Why does coffee have to be freshly ground?
If the diameter of coffee powder is doubled, the volume of individual particles is reduced by 1/8, and the surface area of the total coffee powder is doubled accordingly. After coffee beans are ground into coffee powder, their surface area increases exponentially, and the area in contact with air increases hundreds or thousands of times.
Roasted coffee beans contain extremely important acidic fat and volatile fat once they come into contact with air, they will undergo biochemical changes and taste and aroma will deteriorate. Esters and aldehyde enzymes in coffee aroma compounds are the most volatile, which will make coffee taste worse after evaporation.
Not only is the volatile loss of aromatic substances, but oxygen in the air also oxidizes aromatic components, especially fats, producing a rotten smell. Freshly ground coffee quickly absorbs moisture from the air, adding weight and reducing the effectiveness of the extracted coffee ingredients. Internal molecular pressure complicates matters further.
Therefore, the coffee powder bought in the store for a long time can only be used as coffee "mummy fragments", because the coffee powder loses a lot of flavor; in order to have a good cup of coffee, you must not buy coffee powder conveniently.
In addition, even if it is roasted coffee beans, coffee aroma is also very easy to emit, roasted coffee beans that are well preserved for more than one week to two weeks, are already not fresh, so not only fresh ground, but also as far as possible to choose fresh roasted coffee beans.
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Talk about the powder pressing technique of espresso
This is the biggest variable, because our body is not an instrument, the strength of pressing powder is based on the feel, there is no feel for the novice, only powerful and small, even for the veteran on the bar, the first or second cup every day is to find the feeling of strength, because we may directly affect the exertion of strength because of our physical state and even mood on that day. The reason for this is to adjust the strength of powder pressing.
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Experience the different tastes of coffee
The color, aroma and taste of coffee are caused by some complex chemical changes that take place during the baking process. Generally speaking, we use strong alcohol to show the round, mellow and strong taste of coffee.
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