How to Identify Extraction Issues by Examining Espresso Crema?

As more people develop the habit of drinking coffee daily, home coffee corners have become a popular trend in households. FrontStreet Coffee frequently receives questions about issues that arise when making coffee at home. Among these, espresso crema is one of the most common extraction concerns that our customers focus on. Today, let's dive into this topic.

Is the "crema" in Espresso actually oil?

When we let freshly extracted espresso sit and observe carefully, we can see that the lighter-colored layer on top consists of countless tiny bubbles. These bubbles form because the coffee machine's pressure during extraction is sufficient to cause insoluble oils from the coffee grounds to encapsulate carbon dioxide. In Italian, it's called "Crema," while most baristas in China habitually refer to it as "油脂" (oil).

If you let the extracted shot sit for an hour or so, the carbon dioxide gradually dissipates, and the crema subsequently breaks down. At this point, you can see a layer of obvious reflective substance floating on the coffee liquid – this is the actual coffee oil in the truest sense.

How to achieve beautiful crema in Espresso?

Quality crema appears golden-yellow with a delicate surface and uniform color. When swirled, it moves as smoothly as cream with noticeable adhesion to the cup walls. Not only does it provide excellent visual appeal to the espresso, but it also enhances mouthfeel and aroma when tasted, protecting the coffee's flavor. When making hot milk-based coffee drinks, it also facilitates latte art fusion and supports pattern formation. Perhaps these are the reasons why people go to great lengths to pursue the perfect espresso!

Based on our extraction experience, to achieve rich crema, you should prioritize coffee beans with high oil content and sufficient carbon dioxide, such as medium-dark roasted beans within their optimal tasting period (45-60 days), or fresh espresso blend beans containing a certain proportion of Robusta. Once you've selected suitable coffee beans, you also need to combine them with fresh grinding, stable high temperature, sufficient extraction pressure, plus reasonable extraction parameters. Satisfying these key factors is essential to obtaining espresso rich with dense crema.

Overall, the fresher the beans, the deeper the roast, and the greater and more stable the equipment's pressure, the better the coffee crema will perform. Next, FrontStreet Coffee will teach you how to determine the state of espresso by observing crema characteristics, thereby solving various common extraction problems.

No crema at all, or thin crema

The problem likely lies in beans that have been stored for too long (including improper storage and coffee beans that have been pre-ground). The longer the storage time, the more gas exchange occurs between coffee beans and air, resulting in more carbon dioxide loss and ultimately less coffee crema. Additionally, insufficient coffee machine pressure, low temperature, too coarse grind, inadequate tamping pressure... these are also causes of insufficient coffee crema.

White-ish crema

If your extracted espresso has decent crema thickness but lacks golden color and the overall taste tends toward sharp acidity, it's likely because you used beans with a lighter roast. For example, when FrontStreet Coffee uses Kochere coffee beans, which primarily highlight fruity acidity flavors, to make espresso, failure to find the right grind size can lead to under-extraction, resulting in unpleasant acidity and astringency in the coffee, accompanied by lighter-colored crema.

Coarse, bubbly, and clumped crema

This type of espresso crema typically shows obvious "lumpy" texture, often lasts for a very short time, dissipates quickly, and has poor fluidity – much like over-foamed milk that's difficult to spread and incorporate.

This is caused by coffee beans that are too fresh with excessive gas content. Freshly roasted beans contain large amounts of carbon dioxide. When large quantities of gas are forced into the coffee liquid, the emulsified oils cannot completely encapsulate them, resulting in the phenomenon of bubbles bursting first and then forming clumps. Once returned to normal temperature and pressure, these unstable bubbles quickly break down over time. If you encounter this situation, FrontStreet Coffee recommends letting the beans rest before extraction (7-10 days).

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FrontStreet Coffee

No. 10, Bao'an Qianjie, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

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Tel:020 38364473