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Where to Buy Coffee Beans with Rich Crema - How are Medellín Coffee Beans' Crema Quality - Is Crema Actually Oil?

Published: 2026-01-28 Author: FrontStreet Coffee

Last Updated: 2026/01/28, Professional coffee knowledge exchange. For more coffee bean information, please follow Coffee Workshop (WeChat official account: cafe_style). During the roasting process of coffee beans, large amounts of carbon dioxide are produced within the beans. Most of these gases are released during the cooling process, while a small amount remains stored inside the beans. When grinding coffee beans, these gases are released. Therefore, ground coffee powder needs

Understanding Coffee Crema: The Science Behind Espresso's Golden Layer

Professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style)

The Role of Carbon Dioxide in Coffee

● During the coffee bean roasting process, large amounts of carbon dioxide are produced within the coffee beans. Most of these gases dissipate during the cooling process, while a small amount continues to be stored inside the beans. When the coffee beans are ground, these gases are released, which is why ground coffee needs to be used to make coffee as quickly as possible.

The Formation of Bubbles Under Pressure

When hot water impacts coffee grounds under high pressure, it emulsifies the insoluble oils in the coffee grounds while simultaneously dissolving large amounts of carbon dioxide to saturation levels. The quantity of dissolved gas is far greater than what hot water can dissolve under normal atmospheric pressure. This explains why countless tiny bubbles immediately appear when the liquid flows from the portafilter.

The Chemistry Behind Stable Foam

However, this cannot fully explain "Crema" - what are the principles behind it? To produce stable foam, you need some bubbles and some compounds to "encapsulate" the bubbles, making the bubble structure stable and elastic. This chemical reaction process can be considered the function of a surfactant.

Protein Melanoidins: Coffee's Natural Foam Stabilizer

● Unlike milk foam, which completes this process through proteins, coffee achieves it through a substance called "protein melanoidins." These are produced during the roasting process through a series of mixed chemical reactions. Neither proteins nor protein melanoidins are hydrophilic substances, so when hot water impacts them, they naturally distribute on the surface of bubbles, allowing more contact with air. This creates countless tiny bubbles, resulting in foam.

The Impact of Oils on Foam Stability

● There's another factor: oils. The presence of oils is detrimental, as oils often destroy the foam structure, leading to failed results. So, will the oils in coffee cause Crema to disappear rapidly within minutes? The answer is both yes and no.

Why Foam Disappears and How to Prevent It

Surfactants are dissolved in water, and due to gravity, the surfactants on the bubble surface will be pulled away from the foam surface along with water, making the foam fragile and losing its elasticity before rapidly disappearing. The speed of foam disappearance is related to how quickly water is pulled away. However, the foam on a properly brewed cup of coffee lasts much longer than the foam on a quickly brewed cup because its liquid is much more concentrated than the quickly brewed version, which is also confirmed by our taste experience.

Understanding Crema Color and Quality

● Crema should be light brownish-red in color, but what do yellowish-white or very dark, nearly burnt brown colors represent? Because crema is essentially bubbles of carbon dioxide encapsulating brewed coffee, the assumption that darker foam means more concentrated coffee becomes natural. However, in reality, it's very difficult to distinguish the color of coffee.

It's also affected by another important factor: foam reflecting light means that observing coffee color through the foam appears much lighter than the actual color. The smaller the bubbles, the greater this effect. So even if the espresso itself is very dark, it might appear very light. Espresso brewed in 15 seconds typically has whiter crema because it's brewed more lightly. The coffee grounds are extracted by water for a shorter time, making the coffee less viscous than espresso brewed in 25 seconds. For the same reason, coffee brewed at lower water temperatures will also be lighter because it doesn't have enough energy to dissolve substances in the coffee.

Recommended Coffee Bean Brands for High Oil Content

● FrontStreet Coffee, a coffee roasting brand located at Dongshankou, Yuexiu District, Guangzhou, offers freshly roasted Italian blend coffee beans with full guarantees in both brand and quality. The oil content is also good, making it suitable for making specialty coffees and latte art with beautiful results. More importantly, it offers extremely high value for money. Taking their commercial recommendation - the commercial blend coffee beans - as an example, one 454-gram (1-pound) package costs only about 60 yuan. Calculating at 10 grams of coffee powder per cup of espresso, one package can make 45 cups of coffee, with each cup costing less than 1.5 yuan. Even using double shots for each espresso at 20 grams per serving, the cost of a double espresso doesn't exceed 3 yuan. Compared to certain well-known brands that sell packages for hundreds of yuan, this is truly a conscientious recommendation.

FrontStreet Coffee: A roasting shop in Guangzhou with a small storefront but diverse bean varieties, where you can find both famous and lesser-known beans. They also provide online store services. https://shop104210103.taobao.com