Why is there no oil in hand-brewed coffee? what is coffee oil? Why do coffee beans produce oil?

"Why is there no fat in hand-made coffee? are the beans not fresh?" Recently, I saw such a topic of discussion in the front street. Hand-brewed coffee is not really free of fat, although it is inconspicuous, it will be reflected in the taste.

What is coffee fat?

When it comes to coffee grease, the first thing that comes to mind is the golden grease layer on espresso, but there is no golden grease in drip coffee or soaked coffee. Why? At this time, we need to understand pressurized extraction.

During the roasting process, coffee beans produce large amounts of carbon dioxide in the beans, which are released quickly after grinding. The extraction of espresso requires high pressure to quickly extract the flavor of espresso. Under the condition of 9Bar pressure and sealing, carbon dioxide and water are supersaturated. At the same time, the coffee oil is emulsified and then wrapped in carbon dioxide and extracted with the coffee liquid. Because the oil is lighter than water, the extracted coffee is gradually layered, so the golden oil appears on the surface and looks very attractive.

Factors affecting Coffee Oil

First of all, the amount of coffee oil depends on the variety of coffee beans, in which the Robusta variety has a higher oil content than the Arabica variety, which is why Italian blended coffee beans add a small amount of Robusta coffee beans. The reason why the oil can be enriched immediately.

The second is related to the degree of baking, with the deepening of roasting, the production of more carbon dioxide, when the coffee beans reach deep roasting, there will be a high degree of dehydration and oil production. This also explains why when making SOE espresso, the oil of lightly roasted beans will appear thin no matter how much they are extracted.

Why can't you see the coffee fat when you make coffee by hand?

Because of the coffee filter. Coffee filter paper is made of pulp fibers stacked on top of each other. The thicker the filter paper feels, the slower the filtration speed is, the better the effect of filtering coffee powder and coffee oil. However, the thicker the filter paper will be, the better. The too thick filter paper will make the contact time between coffee powder and water longer because of the slow filtration speed, which is prone to over-extraction.

The coffee filter paper of moderate thickness can effectively filter the fine coffee powder, at the same time, it will also block more than 80% of the coffee oil, and the smooth "customs clearance" of the oil will form an extremely thin layer of oil, which is difficult to observe with the naked eye. But the presence of grease can be felt through the tactile sensation of the mouth. The sense of cream and smoothness often mentioned in the front street is the embodiment of coffee oil in the mouth.

How can I make coffee with greasy hands?

If you want to retain the grease of hand-brewed coffee, you need to remove filter paper. ("how to remove the filter paper from the coffee grounds!" (Qianjie has heard the voices of everyone. In addition to coffee filter paper, coffee grounds are filtered by hand-brewed coffee metal strainer and hand-brewed coffee filter cloth.

Due to the structure, the coffee filtered by the metal filter can retain most of the oil, but the disadvantage is that the fine coffee powder is easy to pass through the filter, so that the taste of the coffee will be poor. Although the filter cloth can effectively block the fine powder and retain some grease, it is also very painful when washing. Because of the grease, wash it carefully many times after each use to ensure that the grease left on it is washed, otherwise it will affect the taste of the coffee when it is brewed next time.