What does arabica mean when espresso crema is thin or missing?

Crema forms when oily compounds in coffee wrap around carbon dioxide bubbles, so a thin or absent layer points to a problem somewhere in the process. The usual suspects are bean freshness, roast level, extraction degree, coffee variety, grind size, water temperature and machine pressure. A full crema should cover the dark liquid, take up about a third of the volume and cling to the cup wall.

Arabica meaning is relevant here because variety drives how much crema a bean can produce, and different varieties express different traits in the cup. Freshness matters just as much: richer crema generally indicates fresher beans, while a darker crema color shows more dissolved solids in the liquid. Roast level follows the same logic, with darker roasts tending to show more prominent crema, so troubleshooting starts with beans and works toward the machine.

The golden, dense layer of crema on the surface of an espresso is often regarded as an important sign of a successful extraction. Many coffee enthusiasts find in practice that the espresso they brew either has thin crema or none at all. This may involve multiple factors such as the freshness of the coffee beans, the roast level, the variety selected, the grind size, the water temperature, and the pressure of the espresso machine. Front Street Coffee has sorted through these common confusions regarding the various factors that may cause a lack of crema, and combined with the recipe approach of classic espresso blends, helps everyone troubleshoot the problem one by one, so that every cup of espresso can present an ideal state of crema.

Recently, quite a few friends have consulted Front Street about espresso extraction problems, among which missing or overly thin crema is the most frequently mentioned situation. For a qualified espresso, that layer of golden crema can be called the soul, so Front Street decided to systematically sort out exactly which reasons can cause no crema to appear during extraction.

An espresso in its ideal state should have a layer of golden crema covering the dark coffee liquid, accounting for about one third of the total volume, presenting a creamy texture when gently swirled, and clearly clinging to the wall of the cup.

Normal espresso state

If the brewed coffee has no crema at all, it means something in some step has gone wrong — it could be the beans themselves, the condition of the equipment, or possibly the parameter settings or operating technique.

What factors affect crema?

a. The freshness of the coffee beans

The formation of crema is the result of the oily components in coffee wrapping around carbon dioxide bubbles, so the amount of crema can in turn be used to judge whether the beans are fresh — the richer the crema, the fresher the coffee beans usually are.

b. The roast level of the coffee beans

On the premise of consistent freshness, the more prominent the crema performance, the more we can infer that this bean has a darker roast level.

c. The extraction degree of the coffee beans

The darker the color of the crema, the more dissolved substances have entered the coffee liquid.

d. The variety of the coffee beans

Different coffee varieties bring different trait expressions, thereby affecting the amount of crema produced. It is currently known that Robusta produces more crema than Arabica. Precisely because of this, when developing Front Street's classic espresso blend coffee beans, the roaster added about ten percent Robusta beans on the basis of the original "Mamba recipe" in order to obtain denser espresso crema, which not only enhanced the coffee's full-bodied feel and burnt aroma, but also created the necessary conditions for latte art through that layer of golden crema.

e. The pressure of the espresso machine

The reason an espresso machine can extract rich golden crema lies at its core in the 9-bar extraction pressure; the greater the pressure, the richer the crema.

Front Street has sorted out several common causes for everyone to compare and refer to.

① The coffee beans are roasted too light.

The coffee beans commonly seen on the market are broadly divided into beans for pour-over drip brewing and beans for espresso machines. The former are mostly single-origin beans with a lighter roast; the latter are mainly blend recipe beans, along with single-origin SOE, generally with a darker roast.

Crema effect of light-roasted coffee: relatively thin, with a lighter yellow-white color

Overall, the darker the roast of the beans, the richer the crema performance. If you use single-origin beans meant for pour-over to make espresso, the crema tends to be on the thin side, so be sure to check the intended use when purchasing.

② The coffee beans are no longer fresh.

If the extraction state appears normal, then it is very likely the beans are not fresh enough. Espresso machines are actually quite picky about the state of the beans: beans that are too fresh produce unstable crema during extraction, tend to form large bubbles and dissipate quickly; while stale beans produce almost no crema at all.

Espresso extracted from stale coffee beans has scant crema

Usually the resting period for espresso beans is about 7 to 10 days, meaning that starting from the seventh day after roasting, the extraction state gradually stabilizes. The optimal flavor period for espresso beans is about 60 days; after more than two months, the aroma and flavor are basically all lost, and the amount of crema also drops significantly. (This conclusion is based only on normal storage conditions; Front Street has not yet tested nitrogen storage.)

③ The pressure of the espresso machine itself is insufficient.

This problem is relatively common in home machines. The reason we can extract thick crema is that the espresso machine's 9-bar pressure forces the essence out of the coffee puck. But some small espresso machines cannot provide a stable 9-bar extraction pressure, so naturally they cannot press out rich crema.

④ The coffee grind is too coarse.

Grinding too coarse will likewise lead to crema that is not rich. This situation is easy to identify: the flow rate during extraction is extremely fast, accompanied by spurting from channeling, the crema color is light and thin, and the espresso tastes weak. You can use 20 seconds as a reference standard: if a double shot's worth of coffee liquid is extracted in less than 20 seconds, then it is very likely the grind is too coarse.

The extraction process is a total mess

⑤ The water temperature is too low.

Nowadays many new-style espresso machines have a manual temperature adjustment function. The suitable water temperature for extracting espresso is generally around 93 degrees Celsius; if the temperature is too low, it may also prevent crema from appearing.

Another situation commonly encountered with home machines: it may take 10 minutes or even longer from powering on to completing the heating. If extraction is carried out before it has fully heated up, it is very likely that crema cannot form due to insufficient water temperature, and the coffee taste will also tend toward sharp acidity.

The above content is compiled by CoffeeHunters, a coffee news website.