Coffee roasting has a long, in depth, history, and it's progress towards better quality goes hand in hand with better farming and brewing techniques. This crucial middle step determines how much of the quality you preserve from farming, in preperation for a brewing techinque which extracts all the desirable aromatic compounds. The art of coffee roasting is still evolving today, and the coffee community remains humble on testing new principles which get the best out of coffee. Let's explore the major breakthroughs in coffee roasting, and hopefully indentify a trend of what the future holds!
Roasting Coffee in Pans
Whilst the origins of coffee roasting remain scarce, the safest assumption is during the 15th century in Ethiopia, coffee was roasted on pans over an open flame. Legend has it that goats who ate cherries from the tree became so energetic that they couldn’t sleep. After these findings, a goat herder named Kaldi shared these cherries with monks, some of home threw them on the fire which cooked the seeds to release delicious pleasing aromas. There's no way to validate this claim, so either by chaos or curious experimenting, coffee as we know it in a basic sense, was born into the world!
Roasting this way presents a myriad of challenges... Firstly, heat is being applied almost exclusively by conduction, as opposed to what happens now with predominantly convection heating. Additionally, there is no precise control over how much heat is applied underneath, and how much airflow to apply. The results tend to be uneven heat distubution into the seeds, resulting in an uneven roast with some coffee beans far darker than others (see above!). You will have achieved some taste of what we know as 'coffee' but unfortunately packed with all sorts of carbonised, tyre like, and burnt qualities in the brew.
This was the primary and only known method of coffee roasting for a few hundred years whilst coffee made it's way from Ethiopia to port Mocha in Yemen, and throughout the Ottoman Empire.
The Cylindrical Coffee Roaster
Coffee roasting left much room to be desired. The first major iteration over pan roasting is the cylindrical coffee roaster, which forms the basis for many drum roasters today. This design allows for a greater ratio of heat transfrer to be done by convection over conduction. Resulting in better even heat transfer to penetrate and evenly cook each seed. These old devices come in many shapes and sizes, and if your lucky, you can pick one up as an antique of the past!
Cylindrical coffee roasters grew alongside the global coffee boom in the 17th century, and whilst certainly an improvement over pan roasting, there was still a yearning to achieve even greater quality and quantity of coffee roasts. Coffee at this time was not delivered to stores pre roasted, meaning it was fairly common for people to roast at home, or in the community village hall.
Industrialised Coffee Roaster
The industrial revolution brought radical technological transformations in several industries including coffee! Many patents were being brought in a for a variety of roasters by the likes of The Probat Company, Richard Evans, Jabez Burns whom designed new features like far larger drums, airflow control and gas supply. All of which delivered coffee in larger quantities, without woody or smokey flavours that would have previously come from coal and wood burning as fuel.
The wide variety of new design features paved the way for the development of the drum roasters, and finally gave coffee a breathe of new life to be roasted consisitenly with far less defects than former methods. This went in tangent with new brewing methods like the French Press, Syphon and percolator which saw a noticable improvement in brewing quality.
Electricity & Modern Innovations
The 20th century saw further innovations like electric motors fitted in coffee roasters, this reduced any excess labour, and gave a consistent heat source more stable than a flame. Further iterations in the 1970s saw the advances on fluid buid roasters, and entirely new design which roasted coffee predominantly by convection. The design was patented by American chemical engineer Michael Sivetz in 1976.
The modern era of coffee roasting offers so many mind boggling options, but for simplicities sake, the classic drum roaster design remains the popular choice for being cost-effective and producing exceptional roasts of coffee. Core designs like the drum and fluid bed cofffee roasters, amongst several new design types, are being iterated and tweaked to give roasters better workflow in their day to day work.
Whilst the practice of coffee roasting has taken great leaps forward over several hundred years, the theory of coffee roasting has only recently come into play starting around the 90s with the Roasters Guild, formed as part of the Speciality Coffee Association of America (SCAA), the roasters guild writes 'The Town Hall Breakfast at the 1994 SCAA Conference is where Schoenholt begins his story. During the open discussion, specialty roasters stepped to the microphone to decry the lack of a Roasters Track at the conference. This is the precursor to what would become the Roasters Guild.'
This would mark the start of the coffee roasting community sharing ideas on a new science of cooking green coffee seeds in the best, most consistent way. Whilst coffee roasting manufacturers provided manuals and general guidelines on roasting coffee, so many variables can affect a roast like ambient temperatures, characterstics of different coffee seeds, how pre-heated the roaster is, and many more. The chaos of anecdotes on online coffee forums left room for a more objective look. The key was to establish underlying principles which work when tested, time and time again.
Whilst there were several books on coffee in general which may have had a chapter on coffee roasting, it rarely remained a sole topic to explore. Looking online in the 00s, you could find several videos, blogs and forums which address some of the fundamentals of coffee roasting, but it wasnt until Scott Rao's The Coffee Roaster's Companion, published in 2014, made a strong push towards an objective science based criteria for roasting great coffee. Scott Rao, The Roasters Guild, and many coffee experts are in unison that this is still a new frontier, and much work still must be done to improve the theoretical framework.
Whilst the practical aspect of coffee roasting machines has never been better, the other half of theory is still catching up! Why invest thousands of pounds into a new Giesen machine, when the machine operator is the bottleneck? Coffee roasters are constantly training so they can get the best their roasting machine has to offer! A well trained roaster on a low grade roasting machine, will do better than a poorly trained roaster on a state of the art Giesen machine!
