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Revision as of 08:47, 7 August 2017 by Kyle
Espresso at its simplest is a coffee brewing method which utilizes heat and high pressure to extract flavor from ground coffee beans. While this definition may sound straightforward the actual practice of brewing a great espresso involves balancing different variables to produce the best results. Brewing a great shot of espresso is similar to a controlled experiment, where you understand the effect of each variable. This is why espresso brewing is commonly referred to as both an art and a science.
There are four main elements of espresso brewing which are going to produce the end result. They are commonly called the 4 M's of espresso brewing. The 4 M's stand for Miscela, Macinadosatore, Macchina, and Mano. Roughly translated they mean the type of coffee used, the grind and dose of the coffee, the brewing equipment, and the user. The user and the type of coffee being used are particularly important, but all four of these elements need to work together to produce good results.
Type Of Coffee
Since espresso extraction is a much more concentrated brewing method than other coffee brewing methods the quality of the bean is going really important. Espresso concentrates and amplifies the inherent flavors of the beans. Simply put, if the beans being used are poor quality, then the resulting extraction will also be poor quality. Just like any other form of cooking using quality ingredients is important for getting the best results.
When selecting a bean you will want to anticipate what flavor profile you would like and what equipment you will be brewing on. Certain espresso machines and grinders are not compatible with oily beans for example. Using fresh beans, which were only opened within the last two weeks is important. Coffee is like other food and it does deteriorate and become stale/rotten. Typically we suggest a light/medium roast that is dry, roasted within the past two weeks, and roasted dry with no excess oils. We caution against excessively dark roasted or oily beans because this roasting style is frequently used to mask flavor defects within the bean.
To maintain the freshness of the bean it's important to store them properly as well. Improper storage can cause them to deteriorate more quickly, resulting in unfavorable flavor changes and a lack of crema.
Espresso has acquired a lot of misinformation surrounding it. Connotations associated with bitterness and extreme caffeine content have caused confusion among coffee drinkers. It's time to rethink espresso!
Grind & Dose
The grind and dose of the coffee are important in controlling the extraction rate of the coffee. Your dose is going to depend on whether you are making a single, double, or triple shot, as well as the type of brewing equipment you are working with. Different machines will have portafilter baskets that accept different amounts of ground coffee. For example on a Rancilio Silvia the maximum accepted dose for a double shot is 14 grams but on a large prosumer unit such as the Expobar Brewtus IV the typical doubleshot dose is going to be about 18-20 grams. If you are unsure what a good starting dose is for your machine consult with our Technical Support or the machine's manufacturer. For the sake of consistency it's important to select one dose amount and work from there.
If you have a machine that features a brew pressure gauge and you find that even though your shot timings are correct the brew pressure is low and the coffee is weak then this is a sign you may be underdosing. Check to see what dose is appropriate for the shot size you are brewing.
Grind size is how the timing of the shot is controlled. For best results you will want a grinder that has a high degree of consistency. Consistency of the grind is particularly important in espresso brewing because it's desirable to have most of the individual coffee grinds to be similar in size. Water likes to take the path of least resistance, so when the shot pressurizes the water is going to take the easiest path through the coffee. If there are lots of grinds of all different sizes the water is going to ignore the smaller grinds and only flow around the large grinds. This will result in an uneven extraction, and is typically indicated by channeling in the coffee puck, which looks like dimples in the coffee puck.
Consistent grind will cause the water to distribute evenly across the entire coffee puck. Since all of the grinds are almost the same size there isn't a path of least resistance. There is even resistance across the entire coffee puck, which forces the water to flow through the coffee evenly.
In general the higher the quality of the espresso machine the higher quality grinder you will want to go along with it. Even a great espresso machine will not pour good shots if there is a defect in the tamp/grind. Overcompensating with one aspect of the 4 M's will not make up for another one of the aspects if it is lacking. We suggest checking with our Sales department, or the espresso machine manufacturer for suggestions of a grinder that will pair well with the espresso machine. Burr style and size, burr material, motor power and rpm, doser vs. doserless, and many other factors should all be considered.
A blade grinder will not be suitable for espresso brewing. Blade grinders produce extremely inconsistent grind; frequently large chunks will be mixed in with finer grinds and lots of powdery residue.
Once you have a grinder you will need to make some basic starting adjustments. Generally you will want to start with a grind that is a little bit finer than table sugar/sand. Please be aware that burr grinders should only be adjusted in the finer direction while the burrs are running, and should be started on a coarse setting and then slowly moved down to the espresso range. This prevents clogging in the grinder, or damage from the burrs touching each other.
Once you have your grinder set to the correct starting range, then you will need to make further adjustments to the grind size to achieve the correct shot timing. The golden rule is to pour 2 oz. in a 25 s. period. If the 2 oz. pours through in less time then the grind is too coarse and needs to be moved finer. Alternatively, if it is flowing through too slowly then the grind needs to be move more coarsely. Keep in mind that the closer you get to the correct shot timing the smaller the adjustment you should make to the grind size. A small change in the grind size at this point can make a big difference in the shot timing. This gives grinders that have infinite adjustment over stepped adjustment a clear advantage, since you can make however small/large of an adjustment you want.
Another thing to consider, especially on a new burr grinder, is that the grinder will require seasoning. You may find the grinder clogs easily at first, or is particularly sensitive to adjustments or requires frequen adjustment. This is perfectly normal and to be expect. Most manufacturers don't preseason their burrs because it significantly reduces the lifetime of the burr.
Another thing to bear in mind is that there are many factors that determine how a bean is going to grind up. The roast, bean size, bean hardness, oil content, age of the bean, and even ambient temperature/humidity have an effect. This means that your grind size is a changing variable. Regular adjustments to the grind size are to be expected to maintain the proper shot timing.
There are several categories of espresso machine which all use the general espresso extraction process of applying heat and pressure. Some machines are more geared for convenience than quality, while others are very focused on quality and controlling the process, such as prosumer machines. The important thing to consider is that each espresso machine will have its own personality, so what works on one machine won't necessarily work on another machine. There will be differences in design intent, intended use, parts quality, etc. that affect how the machine will interact with the coffee and your other equipment.
Generally the higher the quality the machine the better control the machine has over variables like temperature and pressure, producing a higher quality product. Adjustment and set up considerations will be fairly specific to the machine make and model. You can find more information about your machine on it's wiki page by locating it through our supported brands page. If you can't find specific information for your machine check with the machine's manufacturer for more detailed information.
Some of the major factors that will effect how well the machine brews are going to be brew temperature and control, brew pressure, actively heated vs. passively heated groupheads, boiler capacity and style, portafilter style, pre-infusion, and pump style. High end machines, such as prosumer units are more expensive because they provide a much higher level of control over these factors, use higher quality parts, and have less variance in their operation.
This is arguably the most important aspect of pulling a good espresso shot. The other four M's can be perfect, but if the user doesn't control the process properly then the shots will taste bad or be inconsistent. You can typically pull the best shots from machines which give you the most control - but if your technique is wrong then the machine will still produce poor quality shots. This is why prosumer, semi-automatic, and manual machines have an advantage over pressurized, super-automatic, or pod machines, since they give the user the highest level of direct control.
Distributing the coffee properly is important because it effects how evenly the water flows through the ground coffee. The simplest distribution technique is a flat swipe across the coffee, like leveling flour for baking. This changes the amount of coffee in the portafilter however and doesn't fully fill in any empty pockets in the coffee grind. This technique definitely gets the job done, but will result in some slight variation in the shots.
A more reliable method of distribution is the Stockfleth's move. This distributes the grounds in a more circular motion, and it does not involve swiping away any of the coffee, which means your coffee dose remains consistent. You can find several demonstrations of this method through a simple youtube search.
How the coffee is ground into the portafilter is important. It's preferable to grind the coffee into the right of the portafilter so that it can be distributed more evenly.
Coffee that is oily will typically cause clumping. Very dry air, or a dirty grinder can also cause static and clumping in the coffee. Clumping is not desirable because it will cause pockets of denser coffee when the coffee is tamped.
Tamping is not quite as important as many of the other factors - you can get a decent extraction without tamping at all. The major points to consider are to keep your tamping consistent, don't over tamp, and make sure your tamp is very level. A tamp that is not level will result in the brew water pouring faster from one side of the portafilter faster than the other.
Ratios & Timing
Shot timing is the best way to gauge what kind of adjustments need to be made. The easiest method to use is call the Golden Rule. This method of gauging the shot timing is a quick and dirty method, but it is very effective. There are more exacting methods, but those moethods are geared for more high level users. The Golden Rule works perfectly for beginners. Essentially the golden rule is that your shots should be extracting at a rate of about 2 oz. in 25 s.
The Golden rule applies slightly differently to different machines. For smaller semi-automatic machines you begin the 25 s. count as soon as the brew circuit is activated. On larger prosumer units you don't begin this 25 s. count until the coffee begins pouring out of the portafilter -- coffee being pouring typically after 5-7 s. after the pump is activated. This rule does not apply at all to super-automatic units because their brewing systems are significantly different.
To better understand how to properly measure the resulting shot please check out the video below. Some coffees will produce more crema than others, so that must be taken into account. This is why more experienced users will use a weight based measurement for the shot timing since it is more precise.
For weight based measurement you will use brew ratios. For this method a 1:2 ratio of dosed coffee ground weight to brewed coffee weight is used - you will stick with the 25 s. shot timing when using this ratio. For example, if you dose 20 g. into the portafilter, you want to get 40 g. of dispensed liquid in 25 s. If ratio is wrong at the end of the 25 s. then the grind needs to be adjusted. If too much liquid is dispensed the grind should be moved finer. If there is too liquid then it would need to be moved coarser.
One last consideration is personal preference. The "rules" of brewing apply only so far as they are producing the results that you want. This is where the rule of thirds is helpful. Different flavor profiles are extracted from the bean at different rates during the extraction. Sour and bright notes come through first, then the sweeter/fruity notes, and lastly the more bitter/burned notes. You can chop the first few seconds off the beginning of your shot, or stop the shot early to change the resulting flavor. Selecting a different bean will be another way to get the flavor profile you want.
Bottomless portafilter work in essentially the same way that a normal portafilter does -- they are just a handle to hold the brewing basket. The main advantages of the bottomless portafilter are that the open bottom allows the coffee to pour directly into the cup. This prevents the crema from being disturbed as much, so that any texture like tiger striping remain intact. These portafilters also typically allow for the use of a triple shot basket. Lastly, and probably the most important advantage is that it is a really useful tool for detecting defects in your shots, such as channeling or improper distribution.
Pressurized baskets and portafilter systems can be thought of as training wheels for espresso brewing. These systems add an additional layer of pressurization in addition to the coffee. These systems are good for new users, because they help compensate for defects in technique. Since these systems produce a false pressurization they will not be able to achieve the same quality shots as a normal non-pressurized shot basket. They're really meant as a learning tool - to truly master and perfect your shots you will want to graduate from these to a normal commercial style basket. Even if you are using a pressurized basket/portafilter system that does not mean you can completely ignore brewing technique. These systems simply help reduce how reactive the system is to the different brewing variable.
You can see a side by side comparison of non-pressurized vs. pressurized baskets below. The pressurized baskets will tend to produce larger bubbles, and there will be flavor differences.
Each of the 4 M's is important, but it they need to work together for the best results. Let's put the theory into practice by walking through an example situation on a Gaggia Classic.
- Before we do anything with the equipment let's select a bean. A high quality bean is important for getting a good tasting shot. For a crema rich shot something like the Lavazza Super Crema works nicely. One of the micro-roasted coffees will also work very well. Microroasted coffee is roasted under strict control conditions and are very high quality.
- We want the machine to be on and fully heated before brewing. On this machine this full heat up time is about 15 minutes.
- First we will adjust our grinder down to a grind size a little bit finer than sand as a starting point. Remember - only make adjustments while the grinder burrs are running.
- Double shots are the easiest to work with, so we'll insert the commercial double basket into the machine's portafilter.
- The doubleshot basket on this machine accepts 16 g. of coffee, so we will grind that amount into the portafilter and then use the Stockfleth's move to properly distribute the coffee in the basket. A simple flat swipe can be used, but this is less accurate because it removes some of the coffee from the basket.
- We will tamp very evenly using a 58 mm. tamper, applying 30 lbs. of pressure, and twisting the tamper as we remove it to polish the surface of the coffee.
- When the brew indicator light of the machine indicates the heating cycle is finished we'll attach the portafilter and begin the shot. We'll want to brew into a measuring shot glass, and we will start the time the same time we activate the brew button. Since this is a semi-automatic unit the timing should be started as soon as the pump is activated.
- After 25 s. we'll measure the amount of liquid volume. After 25 s. the shot volume is 3 oz. This is too much, so I will make a fairly large grind adjustment.
- After the grinder has been adjusted downward we'll want to grind a couple tablespoons of coffee through to remove the old grind size. If we don't remove these old grinds the old and new grinds will mix and cause the shot to poor incorrectly.
- We'll dose, tamp, and brew again to see our new shot timing. This time we get 2.3 oz. in 25 s. This is pretty close, but not quite right. This time we'll make a smaller grinder adjustment and then repeat the process.
- Keep repeating this process until the shot timing is correct.