What is Crema? The Beautiful Lie Atop Your Espresso

What Is Crema? The Science Bit

Crema is the reddish-brown foam that rests on top of a shot of espresso. It's formed when hot, high-pressure water is forced through finely-ground coffee. This process emulsifies the oils in the beans and suspends them in a colloid of tiny, microscopic gas bubbles—mostly carbon dioxide (CO2).

So, in simple terms, crema is a foam of coffee bean oils and carbon dioxide. Its presence is unique to the espresso brewing method due to the intense pressure involved. You won't find true crema on a cup of filter coffee.

What Crema Tells You About Your Coffee

While it’s not the only indicator of quality, the color, thickness, and stability of the crema can offer clues about the coffee and how it was brewed:

• Freshness: Freshly roasted coffee beans contain a lot of trapped CO2. As the beans age after roasting, this gas slowly dissipates. A thick, rich crema is often a sign that the beans are fresh (typically within 1-3 weeks of their roast date). No crema, or a very thin, pale crema, can indicate stale beans.
• Roast Level: Darker roasts tend to produce a thinner, darker, and less stable crema because the roasting process forces more oils to the surface of the bean, making them more fragile. Lighter roasts often yield a lighter-colored, more stable crema.
• Bean Type: Robusta beans produce a thicker, more stable, and often darker crema than Arabica beans. This is because they have a higher CO2 and fat content. Many traditional Italian espresso blends include a small percentage of Robusta specifically for this reason.

Tips for a Better Crema

Struggling to get a good crema at home? Here are a few tips:

1. Use Fresh Beans: This is the most important factor. Buy beans with a roast date printed on the bag, and aim to use them within a month of that date.
2. Grind Fresh: Grind your beans immediately before brewing. Pre-ground coffee loses its volatile oils and CO2 very quickly.
3. Find the Right Grind Size: For espresso, you need a fine, consistent grind. If your shot pulls too fast (under 20 seconds), your grind is likely too coarse. If it chokes the machine (over 35 seconds), it's too fine.
4. Tamp Evenly: Apply firm, level pressure when tamping the coffee grounds. This ensures the water flows through the puck evenly.
5. Check Your Machine: A good espresso machine needs to deliver water at a stable temperature (around 90-96°C) and high pressure (ideally 9 bars).

The "Beautiful Lie"

So, is a perfect crema the sign of a perfect espresso? Not necessarily. While it's a good indicator of freshness and proper technique, it doesn't guarantee taste. You can pull a shot with a beautiful, thick crema from over-roasted, bitter beans. Conversely, some exceptional single-origin light roasts might produce a thinner crema but taste incredible.

Ultimately, crema is an important part of the espresso experience—it contributes to the aroma and the velvety mouthfeel. But the final judgment should always come down to what's underneath it. Use the crema as a clue, but always trust your palate as the final judge.