Espresso is nothing more than coffee that is brewed a certain way. It is finely ground to almost a powdery consistency then almost boiling hot water is forced through the grounds under intense pressure.
This brewing process is timed so that the flavorful and aromatic oils are extracted from the coffee and not the bitter components. The results are a full-flavored, strong but not bitter, concentrated shot of coffee.
Espresso Brewing ProcessThe Dose and the Tamp:
The dose is the amount of ground coffee deposited into the portafilter. Typically, about 8 grams (approx. 2 tablespoons) is used for a single shot and around 16 grams for a double. Most portafilters have a fill line which indicates the proper amount (after compaction) to use.
The compaction of the grounds is known as the tamp. This is accomplished with a round, weighted tool that is flat on the bottom and is also referred to as a tamp. First, run hot water through the portafilter so the cold metal will not cause the brewing temperature to be lowered.
Fill the portafilter with the ground coffee and tamp the grounds with an even, downward, twisting motion. Then tap the sides of the portafilter causing the coffee on the sides of the portafilter to fall off of the side wall. Tamp again until an even, level and firm compaction is accomplished.
If the grounds are not firm and level, the pressurized water could blast a hole through the grounds and the water would follow the path of least resistance and not pass through all of the grounds evenly. This would over-extract the grounds surrounding the hole(s) and under-extract the other grounds.
Now brush any coffee on the rim of the portafilter to ensure a snug fit before placing back on machine.
Extracting the Espresso:
First thing you’ll need is a clear shot glass with marks for 1, and 2oz. With the tamped grounds and the portafilter locked in the espresso machine and the shot glass in place, hit the brew button.
After a couple of seconds, the espresso should slowly start to fill the glass. As it is pouring, the streams should look like the consistency of maple syrup and be about the size of cooked spaghetti.
The ideal brewing time for a 1 oz. single shot of espresso is about 22 seconds from the time the brew button is pressed. If it reaches the 1oz. mark before 19 seconds or after 25 seconds, it’s best to pour the shot out and start over.
If the brew cycle was too fast, adjust the grind to be more fine or try tamping a little harder. If too slow, make the grind a little more course.
Trial and error is really the only way to tell if the grind is correct. Keep trying until it takes around 22 seconds to extract one ounce.
If a 1.5 ounce shot is desired, I use the same amount (4 tablespoons) as a double shot. Then the extraction time should be about 30 seconds.
A double shot should take around 38 to 40 seconds to brew.
The Crema:As the streams of espresso are pouring into the shot glass, observe its appearance.
After about a half an ounce, you should see a layer forming on top that is light brown in color. This layer is called crema. Crema is a fine celled foam of oils that have the best taste and aromatic properties of the coffee.
The perfect shot of espresso has a layer of crema that is thick, consistent in color and remains intact for at least a couple of minutes before settling.
Poor crema production is usually a sign of under-extraction but can also be caused by stale coffee, or a low brewing temperature from not preheating the portafilter.
A good test is to put a teaspoon of sugar on top of the crema. It should float for a few seconds before sinking into the espresso.
Another thing to observe during extraction is its color. Initially the color will be light brown in color, but after all of the good oils in the coffee have been extracted, the color will change to a whitish color.
If you notice a white ring forming on top of your crema, stop the brew. All of the good oils are extracted and this marks the beginnings of over-extraction which tastes bitter and acidic.
That's pretty much it! You can now call yourself the barista of the house (barista is the term used to identify the person who prepares the espresso in a coffee house).