Sweetness and Intensity of Espresso Shot Embodied in Golden Crema
When you pull a shot of espresso there should be a thin and foam, golden-brown layer on top which is just slightly foamy and very sweet - this is the Crema.
The chemical composition of the crema includes sugars, proteins and emulsified oils. The espresso crema is formed to due gases dispersing at very high pressure in the liquid during the expresso extraction process. These gases include air and carbon dioxide.
Why is the Espresso Crema important?
Crema is important because it is comprised of the finest tastes and aromatic qualities of the coffee. The crema sits atop the espresso shot and helps to retain the fine intensity and flavorful qualities of the espresso shot.
Troubleshooting the Espresso Crema - Over Extraction and Under-Extraction
For example, if the crema begins to turn from golden-brown to a whitish color during the extraction of the shot, then it means that all of the good oils in the coffee beans have already been extracted. Any further extraction will cause bitterness and an acidic quality that harms the flavor of the shot.
Under-Extraction and Poor Coffee Quality Affect Crema
If the quality of the crema is poor and the color is not golden brown then it may be the result of under-extraction which produces a weak and water shot. Sometimes a poor crema is the result of old and stale coffee that has been stored improperly.
The quality of the espresso crema can also be affected by the brew temperature. A brew temperature that is too low will produce a poor espresso crema, and this brew temperature may also be affected by the failure to pre-heat the espresso machine portafilter as well as the demitasse.
Proper Tamping Crucial to High Quality Espresso Crema
In addition the coffee in the portafilter must be tamped it properly and follow all of the other correct espresso technical specifications. during brewing. This includes the proper extraction time for the brewing of the espresso shot.
Some Facts About Espresso Crema
The color of a fine crema may vary a bit depending upon the coffee beans used. Typically a fine crema will range from golden-brown in color to slightly brownish-red.
The crema atop an espresso shot is comprised of vegetable oils along with sugars and proteins.
Layers of an Espresso Shot
A fine espresso shot is divided into three layers, the heart at the bottom, the body in the middle and the crema on top.
The body of the espresso shot should be a caramel brown color while the heart should be a deep and rich brown color. The heart typically contains most of the bitterness of the shot that balances out the overall sweetness of the shot including the crema.
Espresso Ideal for Blending: The intensity of the crema and the overall concentration of flavors in an espresso shot is what makes it ideal for use in espresso drinks blended with steamed and frothed milk.
Controlling Variables of Espresso Brewing for Optimal Crema
If you have not correctly controlled the espresso pulling variables - e.g., brewing temperature, grind size, tamping pressure, extraction time, etc. - then a crema may not form atop your shot in which case you will be missing out on some of the coffee's finest qualities.
The espresso shot should be about one-tenth crema or slightly less. Crema not only contains the intensity of the espresso shot and its finest aromatic qualities, it also provides the lingering finish, or aftertaste.
Scientifically speaking, crema consists of an amalgam of gas bubbles which suspended within a liquid film possessing very high surface tension between molecules of water.
Crema - Essence of Espresso Shot Expressed in Crema continued:
A Quality Espresso Crema Is Compact and Persistent
A fine crema will persist atop the espresso shot and not immediately dissipate. It should be compact enough to maintain its composition for at least two minutes.
Eventually the suspended water molecules will drain away and the trapped gases will be released. You will know when this occurs because you will be able to see the espresso beneath the crema.
Causes of Under-Extraction Thwarting Optimal Espresso Crema
An overly light-colored crema (e.g., lightish tan to yellow in color is a sign of under-extraction, possibly due to low brewing temperature, insufficient tamping or too course of a coffee grind size.
A good rule of thumb is to let the coffee “rest” for 48 hours after roasting. Make sure the coffee is in a cool, dark and dry place, and not the freezer or refrigerator.
Espresso Crema Tips - Symptoms of Over-Extraction
Conversely, over-extraction may show up as a very dark crema, often with a tan dot in the middle.
You may have noticed that it took too long (e.g., ten seconds) for the espresso to begin pouring out of the spout during brewing, and the overall shot took longer than normal (e.g., longer than 26 seconds).
Causes of over-extraction may include too firm of tamping, or too fine of a coffee grind. One way to know if your grind is too fine is if there is grit at the bottom of your demitasse after you consume the espresso shot.
Another cause of over-extraction is using too much coffee. A good range to stay within is between six and eleven grams of coffee for one espresso shot. Over-extraction may also be signaled by an extremely thin crema consisting of large globules of oil.
Diagnosing Under-Extraction to Maximize Espresso Crema Intensity
If the extraction of the espresso shot occurs too swiftly, or perhaps if the roast is too light, you may diagnose this by allowing the espresso shot to sit for about one minute and see if the crema (which may have the proper color) begins to drop about one-fourth inch down in the cup.
Another sign is that there are overly large and unstable bubbles within the crema, or the color is too pale.
Some people like to put a small amount of Robusta coffee in their espresso blend (rather than using exclusively the finer Arabica Coffee varietal. While this may create a heartier crema, it may also fade quicker than the pure Arabica espresso shot.
Essence of Espresso Shot Essence Expressed in Crema continued:
Signs of a Perfect Espresso Crema
When you gaze upon a perfect espresso crema you will notice not only how the thin foamy layer is very tightly compacted, but also that there may be some dark striations which some refer to as a “tiger skin” appearance.
This fine crema will allow you to enjoy the true purpose of espresso, a robust shot with a fine intensity and abundant flavors and aromas.
A bitter and acrid quality in an espresso shot may result from a dirty espresso machine. Coffee oils grow rancid when they build up on brewing equipment. Remember, cleanliness is next to godliness!
Coffee Processing and Espresso Crema
In general a dry-processed Arabica Coffee will tend to produce a better Espresso Crema than a wet processed coffee because the dry-processed coffee has a greater percentage of fats, lipids, proteins, soluble solids, minerals and sugar.
A dry-processed coffee may also may have remnants of the mucilage of the coffee cherry, whereas this has been washed off more completely in wet-processed coffees.
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