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About this Article
Written by: Alan Richardson
Written on: September 16th, 2000
Tags: food & drink, chemical engineering, mechanical engineering
Thumbnail by: MarkSweep/MarkSweep
About the Author
In Fall 2000, Alan Richardson was a Junior majoring in Computer Science and openly admitted to never having had a cup of coffee up to that time in his life.
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Volume III Issue II > The Engineering Behind the Perfect Cup of Joe
From perfecting the coffee bean preparation process to creating the various machines used to brew the java, it has taken hundreds of years of scientific knowledge and engineering to bring the process of coffee making to the state it is in today. Creating new systems for roasting coffee beans requires that many chemical and mechanical engineering issues be considered. Another area of bean preparation in which mechanical engineering has played a role is in the grinding process. Nevertheless, the area of coffee making where engineers have had the most influence is in the development of machines and systems for brewing coffee. Perhaps the most sophisticated and difficult to understand contraption ever engineered for coffee brewing is the espresso machine. The main advance in the engineering of the espresso machine came in 1961, when the first espresso machine with an electric pump was introduced. This advance allowed for the automation of coffee making. Engineering has had a huge impact on the many aspects of coffee making including, roasting, grinding, and brewing.

Introduction

Only one word hangs in the minds of millions of people when they wake up every morning: coffee. According to the Bellissimo Coffee Infogroup, 400 billion cups of coffee are consumed annually around the world, making coffee second only to water as the most popular beverage [1]. Coffee is everywhere we go, and yet, because of its prevalence in our society, many people take the drink for granted. We might be surprised to learn just how much science and engineering goes into just a single cup. Many engineering fields, from chemical to mechanical engineering, have had huge impacts on the development, preparation, and brewing techniques. From perfecting the coffee bean preparation process to creating the various machines used to brew the java, it has taken hundreds of years of scientific knowledge and engineering to bring the process of coffee making to the state it is in today.

The Background of a Bean

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F​igure 1: Roasted coffee beans.
Coffee beans, seen in Fig. 1, are actually the seeds of a cherry that grows on evergreen trees. According to African legend, coffee was first discovered in the area we know as Ethiopia by a goat herder. This man supposedly noticed that his goats were much more lively and active after eating the coffee cherries from a small tree. He tried the berries himself and found they gave him more energy [1]. As word spread about the cherry, more and more people wanted to be able to taste the fruit, but distance limited those who could actually try it. This changed when people began drying the cherries to export them to distant areas. When the cherries arrived, they would be soaked in water for reconstitution and people noticed that the water also provided some stimulation. Thus, the first coffee made was discovered by accident. This coincidence led people to the realization that soaking many seeds of the coffee cherry in water and drinking it was more effective than eating the fruit itself and much more practical for export [1]. Whether or not this legend is true, by the 1400s coffee was beginning to find wide use in Persia and had been used in Ethiopia for "timeimmemorial" [2]. Coffee was introduced to the court of Louis XIV in 1669 by a Turkish ambassador, and the beans were soon exported all over Europe, with coffee plantations being established in European colonies [3].
It may seem that very little engineering is involved in the history of coffee so far. However, in the development of processes for preparing the coffee beans for brewing science and engineering were about to have a great and unforseen role. In order to get as much flavor out of the beans as possible, it was discovered that roasting the beans was required. This practice began in Turkey [1]. Roasting brings oils inside of the bean to the surface, giving the beans their aroma. This aromatic oil, known as caffeone, consists of over 600 different chemical substances, many of which are very delicate. To extract a good flavor from the beans, the roasting process must be done so that the unstable chemicals in the caffeine are not burned away [4]. Because of the delicacy of the chemicals, it is important to have a consistent and precise process of coffee bean roasting where the beans are neither under, nor over, roasted.
Methods for roasting coffee beans have been further developed over the hundreds of years that have passed since roasting first began and this phenomenon has occurred because of science and engineering. While the original method of roasting the beans by allowing them to cook in the sun was not an efficient method of roasting, today's methods of bean preparation are much more scientific and effective.

Engineering and Preparing the Bean

When creating new systems for roasting coffee beans, there are many chemical and mechanical engineering issues that need to be considered.
The inside of the bean must be roasted just as the outside is, but the bean must not be overcooked, or it will lose its flavor. The reason why over-roasting could lessen the taste of the coffee beans was unknown to man for hundreds of years, but technology today has provided us with answers. Since the chemical substances within the bean are released during the roasting process, flavor in the bean is lost if roasted for too long. As a result, the machines invented for roasting the coffee beans must have very sensitive heat and timer sensors. Also, the beans must be cooled promptly after leaving the roasters, because if they remain hot, the ambient heat generated by the beans would continue cooking them, even while they are out of the roaster. In general, the beans are usually cooled down with water or cool air [4]. Engineers had to come up with systems to deal with all of these factors in the bean roasting process.