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Myths and legends of espresso:let's demystify crema

Among the various factors for the selection of a coffee, the crema is undoubtedly an element which returns regularly. Although a crema can be pleasant, it is interesting to dwell on what explains its presence and, above all, this question: does it mean a better espresso Learn a little more about beliefs and reality surrounding this aspect of coffee..

The word crema comes from Italian and refers to the natural foam that forms on top of your coffee when you extract an espresso.o.

How is crema formed?

During the extraction process of an espresso machine, water is circulated under very high pressure, which dissolves more carbon dioxide, a gas produced when the coffee bean is roasted. When the infused liquid returns to normal atmospheric pressure, on its descent towards the cup, it can no longer cling to all the gas, so it turns into microbubbles. These tiny bubbles get stuck in the liquid and appear as a dense foam.1

So, crema is the result of two factors:

The freshness of coffee . The longer the time between roasting and brewing, the less carbon dioxide, the gas produced by the roasting, in the beans, because it evaporates. Result: less foam will form. That said, be careful! If you consume too freshly roasted coffee, it will still taste very much like gas.(See article on freshness)

A stronger coffee . The darker the crema, the stronger the coffee. As the crema is the result of the foaming liquid, it is lighter due to the way the bubbles refract light. Thus, the color of the coffee influences the color of the crema. Longer roasted coffee is darker, so produces a dark crema, but it also contains more carbon dioxide, so more bubbles.s.

It is wrong to say that crema is used to validate whether your coffee beans are of good quality, whether they have been roasted well or whether your equipment is clean, all of which are the determining factors for a good espresso.

Nespresso, champion of crema?

A marketing element widely used by the Nespresso Company, the foam produced by their devices is not an actual crema. It is a foam produced by a mechanism that generates high air pressure to create the thick foam popularized by the brand. The technical composition of the Nespresso machine means that it does not have the capacity to produce a real crema. It lacks the blend of oils from the coffee bean that a professional espresso machine processes during extraction, so that flavor is lacking in the foam produced.2  In addition, since the aluminum capsules are 100% airtight, no gas escapes, so there is a lot of carbon dioxide. Nespresso foam is a compromise for regular coffee drinkers, but it cannot be compared to that of an espresso produced by a professional machine, an authentic frothy emulsion including coffee oils. Nespresso machines just don't have the squeezing power to create real crema.3

The key elements for a good espresso, apart from the choice of coffee, are:

  • The recipe or the ratio (quantity of ground coffee per quantity of liquid to be produced);
  • The quality of the water and its temperature at extraction;
  • The grind (size of the ground grain).
  • The extraction
The goal with an espresso extraction is for the machine to produce the desired amount of liquid in a given period of time. To achieve this goal, it is necessary to control the rate at which water will pass through the grind. The speed at which the water passes through the coffee determines the flavors that are extracted from it. The first elements of the extracted coffee are acids and salts (first 1/3 of the brewing time). The second elements are sugars. These are extracted during the last 2/3 of the brewing time. The last are the bitter agents, eliminated at the very end of the infusion.4 Thus, if the water passes too slowly, your infusion will be over-extracted, offering a very dark or even absent crema, with a bitter, almost ashy taste. Conversely, if the water passes too quickly, the flavors of the coffee are not sufficiently extracted (under-extracted), resulting in a very pale crema and a very sour, astringent and weak taste.

The way to control the speed at which water passes through the grind is to change the fluidity with which it passes through. To do this, you must adjust the amount of coffee used and the size of the coffee particles. The finer the coffee is ground, the more the particles can stick together, making it more difficult for water to pass between these particles.

If your espresso tastes bad, however, it is difficult to identify whether the problem is with the size of the grind or the quantity. It is for this reason that it is strongly recommended to measure your quantity of coffee before each extraction, this factor will be validated from the start.

Pressure

The coffee bean is dense and fickle. If we were to put uncompressed coffee into the machine, the high pressure water would find the air pockets in the coffee grounds and pass through them quickly, skipping a lot of the coffee. It is for this reason that some machines like theGaggia Classic Pro offer two filter holders, one of which is pressurized. This ensures that extra pressure is applied during extraction, so you do not need to control the pressure yourself with a coffee press before extraction.

Porte-filtre_GaggiaClassicPro_SocietedesCafes

The ideal pressure level for squeezing coffee is around 30 pounds, but that's not as important as you might think, since the machine itself will impose 130 pounds per square inch of pressure, i.e. 16 bars. Above all, the coffee press makes your coffee uniform and removes the air between the beans, so that there is no water channel (channeling), which would make the extraction non-uniform.

Choosing the right coffee

Why do roasters indicate on their coffee bags that it is recommended for a particular infusion or espresso, while others are compatible with different infusion modes (omni roast) The darker a coffee, therefore roasted for a long time , the easier it is to extract with the espresso machine, because it becomes porous and brittle. This means that less water is needed to extract the coffee properly, but the subtleties of the fruit's notes are less able to be detected. That said, a medium to light roast may be fine for an espresso and give you more flavor, but you may need to brew your coffee at a higher temperature. The hotter the water, the more efficient the flavor extraction. If you prefer an espresso with a lot of body, a 1: 1.5 ratio would be desirable. If you prefer a mild and fruity espresso, use a medium roast coffee and a 1: 2 ratio.

Very light roasts are not recommended in espresso due to the very short extraction time, as the bean does not have time to develop its entire body and this will result in a sour, grassy and simply unpleasant espresso.

Be patient, espresso is probably the most intolerant method of preparation. In addition, a few seconds more or less than the target time or a gram of coffee too small in the portafilter is enough to have devastating effects on the taste of your coffee.

The secret: consistency! If you need to make any adjustments, start with the size of the grind, because that will affect the rest.

Base ratio for an espresso:

  • 18 grams of coffee
  • 36 grams of liquid for an extraction time of 29 seconds
  • Temperature 94 C (201 F)F)


Accessories for espresso machine:

Machines 

Automatic mills

Balance

Coffee press

 

Espresso-type coffees

See the coffees offered for espresso type

 

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1. The World Atlas of Coffee - James Hoffmann
2.https://kitchenboy.net
3.https://perfectdailygrind.com
4.Filter_Brew_Guide_Onyx