mould. This process is also called “dry processed” as the coffee beans are not processed with water, rather left to dry inside the berry pulp. This processing is typical in places where water resources are scarce such as Ethiopia and parts of Brazil, but at the same time the natural process can add to costs of labour as the drying coffee beans need to be tended to. When the coffee is completely dry it is hulled to remove the dry pulp from the beans. The flavour of natural processed coffees are often described as fruity, berrylike, with hints of blueberry, strawberry or tropical fruits. The natural process gives the coffee beans a sweet aroma because there are a lot of natural sugars in the coffee berry pulp that is absorbed into the coffee bean as it dries. If the coffee beans are spoiled they may start to smell like fermentation and yeast due to the sugars present.

  • Washed: This means that the harvested coffee berries are washed with water. First the berries are soaked in water so that the unripe coffee berries float to the surface and are easily removed. Then the coffee berries are hulled mechanically to reveal the green bean from the pulp. After depulping the beans are soaked again in water to remove the sticky residue of the pulp, and then rinsed to be ready for the drying to start. The drying can take place on drying beds under the sun, indoors, or using mechanical drying. More than half of the world's coffees are processed this way because it produces a more cohesive and cleaner outcome, and even a cleaner and more consistent tasting coffee. The washing process requires investments in equipment and facilities and is therefore also a more expensive processing method.

  • Semi-washed / Pulped natural: This is a combined processing method of coffee beans where parts of the natural process and the washing process are utilised. This combined processing method is popular among single origin and specialty coffees as the processing offers the premises for a wider range of flavours and aromas of the coffee. The coffee berries are first soaked in water to remove the unripe and flawed ones. Thereafter the pulp is removed mechanically but the beans are not rinsed and washed afterwards to remove all remains of the fruit pulp. The beans are spread out to dry in the sun with remnants of pulp and sugars. This way the coffee beans do not spoil as easy as during the natural process which requires more frequent attention. The remaining sugars on the beans are absorbed giving the semi-washed or pulped natural processed coffees a sweetness and richness. This process is sometimes referred to as Honeyed or Miel processed in Central American countries due to the honey-like aroma it gives the coffee.

The processing and drying of the coffee beans has the biggest impact on the flavour of your cup of coffee besides the degree of roasting. When you want to roast your own coffee and you have an idea of what kind of aromas you want to achieve and like to have in your coffee, you need to pay attention to three things: the origin of the coffee bean, the processing method, and finally choice of roasting method and roasting degree suitable for the green coffee of your choice.

Roasting Coffee

Roasting

The third factor that impacts the final taste of the coffee in your cup is the roasting. The choice of roasting equipment and the monitoring and tweaking of the roasting process affects the taste of the finished product.

Raw green beans don’t have much taste as such besides a slight vegetal and grassy flavour. With the roasting process we want the remaining moisture of the green coffee bean to evaporate, the beans to dry and swell, start to toast and turn from a yellow to brown without charring the coffee beans. During the roasting process chemical reactions take place within the coffee bean that resembles the ripening of fruit or berries. This allows for the natural characteristic aromas and flavours to pleasantly develop as the coffee beans roast to the desired roasting degree.

Coffee roasters and roasting equipment

To roast coffee you’ll need a heat-resistant pan of some sort that can hold the beans and with room to stir them to prevent the beans from burning. Some home roasters use cast iron pans, some roast coffee on oven trays, and some in wok-pans or popcorn machines. Most importantly the beans need to be evenly stirred or turned for them to roast evenly. Roasting coffee like this at home might cause quite a lot of smoke and the beans may jump around and pop like popcorn as they start to crack. Good ventilation is a must. For the frequent home roaster there are specifically designed home roasters that regard the popping and the smoke, and these usually have a lid and a stirring function.

Check out the manual coffee roasters for home use by the American Hive Roasters

Coffee roasters used for commercial production tend to be large scale machines operating a gas flame burner and a rotating drum for the beans, or circulating hot air in a silo roasting and stirring the beans. Small artisan and mid-sized coffee roasteries usually use roasters that have a 5-30 kg capacity per roasting batch, whereas the industrial coffee roasters produce over 100 kg of roasted coffee per batch.

But regardless of the roaster size the principles are the same; you need a closed environment that is heated either with a flame or hot air to a certain temperature, the beans need to constantly be in motion to roast evenly without burning.

How to roast coffee?

You’ll need green coffee beans. You’ll need a roaster. You’ll need an idea of what kind of coffee you want to achieve. Depending on the characteristics of the green coffee you can plan what flavours and aromas you want to enhance and whether a lighter, medium or darker roast suits the coffee.

Roasting a batch of coffee takes approximately 10-20 minutes regardless of the roaster. The duration of the roast determines the roast degree. The shorter the roasting time the lighter the roast, and the longer the roast the darker the coffee.

The roasting temperature generally varies between 200-250 degrees celsius. The temperature varies depending on the batch size, i.e. the larger the bean batch the higher the temperature required at the start of the roast when the green beans are dispatched into the roaster. The coffee roaster is thus pre-heated to the desired starting temperature. The heat decreases momentarily as the green beans enter the roaster, but as the roasting process progresses the temperature starts to rise again slowly. Before reaching the desired end temperature the coffee beans need to go through the first crack stage that usually occurs around 196 degrees celsius. This is the point where the coffee bean has already turned brown and dry, and the cracking comes from the expanding and swelling reaction of the bean. After the first crack the coffee bean is basically “done” and drinkable, but it is after this first crack that the fine tuning and tweaking takes place in order to get the desired flavour profile and roast degree. This phase demands attention to detail and sensitive smell, sight and hearing. The roaster needs to be careful not to burn the beans and also not to “bake” the beans too long in a temperature too low. In both cases the coffee will lose its flavours and just taste charred or flat. The beans go through a second crack when the coffee is already dark roasted. Light and medium roasted coffees rarely hit the second crack.

The term roasting profile refers to the specific pattern of roasting a batch, in other words a recipe for roasting a certain type of coffee. A roasting profile determines the initial roasting temperature for a particular amount of green coffee, an estimated target time for roasting the batch, and the end temperature that indicates when the coffee is ready and when to empty the batch into the cooling tray. In a roasting profile roasters also document the estimated time and temperature for the first crack and possible tweaks to the heat that need to be applied, for example raising the heat at a certain time during the roast. Roasting profiles or recipes are based on the roasters’ own test runs, experience and cuppings (coffee tasting).

So, when your coffee has reached the desired roast degree and temperature, the roasting is interrupted and ended by emptying the hot coffee beans into a cooling tray circulating cool air in order to break the roasting process as fast as possible. It’s recommended to cool down the beans to a temperature under 40 degrees celsius within five minutes so that the flavours of the coffee won’t be affected. If a coffee is cooled down too slowly a slightly baked and breadlike taste might develop as a result.

Freshly roasted coffee needs to be left to rest for 5-14 days before brewing coffee. The flavours and aromas continue to deepen within the beans even after the roast and the taste of the coffee becomes more defined. Freshly roasted beans evaporate plenty of CO2 which is the reason behind the valve in modern coffee packages. If you grind and brew coffee from a batch roasted the same day the CO2 may give it an acidic and bitter savour.

Roasting Coffee

Roasting degree

We have probably all heard coffee describes as light roast, medium roast or dark roasted. But what does it really mean?

Light roast

A light roasted coffee has just passed the first crack phase and reached a roasting point where most of the moisture has been forced out of the bean and gotten a toasted light brown or golden brown colour. The surface of the bean is dry and the coffee is roasted just enough for brewing coffee. A light roasted coffee contains more acidity than a darker roast, and a light roasted coffee can have a tealike mouthfeel. In light roast coffees the berrylike, fruity and citrusy notes are notably present. Many Arabica beans and especially more rare single origin coffees are roasted lightly or to a medium roast in order to preserve as many of the natural characteristics of the bean as possible.

Medium roast

A medium roast coffee has had the time to develop a chocolate brown colour after the first crack, and the sugars within the bean have started to caramelise. The oils within the coffee beans also start to emerge to the surface giving the coffee a fuller and thicker mouthfeel. A medium roasted coffee is rich and full with hints of acidity present through a toasty taste.

Dark roast

Dark roasted coffee is roasted past the first crack and even past the slightly more subtle second crack. The coffee bean has turned a deep dark brown and the surface is glossy from the oils and caramelised sugars. When the roast is prolonged the sweetness starts to turn into a bitterness similar to the taste in dark chocolate. The taste of the coffee is toasty, rich and strong with no or very little acidity. Berrylike and fruity aromas are no longer very dominant. In a cup of very dark roasted coffee you can often see the reflections of the oils on the surface.

How to roast coffee at home

Coffee was mostly roasted in the homes in the beginning of the 20th century using manual roasters and pans. Commercial coffee roasting and production began after the first World War as larger scale industrial coffee roasters were invented. From that on roasted coffee became a commodity and home roasting became rarer.

But because the art and craft of doing things yourself nowadays is popular again and even trendy, more coffee enthusiasts have started to roast green beans at home again. The coffee craftsperson might roast coffee manually with traditional equipment, but nowadays there are also multiple smaller electrical home roasters available that can roast up to half a kilo of coffee per batch, and with technical features that allow the roaster to save roasting profiles for consistent roasting.

Behmor 2020SR Plus coffee roaster

The Behmor 2020SR is the first award-winning home coffee bean roaster that enables craft coffee roasting to be experienced at home, taking up to 454 grams of green coffee beans to the second crack without emitting visible smoke through the use of patent pending smoke suppression technology. It is the only small capacity roaster in the world manufactured with a variable speed motor to properly agitate beans, allowing for more efficient cooling and chaff removal. The Behmor coffee roaster is an easy to use coffee roaster that allows the user to utilize pre-programmed roast profiles or manually control the roast parameters.

The advantage of roasting coffee at home lies in the fact that buying green coffee beans is cheaper than readily roasted coffee, and the green beans preserve longer and better than vacuum-packed roasted ones. Green beans preserve in room temperature, away from sunlight and preferably in a dark environment, even longer than 12 months, whereas a roasted coffee can lose its flavour and aroma in a couple of weeks when stored improperly. So if you want to start roasting coffee at home, you can buy a larger amount of green beans at once and then roast smaller batches in relation to your consumption.

Order green beans from us. Our coffee selection includes unroasted coffee beans for making artisan coffee.

Roasting Coffee

Coffee roasters for home use

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