Espresso Introduction
Fundamental Brewing Concepts
Coffee as a beverage can be served in a multitude of ways. Coffees can be hot, cold, blended with ice, light, strong, with or without milk, or, with or without sugar. It's important to realize that though coffee can be SO diverse in its presentation, all coffee beverages begin as simply coffee and water.
To create any coffee beverage you must first take coffee beans, mix them with water, and get coffee-flavored water. There are only two fundamental brewing concepts to achieve this result.
The first is the "pass-through" concept. Using this concept, we take beans and pass water through the beans, as the water passes through the beans and comes out at the other end, the water extracts the coffee flavors from the beans and becomes coffee-flavored water.
The second brewing concept is the "soaking" or "immersion" concept, putting coffee and water in a container and allowing them to soak or steep, then straining the mixture to create coffee-flavored water.
Brewing Variables
While there are only two conceptual ways we can brew coffee, there are several variables that affect the result of the brew. Each of the following things will affect the brew result and consistency:
1. Grind Particle Size - The shape, size, and consistency of the ground particles of coffee used.
2. Brew Time - The amount of time that the water and the coffee spend in contact with one another.
3. Dose - The amount of ground coffee used. (ideally weighed)
4. The Ratio - The amount of water vs. the dose. (Eg. A 1.2 ratio means that for every 1g coffee used, 2g of water is used)
5. Temperature - Of the water that is used to make the brew.
6. Water Cleanliness - The volume of impurities in the water used to brew. (Eg. odors and colors)
7. Minerals - In the water used to brew.
8. Turbulence - The agitation, mixing time, and amount of force used to control how evenly the water and coffee interact with one another.(typically considered in the immersion brew concept).
9. Pressure - The force with which the water is pushed through the coffee. (typically with the pass-through concept of brewing)
10. Flow Rate - The amount of water that is added per second while brewing. (typically observed in the pass-through concept)
11. Freshness - The roast date and grind date of the coffee being used.
12. Equipment Cleanliness - Equipment that is not properly cleaned will affect the quality and consistency of the brew.
Each of the above variables affects the sensory result of a brewed coffee. Some have a subtle effect while others have an aggressive effect.
Methods of Extraction
As we mentioned above, there are only two conceptual ways that we can brew coffee (Pass-through/immersion). However, there are many methods and devices we can use to brew coffee.
Each of these devices exists because they affect the brewing variables differently and allow you to control different aspects of the above variables. It's rare for an extraction method to use both of the brewing concepts, but not unheard of.
Of the devices listed below, some have limited ability to control and adjust the variables (eg. french press) whereas others have much more detailed and precise control of the brewing variables (eg. espresso machine).
Here is a list of some of the more common extraction methods/devices:
Cupping
Ibrik
Cold Brew
French Press
V60
Perculator Machine
Siphon
Aeropress
Phin Coffee (Vietnamese filter)
Moka pot
Espresso Machine
Definition of espresso
Websters: espresso. Merriam-Webster's Word of the Day for November 3, 2012 is: espresso • \eh-SPRESS-oh\ • noun. 1 : strong coffee brewed by forcing steam through finely ground darkly roasted coffee beans 2 : a cup of espresso.
Wikipedia: Espresso (/ɛˈsprɛsoʊ/ (listen), Italian: [eˈsprɛsso]) is a coffee-making method of Italian origin, in which a small amount of nearly boiling water is forced under pressure (expressed) through finely-ground coffee beans.
Espresso Extraction process
Hot water (heated to a precise temperature) is forced (using pressure) through a compressed dose of finely ground coffee. The compressed finely ground coffee ensures that the water passes through slowly even though it is pressurized.
As the heated water slowly passes through the compressed dose, it comes into contact with the ground coffee, extracting the soluble compounds (particles in the ground coffee that can be dissolved in water) coming out the other side as coffee-flavored water, albeit, of a concentrated variety.
Crema
The process of forcing pressurized water through coffee causes all the trapped carbon dioxide in the coffee grounds to escape. This reaction creates small bubbles that form a layer of what is called "Crema" on top of your espresso. These small bubbles are covered in coffee oils and flavored water which causes them to appear light brown.
The Crema on an espresso used to be used as an indicator of quality. While crema can certainly reveal some things about espresso, it's only one indication, analyzing crema as a sign of quality is not an effective diagnostic tool to improve an espresso recipe in most cases.
The only thing that Crema is effective at determining, is how fresh the coffee is. As roasted coffee ages it loses carbon dioxide, and since Crema is made up of carbon dioxide, the amount of crema on an espresso directly correlates to how long ago the coffee was roasted. If the coffee has lots of bubbly Crema (which tends to dissipate quickly) the coffee is very fresh, whereas if there is limited-to-no Crema, you can be sure the coffee has aged significantly. Of course, there are varying degrees of Crema's appearance in-between that aging scale.
It is important to pay attention to coffee that is too fresh, Crema will help in determining this. If there is a LOT of Crema it means the coffee has too much carbon dioxide, this negatively affects one's ability to brew espresso consistently and accurately. In such cases, the coffee should be rested longer before being used. Additionally, Crema should also be used to recognize when coffee is too old and stale (espresso with little-to-no Crema) as you will instantly know after brewing whether it is even worth drinking (stale espresso has less complexity and is often very dull).