How to Roast Coffee Beans

Django Coffee: How to Roast Coffee Beans

As the legend goes coffee was discovered in the 9th century when an Ethiopian goat herd, Kaldi, witnessed the increased energy of  his goats after they had eaten the bright red fruits of the coffee plant which led to the early primitive methods of roasting such as roasting the beans in open fires or baking inside ovens. The first known dedicated coffee roasted came from Persia in the 1400's where the roasting plate was like a large perforated spoon that sat over the open fire. [1] By the 1600's cylindrical roasters were appearing in London, [1]  however  it was not until the 1800's when laws guaranteeing coffee purity and the invention of commercial coffee roasters that these archaic methods of coffee roasting moved from the home to the factory. [2]  The commercial roasters were a great technological advancement in the art of coffee roasting and enabled coffee to be roasted on a massive scale. These days the shift has returned to smaller scale roastarys  with the surge in speciality coffee,  where the emphasis is on creating quality coffee rather than coffee as a commodity. This increasing trend of speciality coffee is similar to the wine or craft beer industry where more care and attention is taken in growing and cultivating the crop in order to ensure  the quality. The Speciality Coffee Association of America (SCAA) explains that  Speciality coffees are grown in special and ideal climates, and are distinctive because of their full cup taste with little to no defects. The unique flavours and tastes are a result of the special characteristics and composition of the soils in which they are produced. [3]

Roasting is the reason why we are able to taste the coffee that we drink.  The roaster has one of the most important jobs in determining the taste of the coffee we drink. The green coffee bean is flavourless and it is only due to the roasting process that these flavours develop within the bean. Coffee has a variety of different flavours and these depend on many factors including origin, climate, varietal of green bean, altitude and of course the roasting process. Roasters are able to manipulate the heat and time of a roast to accentuate the desired taste, this is known as roast profiling and involves temperature over time. The roaster controls both the conductive and convective heat  to create different chemical reactions within the coffee beans. The roasting process is also controlled to determine the three key aspects of how coffee will taste, the acidity, sweetness and bitterness.  [4] A good roaster  will understand how the manipulation of heat will affect different beans flavour profiles. Lighter roasts  will enhance acidity and brightness and their profiles normally consist of fruit and floral aromas. Light roasts retain most of the original coffee characteristics and so you are therefore tasting the origin of the coffee. [5] Darker roasts are fully bodied and have caramel and chocolate flavour characteristics. With darker roasted coffee you are tasting the roast itself and how well the roasters has shaped the flavours. [5] They aim to develop the positive tastes and under-develop the negative tastes. Roast profiling also aids the consistency of roasts as it maps the temperature and time throughout the roast so that the same process can be followed over and over again. This also aids in providing an even roast and finding the right balance between the taste of the bean and the taste of the roast. Over roasting will burn away all the flavour and under roasting will means you will detect the  taste of the green bean. 

Coffee Roasting Process

There are five stages to the roasting process, DryingYellowingFirst CrackRoast Development and Second Crack.  Green coffee beans seem dry but due to the processes involved in in cultivated and harvesting the coffee the inside of the green beans can still be dense with water. [6]  During the Drying Process  the coffee will not brown in the presents of water so during the first few minutes the coffee remains green whilst the beans are drying out.  As the the coffee is roasted the Yellowing stage occurs where the water inside the bean begins to turn to gas and pressure begins to build up inside the walls of the beans which leads to the first crack and the beans turning a yellow colour. The First Crack is where the beans start to caramelise and where the carbon dioxide gases within the bean have built up to a point that the beans double in size and begin to lose the outer skin known as chaff. This is the stage where the familiar coffee flavours develop. [4]  The Roast Development stage is the most crucial stage for influencing the flavours. This process must be monitored closely as important physical and chemical changes are occurring by the second.  The beans become more porous and oils begin to migrate around the structure. [7] The longer coffee is roasted acidity will decrease and bitterness will slowly increase. The natural sweetness will peak between these highs of acidity and bitterness. [4] The final stage of the roasting process is the Second Crack, this stage produces the darkest roast sometimes called "Italian or French roast" This is a very short stage and many roasters will not want to roast up to the second crack as there is a high chance of bitter coffee being produce. roasting past this stage will also probably lead to fire. 

At Django Coffee Co. our current stock of coffee has a range of roasts from lightly roasted, medium and to dark. Our darkest roast is our only roast that does make it to the second crack but we feel that the profile of the coffee does warrant this. Roasting is obviously very important in order produce excellent coffee and we really enjoy experimenting with our coffees and our roasting methods in order to create our own unique flavours.