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

by James Hoffmann

  Aside from a good flavour and just a little hardness, there isn’t too much else we really want in the water, but a relatively low mineral content is desirable. Manufacturers of mineral water are required to list the mineral content on the bottle and it is usually described as the total dissolved solids (TDS), or the ‘dry residue at 180°C’ (365°F).

  THE PERFECT WATER

  The Specialty Coffee Association of America (SCAA) publishes suggested guidelines for the perfect water for coffee brewing. The table below offers a summary.

  If you want to understand the quality of your domestic water supply, contact your water supply company or look on its website, as most are obliged to publish data on the content of their water. If you can’t find this information, buy a water-testing kit from a pet shop (sold to test the water in fish tanks), which will give you accurate readings of the key elements.

  CHOOSING A WATER

  All this information may seem a little overwhelming and complex, but it can be summarized as follows:

  • If you live in a soft to moderately hard water area, use tap water but filter it first to improve the taste.

  • If you live in a moderate to very hard water area, bottled water is the current best option for brewing coffee. Choose a bottled water close to the above targets; own-brand supermarket waters tend to be lower in mineral content compared to the big brand waters. While it is not ideal to recommend bottled water, if you really wish to get the best out of your coffee, you must use a water suitable for brewing.

  GUIDELINES FOR THE PERFECT WATER FOR COFFEE BREWING

  Brewing a good cup of coffee at home is a matter of preference, but an important factor to understand is the ratio of water to coffee.

  BREWING BASICS

  A key moment in the journey from crop to cup is the process of brewing. All the hard work up until this point, all the potential and deliciousness locked within the coffee can be lost by bad brewing. It is upsetting how easy it is to brew coffee badly, but understanding the basic principles can lead to better results and make the process more enjoyable.

  A coffee bean is composed mostly of cellulose – it is very similar to wood. Cellulose cannot be dissolved in water, so this is what makes up most of the spent grounds we throw away after brewing a cup of coffee. Broadly speaking, everything else that makes up the coffee bean can be dissolved in water and can end up in the cup, but not everything that we can get from the coffee tastes good.

  From the 1960s, there has been ongoing research into measuring how much of the coffee we actually want to extract for the resulting cup to taste good. If you don’t take enough from the grounds then the cup of coffee will not only be weak, but it will often also be sour and astringent. This is called ‘underextraction’. And if we take too much from the grounds then the cup of coffee will taste bitter, harsh and ashy. This is what we call ‘overextraction’.

  It is possible to calculate whether we have extracted as much as we want from the coffee. In the past this was done relatively simply: the grounds were weighed before brewing, then after brewing the spent grounds were placed in a low oven until they were completely dry. When they were weighed again, the difference in weight would indicate how much of the coffee had been extracted during the brewing process. Now a combination of a specialized refractometer and smartphone software allows us quickly to calculate how much has been extracted from the grounds. Generally it is agreed that a good cup of coffee contains 18–22 per cent by weight of the ground coffee used to brew it. The exact numbers are not important to most people at home, but understanding how to adjust different parameters to improve the cup is useful.

  STRENGTH

  This is an important term when talking about a cup of coffee, but one that has been quite widely misused. The term is commonly used on bags of coffee sold in the supermarket, and in this instance is completely inappropriate. What they are trying to communicate here is how dark the roast of the coffee is, and how intense the bitterness will be.

  The word ‘strength’ when used to describe a cup of coffee should be used in the same way it is used to describe alcoholic drinks. A beer that is four per cent strength means that four per cent of what you drink is alcohol. In the same way, a strong cup of coffee has a higher percentage of dissolved ground coffee in the hot water than a weak cup. When it comes to strength there is no right and wrong – there is only individual preference.

  There are two ways to control strength and the first and most common way is by varying the ratio of coffee to water. The more coffee used to brew a cup, the stronger the resulting cup is likely to be. When talking about brewing, we tend to describe the strength by the number of grams of coffee per litre of water, for example 60g/l. To brew a cup of coffee of this strength, you would first decide how much coffee you want to brew, for example 500ml. You would then use the ratio to calculate how much coffee to use, in this case 30g.

  The preferred ratio of coffee to water varies around the world from around 40g/l up to nearly 100g/l in Brazil and Scandinavia. Generally people find a ratio that they enjoy and they stick to it for most brew methods. I would recommend 60g/l as a starting point. Changing the coffee to water ratio is how most people at home change the strength of their brews, but it is not always the best way.

  The other way to change strength is to change the level of extraction. As we steep coffee in a French press, the water is slowly taking more and more out of the coffee, and the resulting drink is getting stronger and stronger as it brews. The challenge is to control the level of extraction so we take enough from the grounds that it tastes good, before we start to extract bitter and unpleasant flavours. Many people don’t think about changing the level of extraction when they get a poor cup of coffee, but an error of extraction can certainly lead to a disappointing cup.

  EXACT MEASUREMENTS

  Small changes in how coffee is brewed can have a big impact on taste. One of the biggest variables is how much water you use, and being consistent is one of the most important aspects of brewing. It is a good idea to put the coffee brewer on scales so you can measure exactly how much boiling water you are adding. Remember that 1ml of water weighs 1g. This will give you a lot more control and massively improve the quality and consistency of your brews. A set of simple digital scales is not expensive and many people already have one in the kitchen. While it seems a little obsessive at first, once you start brewing this way you will never want to go back.

  A set of digital scales is a worthwhile investment for anyone interested in making consistently good coffee.

  MILK, CREAM AND SUGAR

  Most people who are interested in coffee are aware that milk and sugar are considered somewhat taboo by those who work in the industry. Many people consider this a form of snobbery, and it is something of contentious point between coffee professionals and consumers.

  What is often forgotten by the professionals is that most coffee served in the world requires something to help make it more drinkable. Cheap commodity coffee that has been poorly roasted or badly brewed is often incredibly bitter and lacks any sweetness. Milk, and even more so cream, does a great job of blocking some of the bitterness, and sugar makes it more palatable. Many people get accustomed to the taste of milk and sugar in coffee and will then add them to an interesting cup of coffee brewed with care. This may cause frustration for the barista, professional roaster or a person simply passionate about great coffee.

  Excellent coffee should have its own sweetness, and instead of suppressing bitterness the milk will obscure the flavour characteristics of the coffee, hiding the work of the producer and the expression of terroir that the coffee has. I would always recommend trying a coffee before adding anything to it. If it is not sufficiently palatable as black coffee, then add milk or sugar so you enjoy the cup. However, exploring this wonderful world is extremely difficult drinking anything other than black coffee, and the investment of time and effort learning to appreciate it this way will be extremely rewarding.

  Excellent coffee sh
ould have its own sweetness, and while everyone has personal preferences when it comes to milk and sugar, it is good to try a coffee first before adding anything to it.

  THE FRENCH PRESS

  The French press, also known as a cafetière or coffee plunger, is probably the most underrated method of brewing coffee. It is cheap, easy, repeatable and just about everyone has one at home.

  Considering its name, it seems somewhat surprising to discover that the most familiar version of the French press was invented and patented by an Italian called Attilio Calimani in 1929. However, a very similar brewer had been patented first by two Frenchmen, Mayer and Delforge, in 1852.

  A French press is an infusion brewer. With most methods of brewing coffee, the water passes through the grounds. Here the water and coffee steep together, which helps produce a more uniform extraction.

  The other relatively unique aspect of the French press is the way that it filters the grounds from the brewing liquid: by using a metal mesh. Due to the relatively large holes in the mesh, more of the non-soluble material from the coffee gets into the cup. The advantage of this is you get a little of the coffee oil and some tiny suspended pieces of coffee in the cup, which gives the resulting brew a bigger, richer body and texture. The disadvantage is what puts many people off of the French press: the sludge. At the bottom of the cup you will often find a reasonable quantity of silty particles of coffee that (if accidentally drunk) are quite unpleasant and sandy in the mouth.

  The brewing method opposite is designed to achieve a great brew with the minimum amount of sludge. It requires a little more work and patience but you will be rewarded with a great cup of coffee that will give you easy access to all the unique flavours and characteristics of the bean.

  Brewing coffee in a French press results in a drink of uniform extraction. The metal mesh allows for small particles to flavour the water, creating a rich body and texture.

  THE FRENCH PRESS METHOD

  Ratio: 75g/l. I recommend a slightly higher ratio of coffee to water when using an infusion brewer if you want to produce a brew with a strength similar to a pour-over brewer.

  Grind: Medium/caster (superfine) sugar. Many people grind their beans very coarsely when brewing in a French press (see Grind Size), but I don’t think this is necessary unless your grinder produces a lot of very fine pieces and your brews quickly turn bitter.

  1 Grind the coffee just before you start brewing. Be sure to weigh the coffee first.

  2 Boil a kettle of fresh water with a low mineral content, suitable for brewing coffee.

  3 Put the ground coffee in the French press and place it on the scales. A

  4 Pour in the correct amount of water, weighing as you pour so you achieve the ratio of 75g/l. Pour relatively quickly and try to get all the coffee wet.

  5 Leave the coffee to steep for four minutes. During this time the coffee will float to the top to form a crust-like layer.

  6 After four minutes, take a large spoon and stir the crust at the top. This will cause most of the coffee to fall to the bottom of the brewer.

  7 A little foam and some floating grounds will remain on the top. Use the spoon to scoop them off and discard them. B

  8 Wait another five minutes. The coffee would be too hot to drink anyway, and leaving it in the brewer allows more and more of the coffee and fine particles to sink to the bottom.

  9 Place the mesh plunger in the top of the beaker, but do not plunge. Plunging will create turbulence, which will stir up all the silty coffee at the bottom of the pot.

  10 Pour the coffee slowly through the mesh into the cup(s). Until you get close to the bottom, this liquid will have very little silt in it. If you can resist pouring out the very last bit you will end up with a delicious, flavourful brew of coffee that has very little silt. C

  11 Allow the coffee to cool in the cup(s) a little, then enjoy.

  Many people recommend pouring out the entire pot once the brew is done, to prevent the grounds continuing to steep and start to overextract. If you follow the instructions above the coffee should not continue to brew or add negative flavours, so this is not necessary.

  POUR-OVER OR FILTER BREWERS

  The term ‘pour-over’ is used to describe a host of different brew methods. The common factor is that they brew by percolation, which means that the water passes through a bed of coffee, extracting flavour along the way. Usually there is some sort of material to filter the grounds from the resulting drink, and it can be anything from paper to cloth to a fine metal mesh.

  Simple cup-top filter brewers have probably been used since coffee brewing began but the innovations on the theme came relatively late. Only cloth filters were used originally; the invention of the paper filter is credited to a German entrepreneur, Melitta Bentz, in 1908. Now controlled by her grandchildren, the Melitta Group still sells filter papers, coffee and coffee machines today.

  The invention of paper filters encouraged the move away from the electric percolator, a terrible brewer which recirculated hot water through the grounds, brewing an incredibly bitter cup. The final death knell for the percolator was the next major innovation in drip-coffee brewing, the electric coffee machine. The invention can be credited to another German company called Wigomat. Variations on the electric filter coffee machine are still incredibly popular today, though not all produce good coffee.

  Currently there is a huge range of different brewers, brands and devices on offer, all designed to do this same job and each with its own advantages and idiosyncrasies. The good news is that the principle behind this method of brewing is universal and the technique is easily adapted to different brewers.

  THE KEY PRINCIPLES

  When coffee is brewed in this way, three variables affect the resulting cup of coffee. Unfortunately they are not independent of each other, which is why precise measurement of both coffee and water is so useful, especially if you are bleary eyed when making the coffee first thing in the morning.

  1 The grind of the coffee The finer the coffee, the more is extracted from it as the water passes through. This is because there is a greater surface area, and because water flows through finer coffee more slowly so there will be more contact time.

  2 The contact time This is not only how quickly the water flows through the coffee, but also how long it takes us to add the water. We can extend the brew time by adding the water very slowly to increase the extraction of the coffee.

  3 The amount of coffee The more coffee there is, the longer the water will take to flow through and the longer the contact time.

  To replicate a good brew, these three variables must be kept as consistent as possible. If, for example, someone reduces the amount of coffee by accident, they might assume that the reason the coffee did not brew long enough was due to the grind being wrong. If we do not pay attention, it is very easy to get confused and start to make bad coffee.

  POURING KETTLES

  When using the pour-over method to brew coffee, the rate at which you add the water plays a role in the brewing process. Pouring slowly and carefully from a standard kettle is difficult to do, and recently there has been a dramatic rise in coffee bars using special pouring kettles. These are usually placed on the stove, but electric models are available. The common factor is that the spout is very narrow, so they issue a very slow, steady stream of water on to the coffee.

  Despite their popularity in the industry, I am not convinced they are a truly worthwhile expense for the home-brewer. They do make pouring easier, but if not used properly the water can drop in temperature and prevent the coffee from brewing as well as it could. They could be viewed as an overly serious and complicated gadget when, in truth, we just want to pour water slowly over the coffee. However, if we pour at different rates on different days (something that is very easy to do) then we will get different-tasting coffee from one day to the next, which is not a good scenario.

  THE BLOOM

  This is the common practice of adding just a little water to the coffee at the start
of the brew, usually just enough to get all the coffee wet. When you add the hot water, the grounds start to release the trapped carbon dioxide and the bed of coffee will swell like dough rising. It is typical to wait 30 seconds before starting to add the rest of the brew water.

  Despite the widespread nature of this practice, there isn’t a lot of science to justify it. It might be that releasing some of the carbon dioxide helps make the coffee easier to extract, and some studies seem to support this. I think it also adds a pleasant moment in the morning coffee ritual as watching the grounds bloom is a little mesmerizing.

  When making pour-over coffee, it is common practice to add just a little water at first to allow the coffee to swell, or bloom.

  The strength of a pour-over coffee will depend on the grind size, and the timing and speed of the water flowing through it.

  POUR-OVER OR FILTER BREWERS

  Ratio: 60g/l. I recommend this as a starting point for all pour-over and filter coffee methods, but be sure to experiment to find your preference.

  Grind: Medium/caster (superfine) sugar would be suitable for brewing around 30g coffee to 500g water. You will need to grind the beans more finely if you are brewing a single cup, and more coarsely if you want to brew more (see Grind Size).

  1 Grind the coffee just before you start brewing. Be sure to weigh the coffee first.