The World Atlas of Coffee: From beans to brewing - coffees explored, explained and enjoyed

by James Hoffmann

  A roaster will see a decrease in the rate at which the coffee is increasing in temperature at this point, despite the fact that they may be adding a similar amount of heat. Failure to add enough heat can stall the roast and ‘bake’ the coffee, resulting in poor cup quality.

  STAGE 4:

  ROAST DEVELOPMENT

  After the first crack stage, the beans will be much smoother on the surface but not entirely so. This stage of the roast determines the end colour of the beans and the roast degree. Here the roaster can determine the balance of acidity and bitterness in the end product as the acids in the beans are rapidly degrading while the level of bitterness is increasing as the roast continues.

  STAGE 5:

  SECOND CRACK

  At this point the beans begin to crack again, but with a quieter and snappier sound. Once you reach second crack, the oils will be driven to the surface of the coffee bean. Much of the acidity will have been lost and a new kind of flavour is developing, often referred to as the generic ‘roast’ flavour. This flavour doesn’t depend on the kind of coffee used as it is a result of essentially charring or burning the coffee, rather than working with its intrinsic flavours.

  Progressing a roast past the second crack usually results in the beans catching fire which is extremely dangerous, especially with large commercial roasting machines.

  There are terms used in coffee roasting such as ‘French Roast’ or ‘Italian Roast’. Both of these terms are used to indicate very dark roasts, typically high in body and bitterness but with many of the characteristics of the raw coffees lost. While many enjoy coffees roasted in this manner, these kinds of roasts are not suitable for exploring the flavours and characteristics of high-quality coffees from different origins.

  Coffee vendors have plied their aromatic trade for centuries, as depicted in this 18th-century engraving of a Parisian street hawker by Anne Claude Comte de Caylus.

  SUGARS IN COFFEE

  Many people talk about sweetness when describing a coffee and it is important to understand what happens to the naturally occurring sugars during roasting.

  Green coffee can contain reasonable quantities of simple sugars. Not all sugars are necessarily sweet to the taste, though simple sugars usually are. Sugars are quite reactive at roasting temperatures and, once the water has evaporated out of the bean, the sugars can begin to react to the heat in different ways. Some go through caramelization reactions, creating the caramel notes found in certain coffees. It should be noted, however, that the sugars that react this way become less sweet, and will eventually start to add bitterness. Other sugars react with the proteins in the coffee in what are known as Maillard reactions. This is an umbrella term covering the browning reactions seen in roasting a piece of meat in the oven, for example, but also when roasting cocoa or coffee.

  By the time coffee has finished the first crack stage, there are few or no simple sugars left. They will all have been involved in various reactions resulting in a huge number of aromatic compounds.

  ACIDS IN COFFEE

  Green coffee contains many different types of acids, some of which are pleasant to taste and some that are not. Of particular importance to the roaster are the chlorogenic acids (CGAs). One of the key goals of roasting is to try to react these unpleasant acids away without creating negative flavours, or driving off the desirable aromatic components of the coffee. Some other acids are stable throughout the roasting process, such as quinic acid, which can add a pleasing, clean finish to a coffee.

  AROMATIC COMPOUNDS IN COFFEE

  Most of the aromatics in a good cup of coffee are created during roasting through one of three groups of processes: Maillard reactions, caramelization and Strecker degradation, another type of chemical reaction involving amino acids. These are all brought about by the heat during roasting and can result in the creation of over eight hundred different volatile aromatic compounds that flavour the cup of coffee. Although more aromatic compounds have been recorded in coffee than in wine, an individual coffee will only have a selection of these different volatiles. That said, the smell of freshly roasted coffee is so complex that all attempts to manufacture a realistic, synthetic version of this smell have failed.

  ROAST PROFILE

  Roasters track the temperature of the coffee beans during roasting: by changing how quickly a roast progresses at different times, the roaster can alter the flavour of the final coffee.

  QUENCHING

  After roasting, the coffee must be cooled quickly to prevent over roasting or the development of negative (or ‘baked’) flavours. In small-batch roasting this is often achieved using a cooling tray, which rapidly draws air through the coffee to cool it down. With large batches of coffee, air alone is not effective enough: a mist of water is sprayed on to the coffee, and as it evaporates and turns to steam, it draws heat out of the beans. Done correctly, this has no negative effect on cup quality, but the coffee will age a little quicker. Unfortunately, however, many companies add more water than necessary to increase the weight of the beans and add monetary value to the batch. This is both unethical and bad for cup quality.

  TYPES OF COFFEE ROASTERS

  Coffee tends to be roasted close to where it will be consumed, as green coffee is more stable than roasted beans – coffee is at its best when used within a month of roasting. Roasting methods vary, but the two most commonly used types of machines are drum roasters and hot-air or fluid-bed roasters.

  DRUM ROASTERS

  Invented around the beginning of the 20th century, drum roasters are popular with craft roasters, as they are able to roast at slower speeds. A metal drum rotates above a flame, moving the coffee beans constantly during the process to aid even roasting.

  The roaster can control the gas flame, and therefore the heat being applied to the drum, and can also control the flow of air through the drum, which dictates how quickly the heat is transferred to the coffee.

  Drum roasters come in a range of different sizes, the largest being able to roast up to around 500kg (1,100lb) per batch.

  FLUID-BED ROASTERS

  Invented by Michael Sivetz in the 1970s, fluid-bed roasters tumble and heat the beans by pumping jets of hot air through the machine. Roast times are significantly shorter than in a drum roaster so the beans tend to swell a little more as a result. The higher volume of air conducts heat more quickly into the coffee, which means that this roasting process is faster than drum roasting.

  TANGENTIAL ROASTERS

  Built by a company called Probat, tangential roasters are similar to large drum roasters but they have internal shovels to mix the coffee evenly during heating, which allows a bigger batch to be roasted effectively. The capacity isn’t much larger than a very large drum roaster, but this type is able to achieve faster roasting speeds.

  CENTRIFUGAL ROASTERS

  Centrifugal roasters allow very large quantities of coffee to be roasted incredibly quickly. The coffee is placed inside a large inverted cone, which spins to draw the coffee beans up the walls as they are heated. The beans are then flung back down into the middle of the cone to repeat their journey. Roast times can be as low ninety seconds using machines like this.

  Roasting at very high speeds minimizes weight loss and increases the amount of coffee that can be extracted from the beans, which is important when making instant soluble coffee. Roasting at these speeds is not designed to produce the best possible cup.

  BUYING AND STORING COFFEE

  There is no foolproof way to ensure you get great coffee every time you buy a bag. However, there are a few points to remember, starting from when you are choosing where to shop to how you store the coffee you have bought, which will increase your chances of ending up with a very good cup of coffee.

  Most people buy their coffee in a supermarket but there are many reasons to avoid this practice, not least because of the freshness of the coffee on offer. However, perhaps the best reason to avoid buying coffee from a supermarket is because of the sheer pleasure to be found in buying fro
m a specialist shop. Small shops offer the opportunity to build a relationship with someone passionate and knowledgeable about coffee. It helps when choosing if you can get some advice and even try a coffee before you buy. Dealing with someone directly means you have a better chance of buying a coffee you’ll really enjoy, especially if you let them know what you enjoyed previously.

  STRENGTH GUIDES

  You’ll often see a strength guide on the side of a bag of coffee, especially those on offer in supermarkets. These have nothing to do with strength, which is really about how much coffee you use to brew a cup, but more to do with the level of bitterness you can expect to find in that particular coffee. This is usually determined by the roast level of the coffee – light-roasted coffees usually have lower strength ratings and dark-roasted coffees have higher strength ratings. I would avoid coffees that come with a strength rating because, more often than not (and there are exceptions), the quality and flavour of the coffee have not been the primary concern of the producer.

  TRACEABILITY

  There are thousands of different coffee roasters, and hundreds of thousands of different roasts of coffee from different farms. Not all of them can be good, and variations in price and the way they are marketed can make buying fairly confusing. This book aims to explain where coffee comes from, and how and why its origin can affect its flavour. The best advice I can give is to buy as traceable a coffee as possible.

  In many cases it is possible to find a coffee from one specific farm, or one cooperative. However, that level of traceability is not possible in every coffee-producing country in the world. Each of the sections on the different countries offers an idea of how traceable the coffees from that country can be. Much of Latin America is able to produce coffees that are traceable down to a particular small farm because most of the coffee there is grown on small private estates. In other countries small-scale land ownership by farmers is unusual, or the trade regulations of a country may interfere with the export process, making traceability difficult.

  To keep a batch of coffee traceable throughout the entire supply chain adds cost, and this investment can only be returned if the coffee is sold for a higher price. This means it is only worth keeping high-quality coffees traceable, as doing so with low-quality lots would make them uncompetitive in the market place. In an industry plagued by ethical concerns, and dogged by an image of exploitation of the Third World, knowing exactly where a coffee comes from is a powerful piece of information. As communication technology, especially around social media, spreads and develops we’re likely to see increased interaction between those who produce the coffee and those who ultimately drink it.

  The best cup of coffee begins with a well-chosen bean. Choose freshly roasted beans from a specialist shop; they should also be able to advise you about the coffee’s origins.

  GOLDEN RULES FOR FRESH COFFEE

  Everyone agrees fresh-roasted coffee is better, so I would make the following recommendations:

  1 Buy coffee that has a clear roast date on the packaging

  2 Try to buy within two weeks of roasting

  3 Buy only enough coffee for a couple of weeks at a time

  4 Buy whole beans and grind them yourself at home

  STORING COFFEE AT HOME

  Once the staling process begins, there is very little that can be done to prevent it continuing. As long as you are buying fresh coffee and using it relatively quickly the impact on your cup of coffee should be minor. However, there are ways to store coffee at home that will keep it in the best possible condition.

  1 Keep the coffee airtight If the bag can be resealed, then make sure it is kept that way. If the bag can’t be completely resealed, transfer the coffee to an airtight container, such as a plastic tub with a lid or one designed specifically for storing coffee.

  2 Keep the coffee in a dark place Light rapidly accelerates the staling of coffee, especially sunlight. If you keep your coffee in a clear container, place it inside a cardboard box.

  3 Don’t put it in the refrigerator This is a common practice, but it does not extend the life of coffee, and you can get cross-contamination of aromas if you have something particularly fragrant in the refrigerator with the coffee.

  4 Keep it dry If you can’t keep it in an airtight container, then at least avoid placing it in a humid environment.

  If you need to store some coffee for a long period of time, place it in the freezer to slow down the staling process. It is important to package it in an airtight container first. When you want to use the coffee, defrost it thoroughly first, but be sure only to defrost the amount you are planning to use straight away.

  Beans last longest when stored in an airtight container, in a dry, dark place.

  FRESHNESS

  Over the years most people have been conditioned not to think of coffee as being a fresh food product. For some it is because instant coffee is what they associate with coffee and that doesn’t really ever go stale. Coffee sold in supermarkets will often have a best-before date that is 12–24 months after the date it was roasted. This is because coffee is considered shelf stable and it is safe to consume two years after roasting, but it will taste pretty terrible at that point. It is more convenient for all involved if coffee isn’t treated like a fresh product, with the exception of the ultimate consumer.

  The speciality coffee industry has failed to make a real impact because there is no strong agreement on how quickly coffee goes stale, and at what point it will have passed its best-before date.

  I would recommend buying coffee that clearly shows the date of roasting on the label. Many coffee roasters now suggest that the coffee is used within a month of roasting and I would follow this advice. The coffee is at its most vibrant during the first few weeks and after this an increasingly unpleasant stale flavour begins to develop. Many specialist shops stock bags of coffee that were recently roasted and delivered, and buying online direct from the roaster usually ensures your coffee is delivered to your home within a few days of roasting.

  STALING

  When coffee goes stale there are two main changes occurring. The first is the slow but steady loss of aromatic compounds, the compounds that give coffee its flavour and smell. As they are volatile, these compounds slowly leach from the coffee so the older it is the less interesting it will taste.

  The second change is the staling caused by oxygen and moisture. This type of staling creates new flavours, often relatively unpleasant ones. As the coffee changes it will develop a generic stale taste, and much of its original character will be lost. Stale coffees tend to taste flat, woody and vaguely of cardboard.

  The darker the coffee has been roasted, the faster it will go stale. This is because the roasting process makes the coffee bean more porous, so it is easier for oxygen and moisture to penetrate and start the staling reactions.

  ‘RESTING’ COFFEE

  To further confuse the issue, it is quite common to see recommendations for ‘resting’ the coffee before brewing it. When coffee is roasted the chemical reactions that cause the beans to brown produce large volumes of carbon dioxide. Much of this gas remains trapped inside the beans, and slowly leaches out over time. The coffee will de-gas quite quickly in the first few days and then the rate will slow. Adding hot water to coffee will cause the gas to be released very quickly, which is why bubbles often form when coffee is brewing.

  Espresso is a brew method that takes place under a great deal of pressure, and when there is a lot of carbon dioxide in the coffee it makes the brewing process a little more difficult and can prevent the proper extraction of flavour. Many coffee shops let the coffee de-gas for anything from five to twenty days before using it to help increase their consistency when brewing. At home, I would recommend leaving a gap of at least three to four days between roasting and brewing, but waiting too long may mean that the coffee starts to stale by the time you finish the bag. With filter-coffee brewing this is not as important, but I do think coffees taste better after two to three days than imme
diately after roasting.

  PACKAGING COFFEE

  Coffee roasters have three main choices for packaging their coffee. They will make this decision based not only on the preservation of the coffee, but also on the environmental impact, cost and look of the packaging.

  UNSEALED CRAFT PACKAGING

  The coffee is packed into craft paper bags with a simple greaseproof lining to prevent any leaching of the oil from the coffee. While the bag may be rolled up at the point of sale, the coffee is still exposed to oxygen and will stale quickly. Many roasters who use this kind of packaging will emphasize the importance of freshness, often suggesting the coffee be used within seven to ten days. When they retail the coffee they must be sure that the coffee on the shelves is as fresh as possible, though this can lead to some undesirable wastage. This type of packaging is sometimes recyclable and is generally considered to have the least impact on the environment.

  SEALED FOIL PACKAGING

  Triple-ply foil bags are sealed as soon as the coffee is packed to prevent fresh air getting in, but have a valve to allow the carbon dioxide to escape. Coffee will become stale slower inside these bags, but once opened the rate of staling will increase. While packaging like this is not currently recyclable, many speciality roasters choose this option as they consider it the best compromise in terms of cost, environmental impact and freshness.