Convection Coffee Roasting Explained |
 Print this page
|
the convection coffee roasting
process explained
The art of coffee roasting began in the Ottoman Empire during the fifteenth century. The rich, tantalising flavours that the process created from the raw, green coffee beans quickly gained attention, and coffee has remained popular ever since. Over the centuries, different types of beans and techniques have been developed, ensuring roast coffee has many distinctive blends and tastes. However, one of the most successful methods is convection roasting.
Convection Roasting vs Conductive Drum Roasting
There is a noticeable difference between the traditional, conductive method of roasting coffee and the convection method that has been popular since the late twentieth century.
Conductive Roasting
Similar to stir-frying, the green coffee beans are tossed about in a large frying pan. Commercial roasters follow the same principle by continually turning the beans in a metal drum, and this is the process by which most roast coffee on the market is produced. As the beans land on the hot surface of the pan or drum, the direct heat transference cooks the beans on the exterior. The heat gradually moves inwards to finally roast the beans' centres.
VS
Convection Roasting
This technique is similar to baking as it uses hot air to surround the beans with warmth. It has the opposite effect to the traditional method. The hot air encourages heat to build up in the centre of the beans. It then slowly radiates out to the exterior, roasting the beans from within.
What Are The Benefits Of Convection Roasted Coffee?
There are many benefits when using the convection method to roast coffee. You'll find the flavour it produces is generally smooth and remarkably consistent across different batches of beans. The comparatively low temperature of convection roasting reaches approximately 260°C (500°F) and has a gentle effect on the coffee. As it slowly roasts the entire coffee bean from the interior, it encourages enticing, aromatic flavours to fully develop.
Any moisture within the green beans is released at a measured rate. This helps the beans to acquire a rich, caramelised flavour. In commercial machines, the fan-based, hot air flow conveniently removes the delicate outer skins or chaff, preventing any possibility of them adding a charred, burnt flavour. In general, conduction roasted coffee is reliably even, smooth and mellow.
The Issue With Traditional Conductive Roasting
Traditional conductive roasting has always relied on the skill of the cook to accurately gauge when the coffee beans are perfectly roasted. The procedure uses extremely high temperatures of up to 430°C (800°F), which often burns and scorches the exterior of the beans. Even though the beans appear fully roasted, the interior of the beans may often still be uncooked. Too much rawness can give the coffee a sour, grassy taste.
In modern commercial facilities that use conductive roasting. The high levels of heat and movement can often cause the beans to suddenly release a burst of excessive moisture that disrupts the caramelisation process. This can result in an unpleasant bitter flavour. The coffee beans might sometimes acquire additional charring as the lightweight outer skins burn when becoming trapped amongst the beans.
The Convection Coffee Roasting Process
Convection roasting follows the same procedure, whether the beans are in a small commercial roaster or a large industrial machine. It's a fascinating procedure that transforms dull, green seeds into glossy, aromatic beans.
1. Preparation
The small, green coffee beans are rinsed thoroughly under clean running water to remove dust and plant debris. The beans may absorb a small amount of water, but it helps to prevent them becoming brittle during roasting. They are then placed in the roaster where they are subjected to a constant supply of hot air of up to 260°C (500°F).
2. Roasting
After approximately five minutes, the beans begin to change colour and acquire a yellow hue. The moisture that is naturally present in the beans is slowly released as steam. Individual beans crack open as their yellow colouring gradually deepens to brown. This signals the start of caramelisation as the natural sugar within the beans begins to cook.
3. Development
The length of roasting time or development depends on the intensity of flavour that's required.
Light Roast
A light or city roast of around eight minutes produces pale brown beans with a mild aroma. It typically retains just a hint of the refreshing, grassy flavour of the raw beans.
Medium Roast
A medium roast takes around ten to twelve minutes. As the beans' sugar content continues to caramelise, they gain a slightly darker colour. Medium roasts frequently develop flavours that are unique to the geographic location where the beans were grown.
French Roast
Beans roasted for around twenty minutes usually appear very dark brown. Often referred to as a French roast, the longer cooking time makes the consistency of the beans lightweight and less dense, causing them to expand in size. Caramelisation has to be carefully monitored to prevent the sugar from burning. As fully roasted beans, they make a rich, aromatic coffee with an intense flavour.
Spanish, Italian and Neapolitan Roasts
Extending the roasting time until caramelisation produces burnt sugar results in black, oily beans. The scorched, deep and slightly flavour is typical of many Spanish, Italian or Neapolitan roast coffees.
4. Cooling
Once roasting is complete, the coffee should be cooled to room temperature as quickly as possible. Allowing the beans to remain warm for too long impairs their flavour. To keep the authentic, fresh flavour of the roast, the beans should be transferred to a glass jar.
5. Storage
When it has been roasted and cooled, roast coffee is packaged to seal in the delicious taste and aromas ready to be dispatched to customers. You should ideally get coffee as freshly roasted as possible, and store it in an airtight container in a cool, dark cupboard out of direct sunlight. Never store it in the refrigerator as the low temperature encourages it to absorb the flavours of other foods. Freshly roasted coffee should be enjoyed within two to four weeks.
For those who prefer to roast their own; raw, green coffee beans can be safely stored in an airtight container for up to twelve months without any loss of characteristic flavour. The exact taste of roast coffee usually depends on the variety of the beans and where they were grown.
Where is Coffee Grown?
Coffee cultivation is believed to have originated in Ethiopia around 800 AD. Coffee trees are now grown around the world in the 'coffee belt' between the Tropics of Cancer and Capricorn. Suitable locations include Central America, Brazil, Kenya, India and Indonesia. The evergreen trees flourish in temperatures ranging from 64°–73°F (18°C–24°C). They are often grown at high altitude, where the local soil and humidity can influence their flavour.
Which Beans are the Best for Coffee Roasting?
Two coffee seeds are found inside each of the small, cherry-like fruits that grow in clusters on the branches. They are harvested from two main varieties, Arabica (Coffea Arabica) and Robusta (Coffea Canephora).
Arabica Beans
The highest quality coffee bean is Arabica. It originated in Ethiopia, but is now widely grown throughout the world. The cultivation of Arabica beans is similar to the wine industry as the flavour of the coffee seeds is affected by the location and climate where they have been grown. Arabica coffee is generally smooth and sweet with subtle flavours of fruit, chocolate and honey.
Robusta
In the late nineteenth century, the Robusta variety was found growing wild in Congo, Central Africa. It has proven to be far more resilient and easy to grow than Arabica, making it less expensive. However, the seeds contain less sugar, resulting in roast coffee that has a tendency to taste earthy and bitter. Robusta often includes flavours resembling dark chocolate, oats and peanuts.
Does all Roast Coffee Contain Caffeine?
Coffee beans are linked with a number of health benefits; they’re rich in potassium, which is essential for a healthy heart, nerves and muscles. However, they also contain caffeine, a naturally occurring element of the coffee bean. It provides that essential energising boost whenever you drink coffee.
Caffeine helps to revive and refresh, but shouldn't be drunk in quantities exceeding 400 mg per day. The average cup of coffee holding approximately 237 millilitres (8 fluid ounces) contains between 80 and 100 mg of caffeine.
A mug of coffee measuring around 350 millilitres (12 fluid ounces) contains up to 150 mg of caffeine. All types of roast coffee have similar levels of caffeine, although darker roasts may contain slightly less. To make decaffeinated coffee, the beans can either be soaked in solvents to draw out the caffeine, or soaked with water which then passes through activated carbon to capture the caffeine, which is known as the Swiss water method and is considered a more natural way to produce decaffeinated coffee beans.
Why Choose Convection Roasted Coffee?
Worldwide, an estimated 2.56 billion cups of coffee are enjoyed every day. Less expensive roast coffees often contain Robusta beans. When you choose Arabica beans roasted by convection, you'll be amazed at the smooth, mellow quality of the coffee.
There is an impressive variety of finely-tuned roasts with individual characteristics influenced by geographic location and climate. Convection roasted beans usually produce superior light to dark coffees to suit your own particular taste.
At PureGusto we carefully select the finest beans from around the world and use convection roasting to produce coffee with incredible flavour. Our coffee has won 23 Great Taste Awards, so if you appreciate a smooth, great tasting cup then our range of wholesale coffee beans and ground filter coffee comes highly recommended.