Espresso Crema: Important or Not?
Espresso Crema refers to the trapped gas bubbles that make a thin layer suspended on the top of a cup of espresso. If it is the right color, consistency and thickness, crema is considered a hallmark of high quality espresso. It can also be a telltale sign of problems with the espresso.
Is Crema Important to Espresso?
Answering this question depends a lot on who you ask and how they like their espresso. It is true that good quality crema enhances the appearance of the espresso. When you think of the picture perfect cup, it has good crema on top. Since crema is composed of gas bubbles, it plays a great role in aromatics. As these bubbles pop and fade they release their rich coffee aroma. If you drink your espresso straight, while the bubbles are still on top, then good crema also enhances the feel of the drink on your lips. The taste of the crema is usually sharper than that of the espresso itself, so the crema can add an appealing flavor variance to the drink.
That said, there is no perfect crema for everybody. Changes in crema are often signs of differences in how the espresso was made. Sometimes there is an obvious problem, but other times it is simply a matter of taste. Since crema has a much greater effect on the appearance of the espresso than the taste, it is important not to dwell too heavily on the crema. If the espresso tastes the way you like it, then the appearance of the crema is secondary. If you mix your espresso with milk in a latte, then the crema will be overpowered by milk foam anyway, and will be largely irrelevant.
Common Types of Crema and Their Causes
A very light crema color that is almost tan or yellowish is an indication of under-extraction. The espresso was pumping faster than it should be. This can result in a weaker cup of espresso. You can fix this problem by using a finer ground or a firmer tamping that will make the coffee more solid.
Thin and Dark Crema
Crema that is noticeably thin or very dark is a sign of over-extraction. The espresso was not pumping out as fast as it should be; therefore the crema was not able to truly develop. This also results in a stronger cup of espresso that may be too bitter, but may also be just what you want. Just opposite of the treatment for under-extraction, use a coarser ground and a less firm tamping.
Short Lasting Crema
Ideally, crema should remain healthy and visible for about two minutes. If the crema is fading away after one minute, then this is usually another sign of fast extraction, but is also common when using light roasts. Remember that true espresso roast is very dark, but if you prefer light roast espresso go for it, and just keep in mind you will probably have short-lived crema.
Oil Globules or Graininess
These two conditions are the only ones on the list that represent a true problem with the espresso. If there are large globules sitting on top of the espresso, and it took an exceedingly long time to extract, then it was far over extracted. This type of espresso is usually undrinkable and must be redone. It looks ugly, and it tastes ugly. If you find granules of coffee in the drink, then the grind was so fine it was pumping through the espresso, and a courser ground should be used. Not many people like drinking coffee grounds.
The importance of crema is largely an individual preference.
How important is crema to you?
I would love to get some ideas of how people like their crema in the comments below.