Analysis of Italian espresso oil Crema concentrated crema light color Italian blend blue mountain style

What is crema? Why did crema disappear?

Coffee roasting involves a complex series of chemical changes that produce large amounts of carbon dioxide. Most of the carbon dioxide is naturally emitted during storage of coffee beans, but there will still be more carbon dioxide remaining in the cell wall.

9 bar pump pressure dependence is the largest emulsion coffee insoluble oil. In fact, water pressure also has another effect, that is, to make water supersaturated with carbon dioxide, increasing the solubility of carbon dioxide in water, thus dissolving more carbon dioxide than at ordinary natural pressure. That's why thousands of tiny bubbles form when hot water passes through the cake.

Foam formation requires bubbles, and compounds or particles that like to surround these bubbles to stabilize the structure of these bubbles and make them more elastic. The coating effect of these chemicals involves surfactants. The formation of vesicles is mainly related to melanoid. Melanoids are a group of compounds formed during coffee roasting that scientists know little about.

Proteins and melanoids coat bubbles because they have components that repel water-also known as hydrophobicity. So they go to gas rather than water, and eventually these substances are adsorbed onto bubbles due to their hydrophobicity, forming a bubble layer.

There are other hydrophobic substances present in coffee: fats/oils. The fat here is separated because fat is the solid form of oil, and in coffee both forms coexist.

Crema disappears due to both grease/oil and gravity. Surfactants dissolve in water, and gravity pulls down the coffee substance in the foam layer, which pulls down on the substance covering the bubble surface, causing the bubble to become weak and inelastic, and eventually burst quickly.

The rate at which the foam layer disappears depends largely on how quickly gravity acts. A cup of properly extracted concentrate will last longer than a cup of poorly extracted concentrate. This is because a properly extracted concentrate has a heavier overall composition, which can be confirmed by the touch of the concentrate in the mouth.

Crema's Color: What Can It Tell Us?

Crema should normally appear reddish brown, but what does it mean when concentrated crema is lighter or very dark, almost charred brown? Part of the answer has to do with concentration itself. Because crema is a bubble of carbon dioxide trapped in a concentrate, if the foam layer looks dark, we can usually be sure that the concentrate will be dark, too.